Do Performance Brake Rotors Have Better Cooling?

Do Directional Brake Rotors Prevent Brake Fade?
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Do directional vaned brake rotors provide better brake cooling? In this video I test new brake rotors on my Honda S2000 to find out. I only changed out the front brake rotors, everything else is exactly the same (same brake pads front and rear, same brake rotors in the rear).
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[@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

[@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?

[@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.

[@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

[@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

[@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.

[@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!

[@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.

[@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

[@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.

[@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.

[@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?

[@andysmith5940]

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

[@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.

[@GeoffCostanza]

I'm glad you went into your methodology and independent testing results. I was wondering about the variables, like braking duration and time between tests/measurements, until you explained it.

[@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.

[@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.

[@mkloppers]

Thanks for addressing the mass difference, and the difference between your tests and higher-temp track testing.

[@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]

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.

[@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? 😉

[@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.

[@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!

[@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???

[@-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.

[@gekisoscion]

@@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]

@@gekisoscion 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.

[@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.

[@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

[@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.

[@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.

[@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.

[@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

[@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

[@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 😎💩🌭😸🦊

[@OrnumCR]

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

[@jeffdodd4276]

Thanks for a reasoned explanation of the pro and cons of slotted rotors.

[@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.

[@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.

[@sonidoa.c.g3884]

I really appreciate all you time and effort to just try to educate people here, thank you very much for your work. My best regards

[@staypositive4358]

I really like those hydraulic lifts. I want to get a set when I get my own house with a garage. I know they are a bit expensive but for someone who does a lot (or all) of their car maintenance it would be a great tool to have making jobs much easier. If I recall correctly, they also flatten on the floor so you can leave them underneath the car so they are out of the way.

[@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.

[@nvrdwn3140]

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]

@@nvrdwn3140 But rally cars use slotted, which experience more adverse conditions than tarmac, maybe they perform better in mud or dirt etc.

[@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

[@WalterPavlikII]

Very interesting video. (I just stumbled upon this) I think when you hit the mass question you sort of redeemed the tests. Lower weight at the corners helps with braking and handling. 1 kilo may not seem like a lot, but every little bit of unsprung weight helps. (I'm sure other folks have pointed that out, I've not read the entire 3,296 comments before mine. ;) ) That said, thanks for taking the time to do the tests. I LOVED the road you used for the downhill test. I'm a little jealous of you having that great curvy road to drive on a regular. (I'm NOT envious of the crazy heat though!)

[@patrickphippspa584]

Thanks buddy. Been watching you a long time now!

[@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-

[@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

[@haseebzeeshan6987]

Got what i was looking for, great job. Thanks for the video.

[@charles1379]

great assessment on the heating properties of rotors. thank you.

[@GroHouse]

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

[@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

[@jonathandough7409]

Bro. This is one of my fav channels 🙃🖤

[@johnbernard1854]

Great Job. Thank you for providing us with great information. In my opinion you are making a true contribution to humanity.

[@brozach1394]

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

[@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.

[@kevinolsen4948]

Thank you for this video! Helps me make decicions on my future purchases. I think your assumptions are correct about test not being in a high enough tempature range for the products to really show how well they handle stress and heat. I think they got hotter because obviously lighter rotors will get hotter quicker but also alows quicker cool downs with air flow and over all better weight reduction. When things start getting supper hot is when things start warping. Thats my concern to the point of replacment. If and when you feel like doing another video id like to see you push these to the limits on a track for like 25 min each! Thanks for your efforts and for sharing this info honestly!

[@troytruong8246]

kevin olsen drilled n slotted brakes are always better. I use them for a long time. Big difference.

[@craigdecolumbian2688]

Thanks for your testing , this will help me make a better decision on my next purchase.

[@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

[@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.

[@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!

[@hotrodray6802]

Always wondered about rotors. Thanks. You needed a gtech g meter for consistent braking rate. Also using the same old pads on new rotors and not broken in, requires more foot pressure/ more hear/ to get the same stopping g force and stopping distance.

[@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.

[@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 ;-)

[@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.

[@Cmensailing]

Great magnetic thermocouple! I need one! Also check cooling in air! More surface = quicker cooling! Also test at the same time left stock right aftermarket with a person in passenger seat with same weight as you in straight line! OK you sort of did!

[@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 :)

[@joachimkazmaier]

I'd say, that either you need to make the comparison with brand new stock vs. brand new aftermarket rotors, or break the aftermarket rotors in first, and compare with broken-in stock rotors, then do your measurements. Once the machining marks are worn off, the rotors will be significantly cooler.

[@Thomas-rt1de]

Now, test which stops better. I found slotted were better for shorter stopping distance. Let's see what your test conclude. And, btw, love your channel! Thank you.

[@aerovaportrail1392]

Always great stuff. Thank you for you time.

[@ionhunter]

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

[@mikhailg7914]

Try to flip it wrong way and take measure

[@drewshepard8002]

lone mazter EXACTLY

[@fxworld7012]

I put slotted & drilled rotors on all 4 wheels, my thought was slotted for the brake gases & the drilled holes for the cooling.. I have gone to school & been in the automotive business for over 45 years but am open to any input always.. Like you channel by the way..

[@vitor000000]

Hello Jason! I believe the aftermarket brakes are developed for clean the brake pads, avoiding vitrification on the brake pads!

[@triniscorp]

Sorry for the late comment but as far as I know the slots/holes in rotors are not for cooling. They are there to let hot gases escape from between the rotor and pad to prevent the "hydroplaning" effect on the pads. Sort of like running slicks in the rain, the water will cause the tires to float essentially causing lower running temps but if you cut groves in the tire the water can escape which will result in a warmer tire. And the secondary reason is for weight loss in a larger rotor. The larger a rotor is the further out from the center you can put the caliper creating a greater breaking torque but you add rotational mass so then you still them to counter the mass effect. But I could be wrong

[@geworthomd]

Nope, sorry. All this hot gas stuff is marketing bs. This is thermal build up due to friction. Cooling then comes from the wind. The next time u hear about hot gases in a metal friction experiment think hyperbole and farts. Those little holes and slots allow for the passage of circulating air to interact with the metal. If they worked the way you might think then we would have them on train wheels. Unfortunately, no. Heat soak and cooling are two different experiments

[@Plexico41522]

@@geworthomd the hot gases thing is really only a issue during wet conditions when water can splash on the rotors and pads but the video isnt even about whats on the otside its about the internal vains of the rotor

[@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.

[@angleradam1011]

Great video the topic is something I have considered often. I have a thought not meant as criticism. I don't think I care how hot they get because I don't replace rotors because the ran hotter than I prefer but I do replace them when the warp. Maybe several sets of similar vehicles driving under similar conditions to see if the aftermarket resist warping longer. Also, determine if the pads last longer or the rotors last enough longer to justify the additional cost.

[@mjrami]

Thanks for the time and experiences

[@vcolinc]

The thumbnail looks like twin record decks!

[@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.

[@jeeploggernz2289]

Excellent test bro

[@stefanosstamatiadis740]

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

[@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.

[@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.

[@alexanderoh1847]

Thanks very much for the deep dive in your own flawed assumptions. Super valuable to see that.

[@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.

[@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

[@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.

[@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.

[@tuneuptony3679]

Thanks for the information. I was planning to buy performance brake kit for my truck. I think i will stay with the stock.

[@isuguy82]

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

[@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

[@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

[@thewholls7176]

Good video I have to admit I always thought and had been taught those slots are not about cooling Those slots are intended to facilitate the escape of combustion gases and brake dust particles from the interface between the brake pad and the disk to facilitate a better brake pad “bite” and allow the brakes to work better and therefore the discs are hotter Basically the pads are allowed to bite harder without an inversion layer or cushion of gases and brake pad dust as the brakes are applied the pad material is essentially cooking in what is almost slow combustion Those bye products need to be removed and that’s what the slots do........ i’m happy to stand corrected Cooling boils down to the design of the ventilated section in the middle of the desk combined with the metallurgy being used

[@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."

[@NobleInsights]

keep it up bro...nice

[@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

[@Mytwistedvoices]

I would have used a data logging arduino. Measure the temp rise and fall while driving. I have done that with model airplane motors. Surprisingly I measured motor temp, ambient temp and battery temp at the same time. found out the motor would heat up on decent, when the power was at the minimum (less prop wash to cool the motor). Excel showed the line graphs.

[@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

[@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.

[@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

[@Tsxtasy1]

Would love to see you redo this test at a track!