Do Performance Brake Rotors Have Better Cooling?

[@andrewnowakowski8572]

You did it wrong, when they say cooler they mean it looks better. a common mistake.

[@R53_trackaddict]

😂😂

[@sciroccoR]

haha

[@knitt9914]

LoL

[@vincentrohmann1110]

Lmao

[@21kpatriot]

Not only that, but the RIGHT front is on the LEFT side of the vehicle, so the "cool" factor isn't even there!

[@nickf6135]

I can see what it is that you did wrong...you had the winter air still in the tires. you need to drain the winter air and put in the summer air so it keeps the blinker fluid cooler

[@EngineeringExplained]

Kept winter air for a cooler garage.

[@flightheory4676]

Nick F Don't forget to add cold water to your engine.

[@stevelovesgod]

Robert Villapudua You must wait till the ambient temperature is 90+ F and the engine is warmed all the way up before you add ice cold water.

[@mrfrankcastle083]

SteveLovesGOD Wow.

[@drgreene1013]

It also help the muffler bearing run better and as a result the piston return springs make the engine more efficient

[@Spinattitude]

I know it takes a lot of work to do these tests, they are informative and interesting. Thanks for doing it!

[@mvnorsel6354]

Spot on , he does a great job, easy to watch.

[@bobbysenterprises3220]

I have heard that the slots or vents in performance rotors are not intended to cool the rotor. But rather to allow the vaporized brake pad gas off out from under the pad helping relieve brake fade. Also to help take heat out of the area between the pad surface and rotor not the rotor as a whole. Interesting test and your work into it is commendable. The smaller mass should have a faster temperature change rate. Heat up and cool down faster between applications

[@ukemike1]

In the past brake pad compounds would off-gas when they got hot enough. Those slots were to vent the layer of hot gas that was between the pad and rotors. Modern pads don't really do that, so the slots, and holes, are a marketing holdover. In budget endurance racing you'll find most cars, especially the fast ones, use blank rotors.

[@PROofHAPPYWHEELS]

@@ukemike1 I believe that's for longevity due to nature of endurance racing, not performance. Blank rotors harm the pads the least and also last the longest, but do not perform the most ideal.

[@dimasemko6334]

That's exactly what I was thinking while watching this video! The rotor itself isn't bigger than the OEM one, and there are no and additional ventilation holes in the tuned rotor, so he shouldn't have expected any performance improvements in terms of heat transfer from the rotor

[@kishka9886]

​@dimasemko6334 it actually cones down to mass VS surface area. The more surface area the more effective the heat transfer away from the mass. Those slotted brakes have lower mass and more surface area....that's about all it comes down too.

[@MrJethroB]

@@ukemike1 You're still going to have something between the pad and disc, whether that is a high pressure gas or just the ablated material of the pad. My pads are OEM atm which are flat but with drilled holes. The next set I'm going aftermarket discs with J hook/J curve and ferodo pads. All these performance pads, even if they don't produce lots of gases, do release more dust. Having a small surface groove in the disc gives the dust a space to collect thats not inbetween the two surfaces. More traditional deeper groves will do this too, but reduce the braking surface which is why you don't seem them so often in racing. Those discs are fine at road speeds and save a bit of pad wear but more area is the aim for performance. The smaller J hook style seems to be the best compromise from the people I've heard from, when you want to be able to rely on performance at high speed

[@collarbonecam]

I think this is just a result of testing parts intended for the track vs parts for the road. People convince themselves that race parts must be better on the road because they are designed for harsher conditions but this refutes that. Very useful as I am going to need new rotors in the future and with my car being an old Lincoln, I never really thought I'd need performance rotors, but I really wanted them. But it looks like you've saved me some money! It may be a tricky one to test but if you're considering doing it, how dusty performance pads get would be extremely useful as I think that is what will do more for braking performance.

[@EngineeringExplained]

Currently am running performance pads (swapped after this video). We'll see how they do with dust, but I don't know if the previous pads were stock or not (the ones used in this video, for both tests before and after), but they didn't seem to dust much. They did squeak, and these haven't much so far.

[@856Dropout]

Engineering Explained did you consider the pads would work more efficiently with the stock rotors because the surfaces of both were mated with each other?

[@tomtom255]

What kind of performance pads did you swap in after the test?

[@collarbonecam]

Dorito boy nope, it's a grandmother's Lincoln, not very desirable for what I think you might be imagining. But it does have an aluminator V8 which is what I desired.

[@shaggnar2014]

And to be fair these aren't even "race" parts, they're just shinny after market parts. Ask any Spec Miata driver what they use for rotors and they will tell you NAPA blanks. Why? Because they're cheap and work, rotors don't have to be anything fancy

[@trevorhoward3882]

As an ME this was a great video. Other factors to consider are friction as the stock rotors you tested looked to be used and the slotted rotors looked brand new. Generally rotors need to be "broken in" to the brake pads. If the same pads were used throughout the experiment they may have broken in to the stock set of rotors creating higher friction points on the slotted rotors. Incidentally came across this video looking for upgrades to my stock brakes.

[@EpicTurtle113]

Professionalism achieved dude

[@EngineeringExplained]

I'm so happy to be accepted!

[@DFWsCars]

He is my inspiration.

[@magnavox4794]

Along with looking almost 40 somehow...

[@Furantzu]

magna vox the fuck has that anything to do?😐 Does that somehow interfere with the fact that this guy is a complete pro?

[@RA1N93]

Engineering Explained The analysis is very good m8, nothing left to say but I would love to be doing tests like those

[@fromthegods78]

I once sprayed WD40 on the brakes to clean them so they will brake better. Forgot to clean it off. Massive surprise at first intersection

[@guthrie1181]

You cleaned your brakes with WD40? Did you hear they invented a thing called brake cleaner?

[@troytruong8246]

Rofl!!! I was 17 or 18. I did the same thing! My brake squeaks. I learned that w40 helps with the squeaky noise! Next thing i know. I almost ran through the garage! It didnt stop! I learned quick not to do that ever again! Lol

[@guthrie1181]

Troy Truong Yes, the squeaking generally implies you need to replace them, or use higher quality pads. It doesn’t imply your brakes are running low on oil.

[@lashlarue7924]

@@guthrie1181 Better question is, "how do I change the brake oil in my Camaro?"

[@guthrie1181]

Lash LaRue Bring your car to a mechanic immediately if that thought ever arises.

[@HenkkaWRC]

Learning physics hasn't ever been this much fun. You're the best "teacher" EE!

[@peterzebot1795]

It really isn't fun at all.

[@DENicholsAutoBravado]

I had perfectly fun Engineering teachers in high school and college. EE is an exceptional extension to what what they taught me, and my work on homework and math taught me. To call him equal to them is a high honor. I doubt they'd make as good of a KZbin video. That takes a lot of dedication to get good at, or natural talent plus lots of dedication will get you there faster - I should know. I've made videos for years and my production value stays lower, but I still love teaching and the conversations it makes.

[@DENicholsAutoBravado]

@@peterzebot1795 then why are you here? I used to take everything seriously. Take my advice. Have some fun. 😆

[@michaeld954]

Does the aftermarket breaks improve braking distance

[@DENicholsAutoBravado]

@@michaeld954 no. Under track conditions they're supposed to shed heat better and prevent brake fade. Stock brakes were already able to lock up the wheels so braking distance was more about tires and conditions of the road.

[@-jimmyjames]

the veins vent the pad gases away and prevent brake fade and essentially do a similar job to a wet tread tire pushing water center out. critically hot pads under pressure want to hover away from a flat rotor surface much like a hover craft generates thrust and hovers on its skirt. introduce veins, voila gaseous escapiest... anyone that races or drives very aggressively knows the sinking and sphincter puckering feel that is brake fade.

[@nordic5490]

james, bingo. I put 'j hook' (Willwood style) rotors on my car and the fade resistance was vastly improved on heavy braking over stock rotors.

[@mitchd949]

Yes, the surface grooves do that, but it doesn't matter which direction those grooves are clocked on the rotor. Foolish people think those grooves somehow have to spin a particular way as if they are scooping air the way a saw blade scoops wood chips when cutting wood. WRONG!

[@LukeBasson]

exactly. He should have measured the braking distance after repeated braking under high load. Not measuring temperature. But yeah he did that home work when cooling was in question. Pointless but done.

[@sidewinderzero]

@@LukeBasson to be fair to him, a big marketing point of drilled and/or slotted rotors is the "improved cooling" properties. So this is a good test for that factor. The brake fade and stopping distance properties should be done in another video

[@alangross2277]

@@sidewinderzero These are not drilled though. He doesn't seem to know the reason for the grooves, which are for the reason which James Alverson stated.

[@CaptainThirdGen]

nicely done test. Something to consider is that if the aftermarket rotors were brand new, perhaps they have a protective corrosion resistant coating (many rotors do for shipping) and these coatings usually take a while to burn off, and these coatings burn HOT. Just something to keep in mind.

[@Stian2001]

Breakclean and wipe with paper before install

[@Professor-Scientist]

​@@Stian2001dependsth ith it oil coated or coated in special lacquer 😊

[@netzoned]

@@Stian2001 Do not spray a brake cleaner (or any other semi-heavy to heavy) solvent, on a new, coated rotor! Some people will declare all kinds of stuff for cleaning new, coated rotors, such as there _will_ be metal particles in the rotor/braking surface that will get stuck in the brake pads. LOL! Now, there is no problem cleaning the brake surface area with light, soapy water, but that is a huge so-called preventative 'what if'. Does anyone really think a quality rotor will then have a quality coating applied to a rotor that has metal particles/shavings on it? To begin with, have any of you actually seen something like a CNC cutting metal? Bottom line: Buy quality rotors, coated or not, with quality brake pads! Also, any manufacturer that demands their rotors be cleaned has a quality control issue that has gotten back to them from consumers!

[@netzoned]

@@Professor-Scientist Clean is clean. And, anything that could have possibly been left on the rotor will burn off in no time. I am not going to get into all kinds of rotors from different manufacturers, but for instance, any _light_ oil put on a rotor for storage (until it gets to the consumer) is easily removed. And, entire _painted_ rotors that may be produced that way for cost savings, well, buy a better rotor! @CaptainThirdGen "protective corrosion resistant coating (many rotors do for shipping)" ... Nope. Manufacturers do not put a "protective corrosion resistant coating" for shipping. An actual, quality coating is used for climates, and conditions, I.E., such as road salt, to help protect against long-term corrosion. A quality coating will help to keep the rotor cleaner, such as in the vanes.

[@netzoned]

@@Professor-Scientist Oh, "special lacquer"? Maybe you are thinking of varnish?

[@UtwoBed]

Absolutely, YES. I drive my E350 van hard and I kept warping the rotors. I bit the bullet and bought a set of performance rotors and I've never had a problem since.

[@silenc3x]

Stock rotors might just be trash. You could have just bought blank centric premium rotors and had the same outcome.

[@DeadsupraEE3]

This and ChrisFix videos is all I need.

[@EngineeringExplained]

Chris is the man!

[@rscarawa]

Engineering Explained so it seems obvious to me that the temperatures would have been about the same for the type of test you've been doing. Why not actually get the brakes up to say 400 degrees and then roll the car out 1,000 ft and see what the temperature is like then? my guess is even if you do this test you'll find that the temperature difference at the end of the run doesn't show them but very much difference. I think that the all the tilted veins inside the rotors really do not blow off a significant amount more heat than the straight veins do.

[@flexican77]

@engineering explained... im not too science savvy, but even though you have certain controls, i think the variable veering test could be as simple as the engine bay heat transfer. Stock would be "cooler" and after changing out the rotors to slotted, the engine temperatures would still have a lot of heat. Just as you would need oil to cool down. so maybe the engine heat transferred to from the warmed up/hot engine, starting the slotted rotors out at a higher temp?

[@InvincibleExtremes]

that was pretty cool. especially since you included the data at the end.

[@johnruddy1596]

would have been been a better test if stock on one side and directional on the other..would go thru identical stress and heat transfer...both should have started at same temp within 2%

[@svtman21]

Actually, it was pretty HOT

[@chris74ify]

what side was the sun on? lol

[@DENicholsAutoBravado]

@@johnruddy1596 if the grab different amounts and push steering that could bias the brake one way or the other causing more heat on one side. I don't think running them at the same time would work unless their braking effectiveness is identical...and if they are then what's the point? 😉

[@EngineeringExplained]

This video is (possibly) a great example of confirmation bias. Because I think it's logical that the rotors have a better design, I did want to see if there's a reason for which they'd perform better than the stock rotors. Based on my data alone, I cannot confirm that, but I'm trusting that Science of Speed's data is accurate. Also, the sweat and grease stains are just make-up, you don't really believe I spent time in a garage working on a car, right? 😂 Follow on Instagram if you like to go fast! instagram.com/engineeringexplained/

[@johnd5805]

You have 1.3 M subscribers. Treat yourself and buy you a small window unit and one of them large super quiet box fans. You can take it with you when you leave or donate it to a little old lady who needs it.

[@BrienMalone]

Engineering Explained way too many variables in those tests. Too bad you can't stick it on a dynamometer in a room with controlled ambient temperature and some sort of hydraulic shunt to put the exact same amount of braking pressure each time.

[@AdamKlingenberger]

You nailed the analysis here. It's possible that the aftermarket rotors are designed to quickly reach a higher optimal temperature to increase efficiency, which would make them appear worse at low (and not dangerous) temperatures. Talking out of my ass here, but definitely if you are testing *performance* parts, the testing methods should replicate high demand events. If anything, this video demonstrates why people shouldn't be upgrading their car with expensive performance parts if they don't really know if it will help anything.

[@danieljensen2626]

Engineering Explained Yeah, I feel like you wouldn't have put so much extra work into analyzing the data or finding other people's tests if the aftermarket ones had come out as cooler right away. But with the mass difference your results do make sense.

[@AdamKlingenberger]

For example, Formula One tires would have very little grip at normal speeds. You have to run them high speed on a track to get them at optimal temperature.

[@christophereskridge9580]

How about actual performance? Like stopping distances, brake fade?

[@ThomasNing]

that wasn't the question being investigated, and would've made the video a lot longer, but if you're curious I'm sure there are many other videos investigating this already.

[@LtDan-ni5rw]

Better brake performance will generate more heat. Without testing performance in addition to heat, you're only concluding that the performance rotors generate more heat when braking. This would make sense if the performance rotors are doing say, 55% more work than factory. That said, to properly perform a cool down test both rotors would need to be the same starting temp and the vehicle would then have to come to a rolling stop without braking unless you could first conclude they are both providing the same effective braking. I'm interested in seeing that test in a future vid 😉 😉

[@ThomasNing]

Lt. Dan that's a good point actually.

[@giveme10feet]

Stopping distance is relevant, but modern-day standard rotors move enough heat to prevent noticeable brake fading. Back in the 50s most brake pads used asbestos as the padding to help u stop. So fading happened as braking increased. But this was also b4 vented standard rotors also which removes a lot more heat and gased each time u brake.

[@shaneebahera8566]

@@giveme10feet depends on how you are driving if you are drivinng like a maniac then you will notice it but normal day to day driving doesnt push brakes far enough to notice fading

[@EngineeringExplained]

A lot of folks asking about why I didn't test stopping distance since we're talking about brakes. Conveniently, my very first article for Road & Track explains why, and was released today! www.roadandtrack.com/car-culture/a10316984/why-braking-is-all-about-tires/

[@stevelinwood4397]

Engineering Explained great videos as always. However the point of these rotors maybe to dissipate heat quickly under extreme braking conditions. Your tests may not be doing the discs justice. Maybe find a way of recording temperature under extreme load a try again. good luck 😎

[@Henchman1977]

Did you weigh the rotors?

[@Henchman1977]

Nevermind... I asked the question seconds before you got to that part...

[@lvr1028]

Engineering Explained I think the wheels themselves are maybe in the way of the airflow through the rotors since they draw air through the front. Would mounting different wheels maybe make the rotors more efficient? Maybe you could also measure the temperatures inside the wheel well and the ambient temp and see if the stock rotors are actually drawing in warmer air. I'd think they aren't and that the outside and inside air temp differences while moving would be the same. Measuring the car while stopped id say the inside air would be hotter. Than the inside air but only because it's trapped. But while the car is in movement it's being cycled out. So that might be a factor that make drawing air from the outside negligible

[@RadioactivFallout]

Test was flawed, maybe. You didn't weight the rotors. If the stock one are, let's 2 times heavier, they will absorb more heat and heat slower. Is like boiling water. If you apply the same heat and boil in the same pan 1 liter of water and 2 liter, 1 liter will boil faster. That's why MAYBE, it is an error. How big is the difference in weight???

[@FireStorm4056]

You were likely not traveling quickly enough for the aerodynamic differences (if any) to take effect. On a track your speeds will near 100 mph, where the discs can quickly shed heat between severe braking events. Remember that cooling largely does not happen during braking, but rather immediately afterwards. At 40-60 mph you were likely not in a speed regime where the aerodynamic differences would appear - this would be like testing downforce at low speeds - the tests would say it has no effect, when really you just need to travel more quickly. Also, measuring temps right after braking does not reflect aerodynamic cooling efficiency because all you've done is built up heat, but not allowed the system adequate time to evacuate the heat. Even on the downhill test, the final braking at the end to stop the vehicle could skew your results. Instead, you would need to somehow perform a braking event, run the wheels at high speed, and then stop them again (without using the brakes) to see how well they cooled after the first braking event.

[@xSiliconKnightx]

an IR thermo with data logger would have been a good choice. His methodology was pretty bad, really did not focus on the difference in the vane performance i.e. airflow at given rpm. Too bad he probably wont reply to your comment lol

[@MsSomeonenew]

A brake rotor makes absolutely no aerodynamic difference, unless you intend to mount them on your roof anyway...

[@FireStorm4056]

MsSomeonenew I don't think you understand what I meant by "aerodynamic cooling efficiency". The brakes don't noticeably affect the drag coefficient of the car (obviously) but the nature of the airflow through the brake rotor itself (through the center cooling slots) will affect the rate of cooling.

[@marco1173]

I have to agree. I believed the advantage isn't so much in how cool they stay during braking but in how quick they cool down after braking. As long as the car continues to travel at speed, of course.

[@poisonouspython1410]

Was looking for this comment. He formulated the worst kind of testing to expose any difference in an aerodynamic cooling design for brake rotors. Gee, let's get the brakes hot then test them immediately afterwards... oh look the lighter weight rotors are hotter. Who could've guessed. Makes me glad he stopped being an 'actual' engineer lol

[@blownss5924]

YOU have been working on you're car. I love it! a youtuber that doesnt pay someone else to do the dirty work.

[@EngineeringExplained]

Really just clever editing and makeup. ;)

[@blownss5924]

Well you're cosmetics person needs a raise. lol

[@DennisKarlsson]

You're=you are. You meant to write your.

[@JohnDoe-zg6fq]

+denka1337 You're*

[@DennisKarlsson]

No.

[@rreidnauer]

I'm not sure you are taking all things into consideration. Rotor temperature alone may not be the sole determining factor of performance. What if the rotors are carrying away heat from the pads more efficiently? Or, with the slotting allowing gas to escape may be offering additional friction, resulting in the higher temperatures, but increased braking as well. I'm not saying you're wrong. Just that, I'm not sure that you are right.

[@pdb4382]

Off-gassing isn't as much of an issue for current brake pad materials. However, the vents should aid in clearing dirt off the rotors, and should also shed water better than a solid rotor. I wonder if the slotting helps prevent rotor warp... Regardless, IMO you may be on to something.

[@Theredeemedchild2]

Slotted rotors are only for looks. The fastest cars in the world F1 cars, use solid rotors. Enough said.

[@cgpilk]

They are also open wheeled. Not saying you are wrong, but they are also nothing like a road car :)

[@cgpilk]

Or if a carbon ceramic brake for example generally won't even heat up to operating temperature on the street, so it may have anything from worse, same, or better stopping performance compared to the regular brakes on the street. Carbon ceramic brakes may even have worse cooling to try to get them up to temp quicker? Again I have no idea though.

[@garyindiana2127]

@@Theredeemedchild2 But rally cars use slotted, which experience more adverse conditions than tarmac, maybe they perform better in mud or dirt etc.

[@andysmith5940]

I love that you included the anomalous results and spent the time to explain them. Thanks!

[@AutoMiseng]

Actually the brake cooling can be maximized by the airflow. The slotted ( you called directional) rotor has a inverted hat design which helps cool faster. Your enginnering guess was right about the rotor weight (we called it heat mass) on stock rotor..the inverted hat design is better cooling design. Unfortunately the slot design does not helps as people think. This rather helps to remove debris and waters.. hope this helps

[@RRaucina]

slot only decreases mass which is not good. useless except as sales tool

[@GaryWold]

That was very informative. Let's not forget that in addition to better operating temps under extream conditions. The mass 2.2 lb. rotating mass reduction is good for gains in mpg, acceleration, & braking distances in a competitive situation. Love your videos!

[@TonyRule]

But in a road car, the best idea is to not get into the territory of 'extremes' in the first place.

[@faroles21]

I have no idea if someone said before but a key point is the fact the the pads needs to settle against the disc before test it.

[@enjoying_life49]

Yes, they need to be properly bedded, see my comment on 8-31-19.

[@rotorblade9508]

Yes, but I think the results would be similar. More mass has to have some impact on how they heat up and the directional vanes that seem to play a significant role (7-12% is not bad), are not efficient at low speeds like he drove. On a racetrack at 180kph the difference should become noticeable

[@mariangringo]

Rotor Blade interesting

[@mattweeks7142]

I always thought drilled and slotted rotors are for expelling gas from the pads. The slotted rotors might be pulling more temperature out of the pads themselves, causing the rotors to get hotter. Would be good to do a test on the pads for a comparison.

[@VCA.design]

The performance brakedisks are not designed to cool beter under load, but just after that. They cool faster till the next turn, that's the upgrade. And that's why they work better on a track then on a normal road. (at leased that what experienced) performance brakepads work better when they're hotter so the disks needs to be hot (hotter) under pressure. But i probably need to see the hole video.....

[@jordanpnb]

You are correct: From a materials stand point they would be designed to build heat quicker for better friction against the brake pads, but off braking to vent and cool quicker thanks to the vein design.

[@MontySpecTT]

I was going to say the same. They would cool off quicker then stock for the next stop n go situation.

[@mustardbiscuits5522]

You sound inteliigent but cant spell "Whole"

[@letsroll2463]

its an engineers curse, cant spell but will outdo you easily in logic and equations

[@Paul_Davies77]

Adam Myers And you can’t spell either! Inteliigent and cant- check your spelling first if you are going to criticise others ;-)

[@JoelGarcia-ml9jx]

Even if breaking performance is the same, less un-sprung mass is a worthy venture.

[@alienpoker]

@t1tacal I prefer a tinfoil hat so the aliens can’t tell what you’re thinking.

[@len-zeplin480]

@@alienpoker With an "HD" Antenna?

[@rotorblade9508]

Yes that’s is a positive thing however you don’t want the rotors to be too thin otherwise they will break. More mass means when you apply the brakes they stay cooler until you first stop so for road use they are more effective. Then after repeated breaking they will heat up. Racing rotors are not too large in diameter, but thicker and still not too heavy. However. They have air ducts with intensive cooling.

[@firstname7780]

inded. I am running 3D Strand woven carbon ceramics in the front, which saved 7.1 kg per rotor or 31 lbs for the front set, the steering increase with the angular momentum decrease, and 0.1-0.2 s 0-60 decrease. Also shorter braking distance but i have yet to measure that. Also, if discussing performance steel rotors lets talk something like Brembos with an aluminum hats which cools faster...

[@jtwu8931]

The increase in acceleration performance is mainly due the reduced weight of your wallet and bank accounts.

[@rotorblade9508]

Very nice and useful tests and analysis. I think the mass had a significant impact. The cooling for directional vanes is better but that when you are on a straight at 200kph which makes the difference. Less mass is better because of less unsprung weight but you need a minimum thickness otherwise they will crack. Racing rotors are two piece free floating and they are small in diameter unlike on supercars, but they are thick. However, with air ducts that blows a high flow of air in the middle, they can stay cool for tens of minutes of racing. The slots are also necessary for off-gassing. Racing pads which you cannot use on roads, are also used. If you want good brakes you want multi piston calipers, good pads, free floating discs not too big, and air ducts, racing fluid. Air ducts with good pads are still ok.

[@Nasonix2]

If it wasn't for youtube channels like this, we'd all be braindead from TV.

[@FlightSimXtreem]

People like him, makes people work correctly on their cars and knowing what they're doing. Instead of slapping on stuff and later find out it has gone wrong.

[@DENicholsAutoBravado]

@Brian Madsen hmmm.... There's something you don't know then. Used brakes, which aren't worn out of course, work better. So this gave them a leg up in the competition and they still lost. This all of course assumes your driving even needs better than stock style brakes.

[@chemicalspore]

I love TV *falls on floor in convulsions*

[@kismofer1]

@John D i just watch internet no more tv for me.....👍🏻👍🏻👍🏻

[@VeiLofCognition]

indeed

[@CarbsLVR]

The true scientist: "Okay so I did all this testing, but then I realized my assumptions were flawed, but that's okay because we still learned a little something in the end."

[@Aseutester]

rexseven93 Nailed it!

[@TimurIskhodzhanov]

Except a true scientist would do their homework / prior work research first :)

[@denbrice]

Jared Sherr 😎💩🌭😸🦊

[@Game-The-System]

Really interesting testing and video. Weight reduction & better heat dispersion during hard braking; seems like a win/win to me.

[@junechris]

You likely wont see much a difference at face value with 4 LBS of WR in regard to performance overall but I can see your point in that regard. It's still a slight improvement, of course with some aluminum anodized calipers, u might be at a more notable number, etc.

[@mrhelixx8944]

I search all over all the time... for everything about cars and part etc... and I always find my self back here on your channel... I just want to also say that you’re the best and amazing at what you do... and thank you!

[@brozach1394]

I think this should be taken as an example of how stock is better than aftermarket for daily driving.

[@mikhailg7914]

Try to flip it wrong way and take measure

[@drewshepard8002]

lone mazter EXACTLY

[@MatWilson2612]

Another variable would be if the new rotors had any form of coating on them? I'm sure getting down to the miniscule differences that it might make a tiny difference.

[@kabob21]

Brake rotors are a high-friction component. Any coating on the rotor doesn't last very long.

[@kellygnsd]

I do believe he is talking about the brake pad transfer of friction material to the rotor. New rotors or pads should always be bedded in and that process deposits a thin layer of brake material to the rotor.

[@mrobertsmr53]

He used old stock rotors and brand new outta the box aftermarket rotors. So the stock ones were more worn in and could take the heat better.

[@geworthomd]

Yup but decreased friction means decreased temperature and stopping distance. U get a B-

[@dt1mdlara]

1:33 According to this view, we can see the direction of the vents that confirms you actually mounted your rotors wrong. They probably labeled the box wrongly. The opening of the vents should point forward to scoop air for better cooling. I bet if you if you switch the rotors, you'll get better results. Still admire you doing all the time to do the tests. Thank you for sharing and God bless.

[@vcolinc]

The thumbnail looks like twin record decks!

[@MultiTerpen]

They look cool, of course they are cooler!!

[@TheSuburban15]

Kind of like, "Race cars are loud and fast, therefor loud exhaust makes your car faster."

[@AccountSpace]

We basically do this type of testing at my work but we embed TC s in the pad and rotors so we see live temps as we brake also sometimes pressure and vibration, but to get accurate data before every test we do a burnishing to make sure the pads mate well with the rotor

[@bqcaldwell99]

Ok, first, that’s probably one of the coolest vids I’ve seen in a while. I’ve been toying with the idea of switching my ‘07 F150 brake rotors to slotted, but I’ve come to the conclusion, and this was sealed by this video, that: 1. It’d really only be for looks 2. Even though I’m always on the road, I rarely have big loads or tow anything 3. I’ve seen videos and articles mentioning brake pad & rotor wear INCREASES with slotted/drilled. Thanks for this. Science rocks!

[@chefchutardo5215]

finally someone working with degrees celscius !

[@spaulagain]

Slotted rotors are not for slotted for cooling. They're slotted to allow for the gases and debris build up under heavy breaking to clear out and keep a clean pad/rotor contact patch. And the cooling ducting in the rotor is probably not going to be impactful on mellow road driving.

[@dtbrown1978]

Lol, it's funny that you're the only one who brought this up. I was watching this about was like wait a min. He needed to do this test with cross drilled which is designed for cooling.

[@campkira]

Having a air vent to the break would get better cooling with slotted rotors than a big break that make for bus....

[@nouvelhomme8990]

Yes. I thought everyone knew this. Weird video.

[@baotiny0608]

Would this make a difference? You used the old brake pads that were broken in and bedded to sit flush with those rotors. Putting new rotors but old pads could have a possibility to not use all the surface of the pad which would create hot spots.

[@envagyokzaz]

Old pad would be "broken in" to the new rotor by the time he got to the first test location.

[@DENicholsAutoBravado]

@@envagyokzaz yes I agree. It doesn't take much assuming the rotors aren't grooved. . . And they weren't as far as I can tell they weren't even slightly grooved.

[@DENicholsAutoBravado]

@@envagyokzaz plus, a new pad would be another variable.

[@jamesbrett5010]

I think the point of the slits on the braking surface of the rotor is to let hot gas out to allow the pads to keep pressure on the rotor. The small difference in rotor temp could not mean anything at all. I think you should have checked breaking distance rather than rotor temp. Your videos are awesome.

[@kstoneace]

I am amazed how much I learn from your channel. Thank you, your a great teacher and you have an amazing amount of knowledge.

[@Tommy.McLean]

but they're air cooled so shouldn't you brake then travel a little and see the difference in cooling between OE v. aftermarket? you would also think you'd need a specific brake pad with the directional rotors do increase the breaking and cooling but decreasing the coefficient of friction to run cooler.

[@detaildr]

Thomas Comptois I said the same thing but you beat me to it! But yes I absolutely agree, thank God someone else thought of it too.

[@mcspikesky]

Thomas Comptois the energy required to stop the car is the same if the speed is the sams, that energy goes into the rotors/braking system. keeping the pads the same means they hold the same energy.

[@Tommy.McLean]

the energy is the same I never questioned that. I'm just saying you change the coefficient of friction by changing materials and design. and the other point was rotor cooling is done by airflow dissipating the heat from the rotors and not when your stopped. granted great will still be radiated to the air while at rest but the main cooling effect is done while in motion

[@Tommy.McLean]

heat will be radiated

[@Tommy.McLean]

Artem Brayson I couldn't agree more

[@bw1235]

Looks like the new rotors aren't bedded in very much and don't have a great transfer layer. Since you said you changed pads, you've lost the opportunity to try again when you have a good layer on the new rotors. Until things are bedded in, you'll be seeing the results of a blend of friction modes.

[@TheBlackstealth]

bw1235 That will change stopping power because the frictional coefficient will be different but the kinetic energy that both rotors had to dissipate was the same because the speeds of the tests were consistent. This means the same amount of kinetic energy had to be turned into heat by both rotors. (well technically the slotted had less kinetic energy because they were slightly lighter so the car was like 2 kg lighter lol)

[@bw1235]

TheBlackStealth all true. But consider that the heat won't be conducted as well into the body of the rotor or the bulk of the pad. Akin to a heatsink interface with poor TIM.

[@MsSomeonenew]

I highly doubt that makes even a fraction of difference for cooling.

[@EngineeringExplained]

Drove around a decent amount on the new rotors before testing. Ultimately you're putting a certain amount of kinetic energy into the brakes as heat, depending on the car's mass and the speed you stop from, which are held nearly constant. Biggest variance will be my braking force, rather than how fresh/bedded in the rotors are.

[@joshtheking1772]

Im gonna have to disagree with you here. There may be some scientific reason but the real world is different from a lab or controlled environment. Its frictional energy. Sort of how a flat tappet camshaft wears to a flat tappet lifter. Once they have worn to each other they are mated to each other, thats why you SHOULD NOT change lifter location for each lifter when doing camshaft work.

[@sylvainlandreville3425]

Well... My own experience with a 2011 Dodge Grand Caravan. I used to go through only one Montreal winter and by the end of spring the discs were already warped. I switched to drilled and slotted discs and those lasted three winters before noticeably warping. Worth the difference in price. I also clean and relube every spring because the calcium really is bad on the calipers and guide pins.

[@Print2shoot]

Thank you for this comment. The 1 to 3 year change in warping time has me sold on the drilled/slotted rotors. Somehow I warped some crappy regular duralast and high end non drilled brembo rotors. Each lasted 11 months of daily driving. I can’t figure out how to get the guide pins out of the rubber boot so I never change them :( really want to live them up

[@billyhouse1943]

Once an engineer always an engineer...! Never say I was once an engineer....!

[@planewire2153]

Billy House well he means that he doesn’t work as an engineer anymore

[@kyrie4451]

Shut up, he has a girlfriend now.

[@soaringvulture]

Well, what is he now? A KZbin host? But his channel is "Engineering Explained". So I'd consider him to be a meta-engineer.

[@adamsinkie207]

Kyrie actually LoL

[@michaelstellitano2810]

Are you getting shorter stopping distance from the new rotors? That will get you hotter temps too.

[@fatkid8523]

Brakes for racing work at higher temps. When they are cold, they might not grab very well. Once warmed up they perform good, and can take much higher temps without brake fade.

[@ipullstuffapart]

Wouldn't it make sense that the amount of heat put into either rotor would be the same? Considering that the pre-brake speed is the same across tests, if shorter stopping distances were to put more energy into the rotors, that wouldn't really make any physical sense, as it's the same amount of energy to dissipate. Unless you're talking about the total amount of effective time of the rotors spinning to cool themselves, which could possibly provide a difference.

[@tricd0444]

ipullstuffapart I think that's what he's getting at, a shorter stopping distance in theory would have less cooling happening through ambient air dissapation than a long stopping distance. In practice, the impact of air dissapation while breaking is minimal compared to the air dissapation while off the brakes

[@WZW1982]

Stopping power is in the pads, hydraulics and tires.

[@williamwhizz6496]

Michael Stellitano , good point.

[@shaneebahera8566]

i think this test is abit flawed because brake cooling requires the rotors to be spinning to really work so if you stop the car with the brakes and then measure the temperature you are essentially measuring the brakes at their hottest without letting them cool down using the built in cooling. the only real way to test them in a safe way would be to jack up the car then speed up until the a predetermined speed then put the brakes on until the wheels stop spinning then speed up again for a given amount of time, and let the wheels coast to a stop then measure the temperature

[@mkloppers]

Cooling due to the directional or non-directional veins is still occurring during braking, and so heat is constantly being shucked away by the air even though braking is in progress. This is especially apparent in his downhill test, and the track testing. The cooling is not just occurring after the pads release. Overall, the directional rotors had an advantage when the temperature differentials were very high, and undoubtedly speeds were higher too. Combined with the fact that they are lighter, and still outperformed when pushed hard, gives them the win. His tests can be faulted for not pushing the brakes hard enough or high enough speeds.

[@iamasmurf1122]

The way its flawed is because he used the same brake pads , he should have used same brake pads for each rotor because brake pads on different rotors require bedding in to different rotors and that will create rotors to get hotter

[@bartley440]

I believe you are correct. I think the slots are to cool the rotor down after stopping when the car start moving again. Basically it only cools when the rotor is moving..not braking. It cools the rotor after braking not during!

[@kevinb7551]

I would say the slotted rotors shed heat faster and therfore absorb heat. like aluminum foil vs a steel pan the foil will heat quicker but also dissipate quicker. the brake rotors with slots is likely made to handle higher Temps, meaning it absorbs more heat breaks faster and cools faster.

[@johninmunich]

What was the stopping distance? Maybe the aftermarket rotors are actually performing better, overall. After all, the purpose of a disk isn't to stay cool. It's to stop. Higher temperature = higher friction = faster stops... (And, don't get me started about materials... Which ones warp faster?)

[@xXHokoriXGloryXx]

The stopping distance of the aftermarket rotors would not make much of a difference if it is not under heavy usage/load (like in a track). As the video mentions, the rotors cool better at much higher speeds and temperature. If you're really looking at stopping distance, the material used (e.g., ceramic) and tyres have more impact to stopping distance; or you could use a big brake kit which could skid a car a normal car. From personal experience, changing the brake pads to aftermarket (e.g., brembo or bendix) made a huge difference for me in terms of response time (how quick the brakes engages) rather than the rotors. Changing my tyres to performance type reduced my stopping distance.

[@johninmunich]

@@xXHokoriXGloryXx Agree. I have experience with Bendix pads (not Brembo though) and there was a noticeable difference. They wore better, too.

[@hiphop4x4]

101˚F garage "I used to be an engineer and i lived in a cubicle. You know i didnt have windows, but i did have air conditioning. But its way COOLER to work in a garage..." Nice pun lol

[@Jenuin]

awesome scientific video. I liked how you said your test didn’t quite account for the mass and therefore it wasn’t a fair comparison.

[@john_dee1431]

Been a while since your video but still want to say great work. It seems to reflect expectations for daily driving and I appreciated the downhill without engine braking part.

[@Chris-eo5zs]

In terms of your conclusion, it begs the question; are these rotors worthwhile for anyone unlikely to use their car in a racing scenario? There's also another issue. While the test was purely about the cooling efficiency, the key performance indicator of a brake rotor is its ability to decelerate the vehicle under varying conditions. Whilst temperature has a correlation with performance, longevity etc, it doesn't take into account differences in material. It may be that these performance rotors are hotter, but perhaps their design temperature is simply hotter given the specific chemical properties of the alloy they are constructed from. In other words, their peak performance temperature, may well be hotter than the stock rotors. Just throwing up ideas for consideration, happy to discuss.

[@TonyRule]

Yep. There could be a variation of the applicable specific heat given a slight difference in materials but it would be minimal. Thermal mass though is not insignificant and the fact that the temperatures read were achieved effectively with just static, or low flow, air cooling makes that a significant factor in favour of the heavier rotors, given the similar duty, as they would have heated less in the first place for that reason alone. Ironically, about the only thing NOT measured was the increased effectiveness of the directional vanes on temperature as this would have to be measured while moving, before a second brake application. That shows up in the test results of the other party who DID measure temperature in the environment they're intended to be used - fast flowing air. And just as you've suggested, the performance rotors may also be more resilient and dimensionally stable at higher temperatures and less likely to suffer from thermal stress.

[@isuguy82]

I love the beginning of this video. Especially the "I don't know how to play football, but I'm trying"

[@lPridel]

The aftermarket rotors were definitely doing thier work because to stop you have to change the kinetic into thermal energy so of course they would be hotter if they stopped faster. He didnt have the rotors spinning and measure temp while they are spinning to check how fast they cool.

[@gtavtheavengergunnerlegend3340]

lPridel yep

[@oldwortex5818]

If you watch the video then you will realize he did. He stated the cooling numbers in centigrade and that showed the slightly better cooling of a slotted rotors versus oem style. Bottom line is, just like we suspected all along, the difference is really minuscule. If you are so good, that you need that last bit of performance, put the performance rotors on, but otherwise you will be perfectly fine with the quality oem setup.

[@videomaniac108]

If the thermal energy produced is at the expense of the kinetic energy then how would stopping in a shorter distance result in higher temperatures? The change in kinetic energy would be the same, and hence the rise of the thermal energy(measured by the temperature) would also be the same.

[@stefanosstamatiadis740]

I love how you followed your thought path, resolving conflicting data along the way. A true engineer.

[@fredsterner5248]

I found your experiment very interesting. I spent over 35 years in the automotive parts business with new car dealerships, most of it with GM. I learned a few interesting things about parts over the years. New car manufacturers are required to test their new models extensively before release. Yes, I know that doesn't mean they hit the showrooms as works of perfection all the time. Problem is, in the USA there are no laws that require aftermarket manufacturers to test or approve anything that they sell. This is sad because they could make their part better than OEM (original equipment manufacture), about the same as OEM or their part can be junk. They are required to prove nothing because they line the politicians pockets. However, on brake parts, there is an approval designation, D3ea, that sets out testing standards for rotors, pads, etc. If they do the testing and pass, they can put D3ea approved on their product, and that is the standard the car manufacturers must meet. That means that the product meets the same fade and stopping specs as OEM or better. Without that designation, you have no idea whether their product is at least as good as OEM. That may not sound impressive, but an extra 20 feet to stop could be very deadly. GM"s Durastop line is D3ea approved and they make brake items for other cars such as Ford, Chrysler, etc. Hope this helps someone when purchasing brake pads and rotors, drums and shoes at your local autoparts store.

[@Ivan-ry7vm]

I think the direction of the slots matter. Can you test the directional discs installed in the two directions. Also for better comparison you might leave one wheel with aftermarket and the other with performance and run them together, but make sure that the brake lines are bleed. I agree on the cubical part, I am about to do the same, i even have the window :) Thank you :)

[@AL-31]

Thanks for using Celsius (:

[@qpSubZeroqp]

Alex Baker I agree with this statement

[@marksman712]

i mean he is an engineer, so a man of science essentially, at least on a basic level and that means conversing and being fluent in SI units. not silly imperial units :P

[@nestr2007]

ditto

[@kainhall]

a lot of science was, and is, done in imperial. im american, and know both systems very well...... imperial is MUCH better at some things.......like finding half of something... ya just double the bottom (or 2x to find double) half of 1/2 is 1/4......2x2=4 half of 7/8s is 7/16s.....8x2=16 now with SI....find half of 3.7945..... ya actually have to write it down or use a calculator.....(least for me) and at the end of the day...... 0c and 32f are the exact same thing....just expressed differently...

[@georgiohenderson5998]

kain hall the reason you think a lot of science is done in imperial is because you're American. I'm American, but i know most science is done in metric. Not all science is done in America, a majority of places use milliliters, centimeters, celsius, and so forth.

[@andrewwilkinson5220]

Thanks for doing the tests and showing the result. That’s about as good as you can test with basic equipment and not a super expensive ASTM certified test

[@GroHouse]

Cool video! .. but did you 'break -in' the new rotors?

[@ibrahimeltony4865]

Personally when I installed rotors like this. I only care about the stopping distance especially at the urban areas and sure at the highway. They did a great job really better than stock. The temperature doesn't mean so much to be honest with you. As long as it is doing the job.

[@mattbosch8893]

Temperature does play a different brake fade is caused by heat and when you get brake fade your stopping distance increases greatly

[@David_Saijen]

@@mattbosch8893 that's what slotted are for. Decrease brake fade

[@mattbosch8893]

@@David_Saijen never said the slots didn’t all I said is that temp does play a difference in braking

[@nicehashlogin9858]

what about stopping distance

[@darrenporsch]

How he doesn't message stopping distance I have no idea that's basically the main way you rate brakes

[@allen9845]

I think this proved that for normal road driving it doesn’t matter what kind of rotors you have but for racing they are beneficial. Great info thank you

[@froesesp]

It's not just temp, most importantly it's stopping distance.

[@TheSteveac]

You didn't give the rotors time to do what they were designed to do. You hit the brakes and measured the temperature with out letting the veins do their job. They don't work if they are not turning. Maybe do a brake check, but instead of stopping immediately. Get back to a speed of your choice and then use the e brake to stop you so you don't taint the temps. Just a thought. Love your vids. Keep it up.

[@steveprestek9608]

Slotted rotors are for gas release. Drilled are for cooling.

[@DENicholsAutoBravado]

Doesn't the release of gas more efficiently also let go of heat?

[@okramw1]

Wow! Cooling must be the end all of everything (as it relates to friction)? I'm curious how the pads that were used interacted with the different metallurgy of the different rotors & what the stopping distances were. I would like to see that graph, & then I might have a better picture of what's really going on.

[@joraforever9899]

only men who work all day to a car will understand the surprises of finding black spots on the face

[@magnavox4794]

Sometimes I'll be at work the next day and in the mirror on the way out of the bathroom realize the back of my arm is still grey.

[@Karza_357]

Accidentally touching your face with dirty gloves. Been there, done that.

[@ShawnJonesHellion]

JoraForever most hard laborers get that. Construction etc.

[@406_chevelle8]

I get more shocked when I just so happen to glance at my hands to see a trail of blood on there without a clue of what I hit. I laugh everytime haha.

[@eideticex]

More surprised when I don't get black spots on my face after working on a car.

[@billthompson9595]

Quailty and the tempering of that particular cast along with the type of vanes and the amount of space between those vanes is where the difference is I believe. Great tutorial!

[@AZDESERT2024]

Did you take into account the stopping distance differences between the two rotors ? I assume the slotted rotors may have stopped the car in a shorter distance - that may create more heat, but the directional cooling fins will cool it down quickly. I'll accept 13 degree higher temps if it stops the car even 1' sooner.

[@DrSwib]

If you can trip ABS on a set of brakes you're limited by tire grip not brake pads.

[@acroghan13]

I don't know if you released this but the rotors are actually on backwards, the vanes are designed to scope the air when in forward rotation, if he was to replace run his test with the rotated Round he would see a difference performance of the aftermarket rotors!! 😁

[@ionhunter]

Would had love to see the data with the directional rotors in revers rotation.

[@videomaniac108]

I recently replaced the stock one-piece straight-vaned Akebono rotors on my 370Z with a set of Akebono two-piece aluminum hat curved vane rotors from Z1 Motorsports. The front rotors are about 10 lbs lighter than stock, with the rears weighing about 5 lbs less. I also went with a set of G-LOC GS-1 street pads that have a coefficient of friction that is almost twice that of the stock Akebono pads with a much higher operating temperature range. The improvement in suspension dynamics, steering response, braking and acceleration was quite noticeable. With the forged magnesium monoblock wheels that I put on earlier that shaved about 9 lbs off of the unsprung rotational weight, I have taken a total of about 22 lbs from each of the front wheels and about 17 lbs from each of the rear wheels, including the lighter Michelin Pilot Sport 4S tires that replaced the OEM Bridgestone Potenza tires. There is also much less impact shock that is transmitted through the suspension and chassis when I drive over bumps, holes and irregularities on road surfaces. The dampers and springs are now able to more easily control the motion of the wheels over rough surfaces. Putting stiffer Hotchkis anti-roll bars on the front and back has also helped make the suspension more responsive.

[@mauricewrangler8554]

Great video and appreciate all the time, effort into these test which i assume it took a long time to collect and put together. Thanks

[@stevejcoop]

Brakes need to be at an optional working temperature, maybe the performance rotor heats up quickly to gain better braking, but at the same time not getting overly hot. Just a thought.

[@snwbm]

Optimal

[@TonyRule]

Your braking limit is your tyre grip, not the rotors.

[@neutrodyne]

I found this to be a good, and an interesting video. Thanks for taking the time in doing it. I have a couple of questions. What effect would the groves or holes in the rotors have on the brake pads? Would the groves in the rotors cause the brake pads to wear out faster? Would the metallurgy used in the rotors make a difference?

[@chuckschillingvideos]

No noticeable effect on the pads. Slots and drillings in rotors are staggered so they will essentially "cover" the width of a pad.

[@baxor]

As someone said in the comments, pads need to settle in and brake force cant be measured correctly by your foot half way to the floor. Also look at the surface on the original brake rotor and you will see them shine. The performance rotor is new and has still the crosshatch pattern which is a more rough finish to it. The brake pads will grab the rough finish on the rotor harder and therefore creating more friction and more heat

[@NotME535]

Could brake break-in affect the temperatures at all? The old rotors and pads were broken in, but the new rotors were not. Also, because it is hotter does not mean it is not cooling better, as i could be getting hotter because it was turning more kinetic energy into heat, making them hotter? I say this because it is a brand new parts vs an old one, it should work better, right?

[@TheBlackstealth]

João Mendes Because of the speed was consistent, the kinetic energy that was converted to heat is the same for both rotors

[@NotME535]

TheBlackStealth yes, but if you stop in 5 seconds or in 10 seconds (for example) it will make a diference

[@ikbendusan]

this is why live data acquisition would be better in this scenario than stopping and checking the temperature

[@ToxicityAssured]

The OP and commenters are missing something obvious. Multiple posters imply the brakes are converting the kinetic energy into heat. NOPE. You all even say the SPEED stays the same so KE stays the same. What is being turned into heat is potential energy PE. You're right though about the time heat relationship. Since the same amount of PE is converted into heat in the same time (because same speed) the test is fair. I just wanted to point out that KE was not being turned to heat, rather the PE. The engine put all that energy in the system raising the car to the crest of the hill.

[@aero5937]

Directional rotors = less mass ( gets hotter easily but gets cooler easily too ). For RACING, its better.

[@drjimjam1112]

I think you left out an important factor, you didn't measure stopping distance! A shorter stopping distance is going to yield a higher temperature. I think it would also be interesting to do the 3 hard stops, then drive say 5 minutes, roll to a stop then take the rotor temperature. What I'm looking for is, did the aftermarket rotors stop in a shorter distance, get hotter, then cool quicker. Remember, the function of a brake is to stop. The shorter the distance the better the rotor and pad. I don't care if an aftermarket rotor gets hotter than a stock rotor as long as it's stops shorter and stays straight. The stock rotors on my G37 warp and wobble like a b**** after they get worn a bit.

[@SpeedDaemon3]

He said consistent lap times. So the same braking distance. The point is they are useless for the street where we drive our beasts 99% of the time. And slotted rotors chew really fast trough brake pads compared to normal vented rotors.

[@SlikLizrd]

You say: "The function of a brake is to stop." That's very true, but REMEMBER : The brakes stop the WHEELS -- it's the TIRES that stop the vehicle !!

[@olivialambert4124]

Thats a pretty long video to conclude "systematic test errors, unreliable data". Still, nice to see the actual test results at the end.

[@dl6741]

Olivia, don't worry your pretty lil head over it.

[@djstringsmusic2994]

@@dl6741 she is right though you dingus

[@SpeCifiC0507]

@@dl6741 Do you like the taste of boot? Lick it more, ya dolt.

[@googleuser6440]

Wanna go on a date?

[@olivialambert4124]

@@googleuser6440 My dude, its the internet. I know people are getting a little desperate from being locked up for months but you can't date someone over the internet.

[@camerond8176]

So being brakes are designed to convert vehicle kinetic motion to heat, the aftermarket rotors started off cooler (dissipated more heat), finished off hotter (absorbed more heat from pads). The pads are the fixed object moving with the car, the rotors are the moving object moving with the tires/road (vehicle movement). The whole design of brakes means the pads create friction with the rotor creating heat, the rotor absorbs and dissipates this heat through the rotor and cooling fins. The whole point of the slots in the rotor are to vent gases under extreme braking when the pad/rotor surface gets so hot the pad begins to gas off, creating a layer between the pad and rotor and actually lifts the pad OFF the rotor reducing friction all together. These slots allow the gas to escape and restore friction and braking.

[@anthonytrujillo7971]

Alright 1st of all modern metallic and ceramic brake pads don't "off gas" under "extreme" braking. 2nd of all this video isn't about slots you dingus pay attention.

[@lancelefevre351]

Maybe the aftermarket rotors are better at conducting heat from the pads too. That's also seems to be really important. If the rotors are made from different alloys, I would think that would affect the heat transfer. Cooler pads would be better stopping as well. Just a thought. Might be worth a look.

[@RRaucina]

The alloy is called Chinesium

[@RandominityFTW]

tl;dw: Upgrades for the track aren't necessarily upgrades under usual driving conditions.

[@YeetxBoi]

You know some people wanting brake upgrades actually care about going fast safely on the road or track tho. If you upgrade your disposable rotors for looks that'd be pretty sad lol

[@williammcdorman6426]

Thank you, don't mess with standard equipment for normal driving.

[@ajsylvia9823]

You seem to be comparing brand new aftermarket vs your old brakes. The cross hatches you see on the face(not the slots but the break in cross hatching) actually causes more heat during break in due to the added friction from the hash marks. Your old rotors have worn those off. Therefore no added friction hense the heat differential. Break those in and do another test. My dollar goes towards the directional vented once the break in cross hatching is gone.

[@fermitupoupon1754]

Except that when I bought new brake rotors for my Renault Twingo, they came without any grooves in the brake surface. That is not to say you aren't right, just to point out that not all OEM brakes have that kind of pattern in them.

[@DENicholsAutoBravado]

I am a mechanic and I'd have to say all rotors have a pattern on them to help break the pads into them. I can't think of one exception, not that I paid attention every time, but when you're cleaning off the grease from the factory, which prevents rust while it sits, you notice the patterns on new rotors. Never perfectly smooth.

[@fermitupoupon1754]

Are you sure that's not just the pattern left by the mill that finished the surface after casting? I've seen those on just about every brake disc I've installed on my bikes or cars. But I wouldn't refer to those as some sort of break-in pattern.

[@raevennull]

He's not talking about the slotting, he's talking about the cross hatched pattern. Typical, you want to change pads at the same time as the rotors. There is some necessary initial wear that mates the components. I will typically hit my rotors with a flapper wheel when just changing pads. There is likely going to be additional friction during the break in period on top of the heat converted through stopping.

[@spencerphilippinedream3706]

i agree 100% with your analogy. actually 120% because your mind went to variables i didnt think of. but i would have tested them quite a bit differently. i always like to minimize variables and test the extremes when i am trying to understand an outcome. 1st, the idea of "vented" is that air is going to help to cool them. so i would test them being hot and cooling them instead of them being cold and heating them. so to get the most air, you have to get the most speed. so here is my solution to testing these. 1. put vented on one side, stock on the other, then switch for the second series of tests just to eliminate any variables related to each sides braking dominance. 2. push the brakes to failure (not on a hill, and not very fast either in case brake fade causes it to pull to one side) 3. measure how fast they cool while sitting still. this should give you a baseline. (and account for mass) 4. "reheat them", then travel at the "speed limit" (120mph if you can find one that high.....wink, wink) and coast to a stop (engine braking and emergency brake) measure them again. MASS in itself makes sense also. in a street car, most brake fade will occur on a hill (in my opinion), obviously not much braking happens going up the hill (brakes are cold), and down the other side (slower speed), greater brake mass would be a good thing, allowing more braking before failure. in a race car, brakes are never cold, brake mass only adds to rotating mass and counter productive as taking longer to heat up also means taking longer to cool. my opinion is that this would give the best results of how much cooling the vents do. by the way, i absolutely LOVE your channel, it is my "GO TO" for anything i dont quite understand about cars. another side note. your jokes at the beginning were hilarious. KEEP UP THE GOOD WORK

[@ahmedbajric5390]

I think that's because the directional rotors are cooling faster(brakes are only cooling when driving).When you were measuring at the first test,you were staying and measuring and that's why the directional rotors weren't colder.And in the second test you were in move and thats why they were colder(they were in the move/better cooling)

[@magincap70]

The stock rotors were vented as well. They just weren't slotted. Less mass heats up faster but holds heat less than a heavier rotor that takes longer to heat up and holds onto that heat better than the lighter one. You also need to consider what materials went into making the rotor. Not all steel is created equal. More often than not the aftermarket is really full of junk and Oem manufacturers produce a much better product.

[@Tj1056]

that is if you choose a cheap aftermarket rotor then it is probably junk metal, but most aftermarket rotors use much more pure quality metals. Like for example a lot of stock rotors are made of cast iron with a slight mix of metals while quality aftermarket ones use more pure metals with reinforced carbon-carbon or ceramic matrix composites and other things to make the metal stronger and less prone to cracking and heat warping and such.

[@theblubus]

@4:23 I was mindlessly watching and thought "OH NO UNDERSTEER he's gonna wre...." ...oh wait right.

[@B3MMi]

Exactly :D

[@x-man5056]

That front rotor is NOT on the correct side. It is a right side rotor. Mine all had stickers on them, they go on so that the beginning of the slot at the inner part of the rotor leads the outer end of the slot as the wheel is rolling fwd, opposite of the way that particular one is installed. The way you have it, the heat would be driven toward the center of the rotor not the outside per design intent. I would be interested in your logic if you disagree but I am certain I have mine installed the way the factory intended. Mine are drilled also but doubt that makes any difference in preferred direction of rotation.

[@fatslapper123]

I noticed the same thing... I would think you would want the hot gases thrown away from the hub....

[@azurewang]

@1:38 you can see the inner part rotates at opposite direction of outer slots. I think he's right.

[@thomasbradley7844]

X-Man your rite lol only an engineer

[@omgitzsteg]

You're wrong

[@OrnumCR]

Thank you for this and great to see combined temps in both Fahrenheit and Celsius. Well done that man!

[@JusstyteN]

Did you account for rotor to pad breaking in? I think the most fait test would be buy new pads, and new rotors. Put stock on one side and these on the other.

[@Thumper68]

JusstyteN that’s a bad test one side would be grabbing different then other side screwing the results

[@billyb7561]

@@Thumper68 Agreed, glad there is still hope for common sense on the internet.

[@Thumper68]

billy b seems like I spend all day trying to spread it and it’s not catching on lol!

[@mrsleep0000]

One thing I've learned from modding Japanese cars...the engineers know what they are doing, there's very few things you can do that will actually improve them.

[@FaZeMandTaZeM]

Lol there’s a lot, manufacturers keep it cheap bro

[@theroyalcrownedtiger2946]

It's even better with european sports car and hyper cars. These cars have everything built for racing. The european engineers know what they are doing. Bugatti. McLaren. Lamborghini. Ferrari. Porsche. Mercedes Benz. BMW.

[@extremegenes6761]

Dude where do you live? That area always seems so beautiful for driving.

[@sungalupe]

he lives in oregon i think i remember that he has a vid where he shows what he does everyday if hes not making vids ✌

[@terryreese663]

Best part of test started at 10:04 where tester had used them on a track where the constant use could show real results of braking over time. This is where directional will show its merits.

[@bwdz75]

As a "former engineer" you should think that curved vanes dissipate heat while turning so they will cool off much faster in between corners not while coming to a complete stop and standing. Their purpose it to flow air out while spinning much like a flat blade fan vs a curved one so you would need to stop from lets say 60 to 20 mph several times and then recheck.

[@bjw8586]

Were the after market rotors broke in, normally brakes have a brake in period. And if they weren't broke in with in they're recommended milage, they wouldn't have the grove marked out in the pads and rotor, which would help with stopping and cooling.

[@edwardslavov2935]

So basically these rotors are useless if you don't drive the car on track. Thanks, I guess I'll stick with the cheap regular ones.

[@TheBenjammin]

Not necessarily, he only tested heat not performance.

[@theclamhammer4447]

Heat is not the sole performing factor. Carbon set ups not only run hotter but won’t function until hot. Yes, different material but there are other factors and potential scenarios. For instance one could suggest the rotors are hotter because they soak heat from the brake pads in turn cooling the pads. Maybe this isn’t the case but you’d need further and expanded testing to included the pads. He did mention the rotors do cool a tad faster. Another possibility is the slotted rotors physically promote more friction than the OEMs. This means they may stop faster but create more much more heat doing so vs the OEMs. With all that said..... even if they had an advantage, which personally I doubt they do, the benefits on a street car are negligible. My ZR1 has carbon brakes and that sounds nice and fancy until you have to replace them all while constantly reminding yourself that you just drive this car on the street so it’s a waste at a certain point regardless.

[@TheHannukahZombie]

@@muskokamike127 Not true, some pads need heat in them to work properly. Basically he's another youtuber that made a couple videos and now people take his word as gospel. This was a poorly done video because he's not doing the correct testing. Again.

[@TheHannukahZombie]

@@muskokamike127 Then the point of doing this test was moot. You aren't going to put on performance rotors and not performance pads. There's no reason to do this test other than to test a performance setup, which requires better pads that do require heat to start working properly. You guys are just moving the goalposts . We aren't talking about the vast majority, those of you here that don't want to admit you're wrong are just making things up to justify your irrelevant nonsense. Hot brakes DO stop as well as cold ones when you're comparing OEM brakes to performance brakes. You want cold braking performance for a street application to a certain extent, but rotors like these are meant for street AND some track time so you don't want Corolla pads on there. Honestly, I don't understand why you people open your mouth.

[@AdamDiM1978]

This is SO TRUE For EVERYTHING People do to their cars.. spoiler's, ground kits, lowering, coil-overs... so on.. If your not Driving the car fast enough, and hitting turns hard enough they do NOTHING.. and most people dont. they might try and push 140- 160 mph in a car but not for long.. so it's all pointless unless u go to a track.. It's all For LOOKS.. thats it

[@stergioser]

The problem was you're compare the honda quality standards vs aftermarket! Do it on a poor quality car & you will see big differences. You are doing very good job! 👍