Thru - Axle and QR analysed. Stiffer? Hmm.

Shout out to Waynos Fotos for inspiring me to make this video today.

[@nut-r6660]

I like your enthusiasm for investigating cycling technology and the use of first principles. I own a company that needed to design and qualify (to ISO Std) a QR interface so I am well versed in these interfaces and the forces tested for design approval. I agree that these parts shouldn't be called axles, as they are solely retainers. Based on my experience, the Thru Axle style interfaces do not solely rely on friction to prevent the hubs sliding relative to the dropouts. A quick friction calc would show that there is not enough resultant friction to prevent the hub sliding into contact with the bottom surface of the Thru Axle under mid to high loads. At this point the Thru Axle will be loaded in plain shear. The friction force at the hub interface only really needs to resist axial twisting against bearing forces (which are negligible) and cornering forces, hence why they have low torque figures compared to their thread capacity. The big vertical hits (from jumps or potholes etc) will overpower the clamping friction force created by the TA and simply load it in vertical shear. QR retainers have a greater factor of safety compared to TAs as they have a less safe open dropout design and as such have huge clamping loads to compensate. But the clamping loads are not created from the thread geometry, they are created from the lever and its pull ratio. From memory, Industry standards requires QRs to prevent wheel pullout by around a 200kgf force. This is a huge force! QRs also have hi tensile stainless steel male and female threads to cope with this high loading. Personally, I wouldn't recommend going beyond the TAs torque spec based on QR data as the clamping requirements are completely different and may jeopardise the TAs threads. This is my second alternative opinion on your videos and I am not the type of person to troll videos lol. I think that on all but the basic parts there is usually more going on than meets the eye. Cheers

[@nc3826]

Thank you for your salient 'common sense based' input.... And proving the old adage that, 'A little knowledge is a dangerous thing'... The different retention characteristics between TA and QR, makes it an apples versus oranges comparison. And secondarily the cross-sectional dimensions of a TA skewer, allows it to 'easily' serve alternative purposes, such as an attachment point for a bicycle trailer, which is not possible with a QR skewer. Lastly it's not trolling when you're making relevant counterpoints. Have a nice day.

[@jamesdirect]

Nice comments. I have a feeling that the wider the thru axle the more capable it is at taking axial loads. This does keep the bike stiffer in the wheel and probably let's the wheel perform at its best too.

[@kswsquared]

"Dude, why's it called thru-axle?" "It goes through the axle of the bike." "So it kinda like skewers the axle?" "Yeah pretty much..."

[@andrewbarton1538]

I think you are leaving a lot on the table - does a Thru axle make your wheel stiffer - No I agree- wheel stiffness predominantly comes from lacing pattern, hub flange width and diameter, spokes, rim design, and some inner hub-bearing design as you pointed out. But what you have left out is that a thru axle is more used as a frame structure than a wheel structure. Where the wheels attach to a frame is a open area that was traditionally not supported and relied on the hub to make it stiff relying on bearing interface - tolerances ect. Many parts working together... therefore a weak spot. The thru axle becomes an extension of the frame as one part - no bearings just one part to secure the drop outs together. This stiffness in the frame from a rider perspective can feel like the wheel is stiffer because it is not flexing under load. your steering tracks better, the back of the bike feels planted. An easy test is to take an old QR fork with a wheel and hold the wheel between your legs and turn the bars - see how everything flexes .. its shocking how much fork legs flex- do the same with a similar fork but thru axle and you will find it flexes much less. Does a Thru Axle make your wheel stiffer? no - but it does make your frame stiffer allowing you to harness more or your wheel stiffness that was always there. YES

[@willo7979]

the interesting part of marketing is, while they're telling you a 'good news', underneath the rosy garden they are actually trying to clear their shit. Thru Axle is never a predominant factor to achieve stiffness. Thru Axle is important for saving life. But not thru the Thru Axle itself, but the importance comes from fork end with closed loops (no more dropouts) so that your wheel still hang on to fork to the least when your wheel is trying to escape under serious disc-braking or fork twisting. Now then we can talk about stiffness. i'm 100% with you, that 'wheel stiffness' is provided by hub, from bearing setup, to hub, to lacing, to rim and then to tyre. Thru Axle has very minimum contribution to wheel stiffness. In reality, Thru Axle is a camouflage to a long existing problem: disc rubs and unwanted friction loss which is critical for road race and professional cyclists. putting a disc brake fork (for Thru Axle) and a rim brake fork (with dropouts) side by side, it is not exaggerating to say the fork end on disc brake fork is at least double the thickness of the later. The fork itself has to be beefed up for a significant stiffness improvement, that simply can't be achieved by a larger pipe without thicker fork end. In addition, the beefed up portion on a forks is concentrated at one third lower length till disc caliper mount. Still, that's as much as fork manufacturer can do, latest shimano flagship disc brake claimed to provide wider caliper opening (they claimed it is for quick wheel change yes that is very believable). all in all, i'll consider Thru Axle for safety. rest are just complimentary.

[@kevinwells1660]

It is my belief that disc brakes must have 12,15 or 20mm thru axles in order to get proper structure stiffness for disc brakes. Loads of cheaper bikes still come with open dropout QR. With heavy braking the axle can be pulled from its seat regardless of how hard you go on the QR lever.

[@willo7979]

@@kevinwells1660 walmart bike does not fulfil requirement as mountain bike, although they look like one.

[@kevinwells1660]

@@willo7979 some of the "leading brands" still sell open dropout MTB shaped bicycles, road bikes also.

[@willo7979]

@@kevinwells1660 hmm... ok Let’s demand them to admit their fault, refund or replace shall we?

[@elorz007]

2.2 hundred kilos, also known as 220 kilos haha. Sticking with your chosen unit like a good engineer.

[@PeakTorque]

Stubborn twat!

[@BenitoAndito]

PT makes me the stiffest of any KZbin bike engineer. Source: Hambini's recent Grindr survey.

[@Iowahurler82]

I just watched that same video last night as well.

[@davidmarshall2399]

Apparently he packs a big wrench

[@Hambini]

PMSL

[@dafj5618]

@@Hambini shhhhh Varah

[@LaurentiusTriarius]

In conclusion a bigger axle isn't always stiffer. That's 3 years of intensive research on cornhub... Here you go, some have to make sacrifices.

[@hermittranslator]

I like TA over QR because I think it does a much better job at holding the disc brake interface in place, so you get much less brake pad/rotor rubbing and scratching, especially when cornering.

[@MarkWarnePhotography]

I have never noticed any issue when cornering. The only advantage I can see with TA is when reinstalling that it’s bang on each time with alignment

[@whssy]

Talked about this with Cy from Cotic a few years back when they were considering thru axles for their next hardtails. His take was along the lines of "most people who buy our frames are using hubs with stiff axles so it's a non-issue". Only real benefits are slightly better disc brake caliper alignment stability and safety (as in the wheel can't fall out). Thru axle rear hubs brought smaller bearings with them so reduced durability.

[@p0t4toePotato]

i found that the hub options for 141mm qr are really limited though, so you are forced to use through axles if you want better hubs, for mountain bikes at least

[@PeakTorque]

Cotic. Engineers 👍

[@RC-fp1tl]

135qr and 141qr hub options are extremely limited, unless you want to drop $500 for a rear hub. That, knurled end caps messing up the dropouts, and brake misalignment are the only issues with 135

[@thomasjousse2427]

Genuinely love all these myths deconstructions, it truly helps in deciding what to buy/use and sort out all the bullshit. I'm kind of a torque maniac on my bike, so each and every bolt is torqued to spec, with my M12 "axles" at 11Nm; it's good to get a bit of confirmation on your part.

[@Laundry_Hamper]

Thru-axles make a huge difference in resistance to twist. If you've ever ridden a mountain bike with a ~150mm+ QR fork, you absolutely feel the "noodliness" that journos go on about. The extra axial surface from a "thru-axle" makes a difference there...and similarly on rear-sus MTBs, you used see lots of designs where you'd have a four-bar linkage with two disconnected parallel members at the shock which could easily counterrotate, or a train of a million side-loaded bearings to create an esoteric shock curve - there were (and I think still are?) lots of situations where the big 20mm thru-axle formed a proper component of the structure of the frame itself. On a road bike with proper rear triangles, that factor's pretty moot, but a twist-resisting thru-axle fork is still a good idea. I've a Merlin Inferno, which is a weird Chinesium frame with great geometry, and its thru-axle fork actually has a rubber-bunged hole drilled for a rim brake. You'd have to have a custom hub machined, but think of the sheer stance you could get on the spokes with a full-width pair of flanges on a thru-axle!

[@MsMihalko]

Exactly my feelings. Author of video, in all respect to his work, unfortunately analyzed incorrect situation around hub, should around the fork. But the bike designers just wanted to match clamping force of QR with TA. They implemented TA to stiffen fork

[@karl8805]

@@MsMihalko and rear end also..but yes your right...

[@jimbo4203]

My new specialized e bike came with thru axles and boost spacing front and back ! Super stiff and rides great

[@karl8805]

@@jimbo4203 exactly, this giys far cleverer than i am, but sometimes you look into something so much that you find fault whwn fault simply isnt there Manufacturers spent millions changing to bolt through, they wouldnt have done all the R&D, redesigned everything, bought new machines to make these things it wasnt making their bikes better..simple fact I mean technology gets better, F1 cars dont use steel brakes anymore

[@markwells8798]

When's ths last time you rode trails on your road bike? And then put a 150mm thru axle fork on it and rode the same trail and said yeah that's a way stiffer fork!😂

[@neal9151]

🤯 Really informative. I wish reviewers knew what they were talking about rather than repeating myths and half-truths. Keep up the great videos!

[@julmeissonnier]

The problem is that with both an Engineering Degree and a reasonable ability to write meaningful sentences with semi correct spelling and grammar, you can get a much higher paying job elsewhere...

[@pavel_zak]

Very interesting. Now if you excuse me, I'll be on my way to tighten some axles.

[@theadventurebiker]

7:16 - people mislead by bike industry B.S.???? NO WAY!!! That NEVERRR happens! Thanks so much for publishing this very informative video. 👍

[@tsiturbotsi]

Great job explaining and illustrating how this all works. Kind of amazing that a lot of people don't understand how the hubs themself are designed to take the load and the thru-axles just clamp.

[@JeffCowan]

"I pack a big wrench" ... no need to brag! LOL

[@GreatEgretAdventure]

😂

[@edmundas919]

On my old MTB in the front I have 20mm through axle (RockShox Maxle) and bearings (6804) directly touches the axle. Front wheel also have 15mm and QR adapters and those adapters just press in the bearing from the sides. And the rear wheel is 12mm through axle like in your drawing. Regarding sheer forces on MTB suspension forks usually one leg has spring (metal/air) and other leg has damper and both of them are connected with the thin arch which may flex on rough terrain. And in case of inverted suspension forks axle is the only thing that connects both fork legs.

[@zzzwillzzz]

i think you missed the forest for the trees. isn’t the issue more of the interface of the hub and dropout?

[@retardno002]

I believe he says the end cap is the interface of the hub in the dropout, and it makes sense, QR couldn't exist otherwise.

[@NigelMarston]

Another amazingly informative video - one which I have sent to a number of people who I failed to convince that the skewers offered no part in the mechanical loading (other than clamping). I still prefer thru "axles" though. They're a little more fiddly for thieves, but mainly because they make it impossible to misalign a wheel. I've seen QR clamped wheels offset numerous times where the owners have not seated the actual axle properly in the dropout. You can't do this with a thru shaft. And whilst a 5mm QR might be able to offer more clamping force, any thru shaft can provide sufficient amount of clamping.

[@yourrightiamwrong9643]

Really, there is no "Tech" in Bike, just stuff got adopted from other industrial applications, that have been there for like 30 years plus.

[@gregknipe8772]

the only true modern tech in bikes now seems to be BS from sales reps. and marketeers. propelled by KZbin 'influencers' skilled @ changing tires.

[@carlosflanders518]

It's all about enabling better power transfer. Standard sales nonsense for shoes, pedals, cranks, bbs, bars, hubs, spokes, rims, saddles ...

[@yourrightiamwrong9643]

@@carlosflanders518 and weight, saving 2kg on equipment while the rider could easy lose a good 10kg (talking about myself here).

[@imperialspy3457]

@@yourrightiamwrong9643 what if you already weigh 55kg? Much lower and it will be even harder to find clothes.

[@yourrightiamwrong9643]

@@imperialspy3457 thats why i am limitting this argument to people like myself. Generally if theres no (healthy) room for improvement in weight or power or position on the bike, then go for dura ace, 1000g wheelset and ee brakes and so on. But we all know that is mostly not the case.

[@alexandersukhanov2901]

So it doesn't affect wheel stiffness, what about frame and fork stiffness? Axle becomes a structural element of the fork or rear triangle and resists twisting forces. Compare Manitou Circus dropouts, or modern Fox 38 with open dropouts for QR wheels

[@willo7979]

you'd just pointed it out, left and right sides of forkends became a rigid piece linking by this rod therefore the forks is stiffer.

[@willo7979]

when fork is stiffer, left fork twists less upon disc braking, thus caliper will have less chances to cause disc warp perhaps.

[@jimmit77]

Thank you. I was hoping someone would point this out.

[@justpedal65]

I think you guys are missing his point. He focuses on the need for clamping tightness throughout the vid for a reason... because the "spot" where the endcap or axle nut (older assemblies) is pressed up against the dropout is the actual theoretical "position" were the integrity of the assembly (wheel mounted by either QR or TA) interacts with the whole system for stiffness (ie fork and frame)...NOT the larger dia of the TA to the outside of that. In the caveats near the end, he points out the TA does provide "extra bracing" against asymmetrical brake loads. So basically what this means is: With dropout torsion, the larger diameter of the TA does help a small amount TO THE OUTSIDE of the clamping surfaces of the fork or frame drop outs...which are usually only 6 to 25 mm in thickness...so again, a very small amount aiding stiffness. The majority of the stiffness, however, is produced at and to the INSIDE of these points.

[@zombiewoof5257]

@@justpedal65 I think you're underestimating the effect of the diameter of the axle (not the clamping bolt) and it's contribution to the stiffness of the whole wheel mounting construction. Motorcycle axles used to be 12 - 15mm in the old days, now they're more like 25mm, this absolutely increased the stiffnes of the construction. Increasing the diameter increases the angular momentum the construction can resist, so the clamping force might not need to be so high as Peak Torque claims. In any case it's bad advice to tell people to use longer tools than advised by the manufacturer, it might cause very expensive damage to your bike.

[@chrisw.1090]

Thanks!! I was a little worried that my QR mountain bike with added mid-drive motor might be not as safe as a thru axle, but this video clears that up!

[@eayzgaj]

I don't think that's case closed. Just done a back of envelope calc and it showed that the thru axle or QR is seeing a higher axial load than the pre tensions you were calculating with your bolt spreadsheet. Once you overcome the pretension the QR will stretch more than the thru axle so in this case the thru axle will make the wheel feel stiffer. With the QR the hub axle end caps will pull away from the inner faces of the dropouts more and allow the wheel to twist.

[@timsmart8225]

Surely thru axles are about combatting the huge amount of twist torque that discs exert on the interface between the QR/TA and the dropouts? This can pull the axle out of the open end of the dropout, so that is closed and stiffened with thru axels.

[@LawrenceButcher]

One place I can see a benefit to a large diameter through axle is in the more extreme MTB application, where the axle is also clamped by pinch bolts on the drop out, which should (I think) increase the rigidity of the fork assembly. Also, the latest axle design on RS forks combines a 15mm axle with a cam action QR lever which should help increase clamping load. Awesome video though, thanks.

[@user-du6op6qx5s]

you should have more views. Finally someone that says everything as they trully are.I myself have found that actually the old threaded axle provide the most clamping force and actually adds rigidity to the frame. Well done.

[@wangdangdoodie]

.....but there is still potential for movement because the dropout is open on a QR system.

[@patthewoodboy]

when its described as a "thru axle" its just saying its going thru the axle , not an axle.

[@willo7979]

QR skewer goes through the axle too.

[@patthewoodboy]

@@willo7979 yep but they have been called quick release to explain what they do.

[@julmeissonnier]

@@patthewoodboy So through axles should be called "slow release" then! We have definitely seen a lot of that in road races since they were adopted ;)

[@patricklivingstone6076]

I was looking for this comment. Exactly as you say, it's not an axle, it a thing that goes thru the axle and the dropouts

[@dangerous8333]

@@willo7979 Right, but that already had a name.

[@colinvanwijk5731]

Thru axle: it is a part that goes through the axle... Misleading name? Not an axle itself but is does describes what the part does... (or am I just being smart now....)

[@doesntmatter7774]

If that's what the name means, then a quick release is also a through axle. But since a quick releases aren't called "through axles", that must not be what the name means.

[@pankow2893]

My word...GREAT to hear someone use the crucial lexicon "load path" with facility. My first professional days on the job (1976) I heard a bearded, grizzled vet use that term in dismissing poorly thought out structural reviews.

[@smallhatshatethetruth7933]

Thanks for the education. First was under the impression that the axle provided load bearing and then I upgraded from a QR specific wheel to a 12mm wheel with end caps and realised that was bunk. I was finding that this set up was loosening up by itself over time but I guess I wasn't applying enough clamping force. Was worried I would break it or mess it up if I put too much load on the QR skewer

[@andredegraaf1643]

Hallelujah! Finally, an engineering analysis not a marketing pitch. Nicely done.

[@biglytremendous5191]

My brother went to a bike park a few months back. He had a blast ripping his side knobs off his tyres. As he went back home he realized, that his draw bolt came lose. He replaced it afterwards. With a lose QR he probably (almost certainly) would have lost his wheel, and would have been seriously injured. The main benefit to through axles is that you can not lose them so easily and the disc-caliper alignment is really good.

[@bjma654651651]

Weren’t through axles introduced in response to disc brakes pulling wheels out of dropouts? Once you change from a dropout to a hole in the fork end, then the utility of the skewer-type QR is lost: you can’t just drop the wheel out. The through axle simplifies the whole arrangement by making the “skewer” just a single piece of “pipe”.

[@denisdrc5836]

Peak Torque, thanks for your content! Having seen lots of your videos debunking marketing claims, I've got a question: what would be your perfect bike from engineering point of view, if it were up to you to design such? Could you make a video on that, please?

[@SJworne]

Cracking idea!

[@johnkemp3592]

+1 to this!

[@davidmarshall2399]

Perfect for what, whom, when, and at what cost? Engineering is balancing those questions (and many others) for specific outcomes. there's no one right answer to any engineering problem.

[@sepg5084]

@@davidmarshall2399 "your perfect bike" means what would be PT's dream bike for himself.

[@davidmarshall2399]

@@sepg5084 for what tho? He's shown in his vids he's interested in road, TT and MTB. I'm just trying to highlight the issue with the words 'perfect' and 'engineering' in the same sentence.

[@georgetapley776]

A number of years ago I was repairing a carbon mtb frame for one of the local jr racers. He had crashed on it and broken a seat stay clean through. When he brought the bike to me with the wheel installed 12X48 Boost the two parts of the seat stay did not line up. When I removed the thru-axle and wheel the two parts lined up perfectly. That told me that the actual thru-axle system had enough beef to it for it to correct any mis-alignment in the drop outs not being parallel to each other. So just another way for the manufacturers to hide their poor quality control. Overall you are so correct in a larger bolt needing a higher amount of torque to achieve the same clamping force. As well as the axle not being part of the load path. Thank you. I have been preaching all of this for a while now.

[@FranciscoRubioB]

Oh Hambini was totally right... at least in regards to the engineering analysis skills. 1. ThruAxle is not about the clamping screw but about the whole system. It doesn’t matter if you put a QR-Clamp in it is still thruAxle and it is still stiffer than the previous design. 2. Because the TA design is stiffer you don’t need as much clamping force as in QR. 3. As previously mentioned, what is stiffer is not the screw but the whole system. As an example of a fork this means that the whole fork-wheel assembly is stiffer. You need this as soon as you have the asymmetrical loads of the disc brakes acting on one of the fork legs. If you’d have a skinny fork as in QR with disc brakes you would have the feeling, every time you brake hard, that the bike is trying to turn left and you need to correct to the right. Because of the lower forces and superior structure of the back wheel you have normally a smaller diameter on the TA in the back. In other words what you say in the video is useless and (partially) wrong. Nice try though.

[@willo7979]

1. Theoretically Thru Axle pushes bearings to go larger in inner diameter thus may geometrically have better lateral wheel stiffness, but that amount is debatable. 2. I doubt the improvement in stiffness (via TA, if there is any) is enough to compensate potential reduction in clamping force (as told by PT, it is still recommended by mfgr to maintain tightening torque to achieve the same theoretical clamping force) 3. Whether it's a TA or not a TA, your fork length stays the same, and it still flexes if there is no stiffness improvement on the fork itself by design. If fork still flexes, your disc caliper still rubs the disc because caliper is mounted on the flexing fork while disc is on the hub. Perhaps there is a reason company like shimano makes claim that their latest road disc caliper's piston stays wider (they claim this helps in wheel change, which i think it is another bs). again 3. Do you really think that rear wheel do not need 15mm and those businesses are happy at 12mm? have you thought of how 10t or 11T sprocket feels? think again. of course i agree with you that rear triangle is less of a problem for lateral flex.

[@cd0u50c9]

Love the complete lack of fluff and BS in these videos. Breath of fresh air!

[@georglinde3910]

Great video! One comment on the cross section of the rear hub: this is NOT like DT designed their 240. In my opinion it is for a 240 like so: the axial clamping force there is transfered from (right to left): - right endcap - inner race of 1st freehub bearing - spacer ring between the freehub bearings - inner race of 2nd freehub bearing - another spacer ring inner race of right hub bearing - right shoulder of hub axle (so no play there) - left shoulder of hub axle - inner race of left hub bearing - left endcap. There is a gap between the endcaps and the face sides of the hub axle.

[@_S13_]

Dont mistake clamping force for stiffness of the fork. Anyway, i love my fox floating axles. Very precise wheel alignment, same clamping force as a QR, and fast removal (approx 5secs). On an MTB they make a lot of sense!

[@jonathanguu3141]

The term stiffness comparison of thru vs qr based on clamping force comparison is selective analysis. The diameter of thru axel hubs vs diameter of qr hub caps against the fork is more relevant. Though contact surfaces of hub cap against mating parts is far more significant for fork, versus the rear dropout. Hence caad qr rear.

[@karl8805]

My super X dale is qr rear, no where near as stiff as my road bike which is bolt through....

[@PeakTorque]

Friction does not depend on surface area. F=mu.R You can look it up!

[@albullit]

Who mentioned friction? Surface area. Torque Caps, for example. Bracing angles? And why are you calling them thru-axles when it’s a bolt through, let’s not perpetuate a myth.

[@karl8805]

@Pablo Morales qr bikes always have paint chipping off the dropouts... bolt through doesnt.... Amount of times ive had to removed deformed paint from qr dropouts...never had to with BT

[@cularu1]

​@Pablo Morales My QR bikes does have some carbon or metal eaten in the dropouts. not to the point of failure but it has some because there's high pressure in this points. The pressure is more distributed in the case of a thru-axle.

[@fieldlab4]

I thought, like a motorcycle axle, the idea with a bike through-axel is that it's a very tight fit in the dropouts. Such a close tolerance that no slippage is possible and therefore much less clamping force is necessary. The idea being that it's an axel system that does not rely exclusively on friction resulting from high clamping force to maintain axel position in the dropouts and wheel position. If that's not how they work, guess what kind of modification I would make first?

[@Wacoal34d]

Analysis from first principles, at least first engineering principles, always provides clarity, big up to you Peak Torque.

[@sufyansaleem9771]

Maybe I missed something, In the QR case the end cap actually sits in the drop out, but with the Thru Axle the hub doesn't actually sit in the dropout, so the radial loads are taken up by the axle by in the QR case they are taken up the friction of the endcap against the inside of the dropout and bit of the end cap that sticks into the dropout.

[@mikeymike65]

Yes, you did miss the point being made. When you lower the forks onto your through axle wheel, they sit snugly on “something”. That “something” is equivalent to the end cap on the QR case. It’s what transmits the loads. The through “axle” is only doing the same clamping job a QR does

[@Robert-rh9op]

I can't speak for all bikes, but on my Giant with thru-axles, the hub sits on ledges on the inside of the frame. In other words, a wheel will sit in its place in a thru-axle bike without the thru-axle, just a QR wheel would.

[@sufyansaleem9771]

@@Robert-rh9op hugh that's weird on my mtb there is no such ledge, on my road bike fork there is those.

[@82vitt]

A good observation. On my road bike with disc brakes, the fork has a semi-circular lip on each of the drop outs that embrace the end caps from the top, while the fork on my mountain bike has a semi-circular recess machined on the inside of each drop out which does the same thing. I doubt it is structural though, and is there only for the user convenience, so as to position the hub and hold it in the right place for the insertion of the thru-axle.

[@sufyansaleem9771]

@@82vitt Yeah My road bike has them front and rear, the MTB only has them on the front. Its a rock shox fork that is designed to take regular hubs or power tourque hubs so the cut out is way too big for regular hubs. The wheel only rides on the axel no other support.

[@tristan3763]

Peak Torque, can you make another America's Cup video please? Some good engineering analysis on the Mozzy Sails channel but keen to see another Peak Torque video on their aero packages now the boats have all added new fairings and shrouds.

[@gustavorincon1640]

I think you misinterpreted the fact that a thru axle provides less clamping force: that means it's stiffer so less force is required, as some have said, it's an extension of the frame and adds structural integrity, keep in mind that it sits flush inside the real axle, with no play, and it remains locked with it.

[@alexmorgan3435]

I'm old school and still use Shimano QR as I believe they give the highest clamping pressures. Always thought thru axles were a con unless they could be tightened enough. Need to carry a FO Snap-On/Park torque wrench in your saddle bag just in case you need to get the wheel out and then refit out on a ride.

[@EricaMTB]

The through axle is designed to make the fork or frame stiffer, regardless of the hub. Greater fork or frame stiffness is transferred to the hub for better tracking of the wheel. The small axle end area of a qr combined with narrow dropouts and flexible qr allows the hub/fork to flex in relation to one another. It's not about vertical movement of the mating surface, it's about flexibility. Apply a side load to a rim and measure deflection.

[@antoniop1968]

Less a minute and half and hearing thru axle is no more solid than QR, that’s all I needed to hear. Glad I’m old skool using QR.

[@rsmiii]

As an american who is stuck with american english I keep hoping to hear you tell us "The claim is X, which is actually bollocks when you look at it." Such a perfect word for debunking myths as you do here.

[@daydreaming_aristocrat]

Thanks for that video, made me understand the engineering of hubs and "axles"

[@in4merATP]

Sure would be nice to see a compression load cell set up to show what kind of clamping forces are actually generated, across TA and QR. Cams are most definitely not all made the same; please consider an appendix with some demonstration, pls? It'd be really nice to have a table of clamping force to brand/model of QR skewer. Those of us with alu endplates would be most appreciative. Also, I've a QR disc frame yet to build and would love to be armed with the facts.

[@richardggeorge]

I agree. My Shimano QR's are so much better than my Novatec and SRAM branded ones which sometimes ended up slipping on the dropouts (road riding)

[@rmc9189]

One advantage of 'through axles' is your wheel doesn't fall off if they come loose. Much prefer the allen bolt type than qr bolts. They may not add stiffness to the interface between the hub and the frame but they seem to improve frame and fork stiffness especially on inverted forks and Horst link frames. I wouldn't want to go back to 9mm qr on an mtb.

[@nickw6175]

now oddly enough in October I had a flat stopped to change the tube and found that my inner axel had sheared so when I withdrew the thru axle the entire rear wheel assembly fell apart in effect it was only the pressure of the thru axle on the frame that was keeping it all together, a close call.

[@keithb4158]

Great review. Somebody who knows how stuff works. The marketing department would hate you. Well done.

[@cularu1]

There'rs been QR Axles with disc brakes! Thru-axles wasn't invented because of discbrakes!

[@dalailambda9420]

Yes, but with QRs you can have the wheel pull itself out of the drop-outs, if you're unlucky and lock up the brakes (at least on the front), so I'd still say Thru-axles are probably the better choice in that respect.

[@GregTheGuitarist]

@@dalailambda9420 unless it's a shitty dropout it's very unlikely to happen. Most of the dropouts for disc brakes with qr have little flanges around the area where the skewer cap goes. Simply said: thats not just flat thing with cutout on the bottom. So even of it's not tight enough the wheel cannot be pulled out. Most of the cases - those flanges are too small (shitty fork/ frame) or non existing (even worse manufacturer or some improper conversion to disc brakes) - or (worst case) somebody didn't check if the skewer are clamped properly.

[@FightFilms]

@@dalailambda9420 Nope, not if you install it right and tight. It's going nowhere. Not with lawyer lips on the fork. It's simply impossible.

[@grimp53]

The main problem with QRs not clamping wheels strongly enough, is that so many people don't know how to tighten them properly, in the way they were meant to.

[@user-du6op6qx5s]

@@dalailambda9420 have you ever seen a qr wheel pop off place cause of disk brakes? I my self haven't seen this, like ever.

[@krider7296]

Great video! Thank you for taking the time to show how the hubs are constructed and the way the forces / loads are distributed. Why do people jump on the cycling industry's marketing bandwagon. I wish people would put more thought into what they buy and why. If road cyclists in the pro peloton had a choice and were not forced to showcase the cycling industry's latest revenue generating gimmicks they would be primarily riding on rim brake bikes.

[@domestique3954]

Absolutely! 🤙

[@frankjaucot6846]

Very interesting, in essence then the advantages of TA are more precise alignment and MAYBE some increased frame stiffness due to the precision of the interface which does not rely solely on the clamping force to keep the axle in position. If you forget to tighten your QR things can be pretty dire but even a slightly under tensioned TA will still keep your wheel from falling out.

[@gweflj]

Great as always but... I think it’s more likely that manufacturers will spec a larger OD endcap/frame interface with a 12mm through axle V’s a 5mm QR. This has to be where the main stiffness benefits come from. See the Rockshox Torque Caps. I think the reason QR disappeared was disc brakes putting more braking force through the wheel which could be a disaster if the user didn’t sufficiently tighten a QR. It’s more noticeable when thru-axles are loose before the wheel falls out!

[@MrGoodaches]

Thank you for a thoughtful and useful analysis. Your point is taken re stiffness of hub but my thought has been similar to other commenters that the TAs improved geometric stiffness of the fork and also but to a lesser degree the rear triangle. I would be very interested in seeing you apply the same orderly presentation format to fork and frame behaviors with the various "axle" types. I stumbled upon this vid on my quest to replace front and rear hubs on the matched pair of hard tail MTBs that my wife and I have. The MTB market has become so segmented that I don't see anything new that is adequate across the versatile range of riding we do. Certainly see new bikes superior at specific things but we need adequate at everything. Anyhow, all else was spec'd well except the cone bearing hubs. We don't need high end hubs but we do need upgrade to sealed cartridge bearings. Some of our riding encounters contamination that too easily bypasses seals of a cone system. Even when new these hubs had the sounds and friction as if the bearings were river pebbles. If anyone has a recommendation for a cartridge bearing hub set that isn't priced like aircraft parts I'd be very appreciative for the input. Bike is 100 front and 135 rear QR. Rims are 32 hole. Brake disks are 6 bolt. Cassette is 9 speed Shimano/SRAM. Sorry for moving off topic but the community attracted to this vid includes the people I think would have good recommendations.

[@There_N_back_Again]

Spot on... QR and/or through axle supports the clamping load... They don't actually take sheer loading. It's the hub that actually takes the sheering load. Thru axles is a gimmick

[@GuyonaMoose]

Through axle doesn’t make the wheel/hub stiffer. It makes the fork stiffer. The chassis flexes less therefore you track better. Axles would bend constantly if they took weight on a mtb it’s only job is to clamp the wheel to the bike. Very good and scientific overview!

[@ms.karihart2983]

I’m new to MTB and thought throw axles was the answer, after hearing your examples make sense Thank you sir

[@tomeklubomir]

I really like watching your videos, you know what you’re talking about 👍. 2 pointers for future experiment/video to mention.1st - the lever in thru axle is quite small to put a lot of torque through it (you mention 4NM), but are the threads in the fork blade really strong enough to take more than 10-15 NM. Perhaps the small lever provided is protecting the threads from being over-tightened by the user and hence shredding the threads and the need to replace the whole fork. Could you investigate what load would the treads take without damage... 2nd - it’s a fact that many cyclists do their quick release skewers to different tension (some - too loose and some - too tight, that you struggle to even undo the lever) and this affects preload on bearings/end caps/fork etc. differently, but also affects brake pad clearance in a hydraulic disc brakes. I converted my TRP Spyre mechanical disc brakes to BR RS785 hydraulics and I can notice that the pad clearance in hydraulic disc brakes is much much smaller with less adjustability compared to old setup. It’s therefore very sensitive to QR skewer preload tension and repeatability of the same tension... Hope this makes sense, keep up the good work 👍

[@kosskrit]

I know it is an old comment. The common misunderstanding of function of QR leads people to false conclusion that amount of tension put in skewer somehow affect alignment of disc brakes. QR is there only to put enough preload to hold the wheel in droupouts by friction, the alignment is done by geometry of fork/frame itslef. Bike manufacturers fucked up the concept and made the surface of vertical faces of droupouts and/or hubs serrated. They've probably thought it is a good way to add extra friction into equation. However, this cause misalignment everytime you dismount and mount your wheel because you are unable to hit the previous configuration of dents.

[@davidburgess741]

I see through axles primarily as locating the disk precisely so that the pads don't rub. It would be rubbish if every wheel install required a caliper adjustment. I didn't know about the DT 350. They must have been desperate to save weight at the bearing's expense.

[@Primoz.r]

Even with a 12 mm through axle you can insert the wheel at an angle and get disc rub. So the solution is simple and applies both to QRs and thru axles - before tightening the axle, set the bike on the ground to fully engage the dropouts. That way you get very simple repeatability and the same wheel location every time. Which affects not just the (disc) brakes (it will affect rim brakes as well of course, they are just a bit more quiet when rubbing), but your shifting too.

[@user-du6op6qx5s]

​@@Primoz.r exactly. i never understood how exactly people don't have the repeatability of brake location with qr. you just sit the wheel to the ground tyhe rear axle sits on the dropouts and you tighten. this rubbing problem didn't seem to exist befora thru axles came around, so i consider this rubbing old issue, just a marketing hype to sell the new type of product

[@moo4rich]

I have 4 bikes with QR and disc brakes and no issues in locating the wheel for rub free brakes. 2 have front through axles and have had both rattle loose, I have to force tgem so tight I'll need a rock as a hammer to get them loose if I have a puncture that tge tubeless and plugs don't sort. My FS Epic is QR front but has big diameter end caps and this is stiffer than my rigid MTB with a front through axle. Most small developments are just to get you to spend on a new bike.

[@firemedic5365]

@@moo4rich I'm no engineer. That's why I kept my opinion to myself. But I kept thinking throughout this discussion why one would not simply place larger diameter end-caps on the quick release skewers. Does that make sense in any way? Were told, don't you dare use quick release frames with disk brakes. Doesn't seem to hold water, that argument.

[@detmer87]

I have a flush (no lever) 12mm Thru axle on my Cannondale that has a 9 ~ 13.5Nm rating. I used a torque wrench and torqued it down to 11Nm.

[@hgh96]

congratulations, You have the same clamping force as me on my shitty QR's

[@detmer87]

@OmegaMan I have strong hands, anything up to 20Nm is doable with a short allen key. It will leave a nice red tattoo on your handpalm for sure ;) And you can always lean down with your shoe on the allen key...

[@JulianIrwinX]

Thanks for the analysis. Repeatable wheel location is the only reason I need to only use Thru axle frames.

[@robinrai4973]

I quite like the Suntour quick lock thing, it's essentially a QR Skewer in the form of a thru axle

[@jonnoMoto]

It took me almost a decade to jump on the thru axle bandwagon in MTB. Going from a dirt jump qr fork (massive crown) to enduro thru axle forks I could not tell the difference. I'm thinking what people were actually feeling were wheel and fork design changes.

[@karl8805]

Ive had 2 sets of the same wheels 1 was qr one was bolt through BT was far more rigid Forks were the same (qr version amd BT version) BT feels noticeably superior, if you cant tell the difference there is something wrong.... Next people will be saying running a 23mm tire and a 28mm tire feel the same

[@willo7979]

@@karl8805 While thinking it's the wheel that makes the diff. Have you ever thought that that the fork end on your BT fork is forming a close loop (compared to a QR fork) and that should be given some credit too, if not completely?

[@karl8805]

@@willo7979 my point wasnt the wheels, it was the BT set up as a whole was far better

[@kyleslater5245]

The stiffness that I found with a 12mm bolt vs the qr was actually in rear triangle flex. It’s harder to twist the rear triangle then previously. That was the stiffness I was after. Basically you are calculating just the side to side load on the axle not the whole bike. While I agree you are right when only keeping the axle/wheel loads in mind overall frame the smaller diameter doesn’t seem to provide as much. I don’t know I felt it did more in the department of changing how the rear triangle behaved because the larger diameter prevented frame flex to a degree. The same goes for the forks as well. The “thru axle” is more for connecting the legs then making the tire stiffer.

[@recyclespinning9839]

I tend to agree with the theory that a thru axle , and the bracing needed now on the front fork due to needing a stronger fork mount for the force placed on that area by the braking calipers in that area , has now removed the natural springing in the front fork which really has a lot to do with ride comfort. My vintage Raleigh Super Course had an amazing ride. I gave it away and now recently bought a vintage Raleigh Super Course MK ll with beautiful curved fork. I am servicing all the hubs, crank, head set and looking forward to the ride. The bike industry is just to geared towards changing things right now.

[@zerge83]

Thank you. I always had this suspicion, but never had the knowledge to prove it. Never felt any difference to qr, in fact when I was a bike messenger I had really low atc fork, the 22mm tires the bike came with just barely cleared at the top, soon I had to change tires and I could only get 23s, so I had to lift up the bike a bit before clamping down the qr, so the axle wasn't all the way in the dropout. And I rode like that for months thru cobble stones, endless potholes, speedbumps, jumping up and down curbs, drafting behind buses, doing 90-100 km a day and it didn't move once.

[@karl8805]

Most normal people wouldnt be able to tell the difference....i can Same with these idiots that say 105 feels the same as ultegra when it clearly doesnt

[@joshportelli]

You sir are my hero. Subscribed! I have designed automotive beam axles and use joint calculators alot! Just getting more into bikes and was hearing alot of misinformation on thru axles vs QR. I agree with you that they are just a bolt to provide clamp load on the joint and not part of the load path.

[@lawrencesingleton2153]

Thru-axle. Goes through the axle. QR axle, is the hollow axle which takes a QR skewer. Nobody said either of these things were axles? Also as long as the flexural stiffness of the thru-axle is greater than a steel QR axle, the rear triangle will be more rotationally stiff. Fact. This will mean that when you are putting out a lot of power you will get less twisting and you will also improve the stiffness to asymetric braking forces, meaning the stays don't need to take that part of the load. The wheel won't be stiffer, but again I don't think anyone has been saying that the wheel itself would be any stiffer?

[@jeanbout7868]

Journalists need to sit through a solid mechanics class fml

[@kc3718]

they aren't journalists, they are sales people. Journalists are a rare breed in the last 30 years or so. Sales people two a penny.

[@jeanbout7868]

@@kc3718 I was being generous with the job description 😂

[@kc3718]

Started reading mtb and Cycling weekly back in the early 90's the only journalist amongst all the 'sales people' I can actually recall is Chris Juden technical chap at the ctc ( degree from Cambridge in engineering ) and various of the mainly advertisement magazines. I think they get rid of him because he was a journalist and not a paid bullshit merchant. The modern incarnation of the magazine is GCN and that's tripe too. My favourite pseudo journalists came up with phrases like '' the springy steel frame saves up energy and unleashes you forward as you attack the summit'' Should have written fantasy !

[@tjgraham3597]

@@kc3718 So i do agree with the overall disdain for marketing in the cycling industry, as with all business they do need customers that can help pay the bills for those of us "tech geeks" that ride because we love the outdoors, and the engineering of the machine. So if "the springy steel frame saves up energy and unleashes you forward" sales marketing gets them out there to buy and maybe even ride the really well damped tubeset made of wonderfully dense Reynolds air hardened 953 chromalloy, then I am ok with that. Now what I can't handle is some bullshit marketing that straight up lies about features like internal cable routing that helps you with less maintenance on you new bike. In no way does internally routed cables every save you time or money with your maintenance regiment of any bike. Journalist being sales people isn't all bad but i do hates me some salespeople that have clue technically of what they are selling. The bicycle shops I have worked in and or have managed have always made it a rule if you're going to sale bike you need to have a basic mechanical knowledge of bicycle so we make them service wright once a week under a Sr mechanic. So that is our "Journalists solid mechanics class" @JeanBout

[@rcg9573]

k c - agreed. They are marketing people pretending to be journalists. One of the bigger lies of most “reviewer/pretend bike journalists” is when they claim they were not paid to review a bike or product. But what they don’t say is that if they were to give out a negative review on a product they would likely never be sent another product to review by that manufacturer ever again. So they have an inherent bias to cheerlead every product they receive. And when they do rarely give a middling type review they virtually always do it with a manufacturer whom they really do not review often or care whether that manufacturer never sends them another product for review again.

[@n0ch91c3s]

I'd contend that the actual axle on the DT 350 front is a combination of the center sleeve, bearing inner races, and end caps. All are held in position by surface friction and the thru axle still doesn't necessarily contact the bearing or all other parts.

[@Gyikhuszar88]

That's the point.

[@n0ch91c3s]

@@Gyikhuszar88 video suggests that this design places shear loads on the thru axle. My description suggests it does not.

[@Gyikhuszar88]

@@n0ch91c3s I agree with you. However this sounds a little bit strange. Something should wear the loads come from the front wheel, I think that friction between the edges of the spacers - bearing inner races - inner spacer - sleeve would be not enough.

[@johndef5075]

My 2013 Devinci has a rear through axle but its just a longer skewer. Same diameter as qr.

[@simoncossettini9680]

great video - I am trying to get my head around a simple problem of using 9mm QR wheels and adapting them to 15mm 100mm forks - if the skewers/thru axles 9mm or 15mm are friction not load bearing they in theory with the right adapter washer/flange be tightened down on the external edge of the fork and clamped so they don't move.

[@owltune5496]

I really love smart people. It is how we all learn and discover and advance. Although in this case I think some cyclists think of stiffness in the fork differently . I understand the vertical force. We get reminded with every bump in the road. I think when some cyclists refer to stiffness it is in the idea of rotational forces. Feeling the fork twist? That wiggle wabble? Sure I understand with load and force and directions but as much as forks and or dropouts skewers, axles and such, how can the twisting feel be improved and will a axle improve strength or resistance in that direction. Should we steer more towards hub upgrade? Especially for the swarm of adventurers strapping loads to the front of forks. Thank you.

[@steveflor9942]

True story: I once bought titanium skewers for a Masi Gran Criterium. Was hilarious.... Could feel the rear wheel twist in the dropouts when pedaling hard while going over bumps. An exemplar of what NOT to do.

[@jamieroberts6345]

This video completely missed the frame/fork interface and how a fork with a 10-20mm overlap of the axle will be stiffer than compressing a slotted dropout between the at head and the axle. There is a clever caveat at the end “ not stiff in the way most people think they are” so the actual subject of thru-axles benefits can be ignored

[@aaronperelmuter8433]

What exactly do you mean when you say a “10-20mm overlap of the axle”? 🤔Exactly which part of the fork is different from currently and what is overlapping what and where? Also, the only person who’s ignoring the benefits of TAs is you. 🤨This video is NOT about the benefits of said axles, it’s whether a TA is stiffer than a qr, which as we’ve seen, it isn’t, in the vast majority of cases. 😳The only thing which has been completely missed is your understanding of what this video is about. 😱It definitely didn’t miss out on anything.🤓

[@szurketaltos2693]

So what would be the ideal solution? Here's my suggestion: 5mm solid thru axle. You get the increased clamping force and repeatability of locating the rotor, with a more easily manufacturable skewer - people could even use their old skewers. Suspect easier to align the frame during manufacturing. Would love to see a follow up also talking about fork stiffness -- the fact that lefty forks exist suggests to me that the thru axle doesn't do much here.

[@aaronperelmuter8433]

What would be the point of using a qr as a TA? 🤔And why would anyone ever want to use their ancient qr skewers on a brand-new bike? 😂 That makes no sense whatsoever, as it’s the frame and forks which determines if a TA is used. 🤪Moreover, I very much doubt a 5mm TA will have sufficient ability to locate the wheel and disc as there’s just too much play in the threads themselves when they’re such a small diameter.😱

[@julmeissonnier]

Great material. I always wondered why hub companies do not use the TA as the real axle and put bigger bearings (12mm ID instead of 15mm ID) as the hub axle and TA seem redundant and I did not know DT actually had one hub designed like that. But you are right about the fact that doing it that way you need a very sloppy fit to be able to remove the wheels in the field... Now, I fear that we may see plastic bushings like in the Shimano BB making their way into hubs (or hopefully the Mavic experience with plastic bushings in freehubs was painful enough...)

[@grahamm2015]

Ah the power of placebo. Excellent update and clear description thanks.

[@YoureSoVane]

Next do Flat Mount vs Post Mount comparison. Would like to know how much the mount style affects torque and alignment under load

[@charliewhelan9488]

Isn't the main selling point aero gains.

[@ballerman3430]

I really appreciate your effort in your videos I have got a question. Where do you geht the CAD Models? Do you measure them and build them yourself? Or do you get them from the Web? Best regards Ballermän

[@4headgaming448]

How do quick release and thru axles compare to lateral loading of the fork? I seemed to always get disc rub with an older QR fork I had, but with a thru-axle it's less. Not a good comparison by any means, but I'm still curious of your thoughts on this. Thanks for the content!

[@hannahuang6118]

Brilliant mind of engineering. Excellent truth. Thanks

[@aaronza7218]

Really make sense M12 decreases the force amplification of the built-in clamp lever compared to M5 to get the desired or max torque. Thank you for sharing your technical knowledge. Great content!

[@colecoleman1499]

Thanks to youtube algo and your yet another cycling myth busting. It saved me from from diving into through axle part. I have RAF 13 front hub. I don't like QR hanging around. What would be the impact on stiffness if I just use small bolts to tighten instead of QR please

[@douchebagout]

Best video, bar none, explaining the differences between thru and qr.

[@truthseeker8483]

The biggest advantage of the through axle was not mentioned.....the frame has holes that the axle is located in ..instead of open fork ends...this means the wheel always gets clamped back in the correct position ensuring wheel alignment

[@AndrewWalter]

30 years ago linkage forks were a thing. The attempted goal being to keep the fork arms parallel and even. The molded crowns on the one piece lowers were getting bigger and bigger but one sided springs made everything sloppy. When thu-axles appeared it was a game changer to add some moment distribution at the lower fork.

[@tjgraham3597]

Did you know that all modern high end telescoping suspension forks, single crown, double triple crown all have their spring media in one leg and their damping systems in the other? One side trying to always extend and the other side damping slow speed, high speed compression and rebound circuits. 30 years later we have got the sloppy out of single sided springs. And all that is old is new again, crazy huge carbon leading and trailing link forks are trying to come back. www.pinkbike.com/news/structure-cycleworks-linkage-fork-crankworx-whistler-2017.html and now killed by covid19 bikerumor.com/2018/10/25/trust-performance-sends-the-message-brings-linkage-suspension-forks-to-the-forefront/

[@AndrewWalter]

The next test should be to measure the axle deflection while mounted in an mtb fork. Not sure that it would matter on a rigid fork. I like thru-axle on my road bike because I can put the wheels on when it is in the workstand. Makes me happy every time.

[@sshapiro112]

Glorious to have somebody doing videos like these

[@morrisizing]

Guessing most are mistaking the need for more spokes and beefed up forks to deal with braking forces from the disc for stiffness from the through axel.

[@KD_cycling]

Wow. Way to completely miss the point of thru axles. Nothing to do with wheel stiffness. They're used to reduce fork twist under braking. When you brake with discs the force is applied to the left side of the fork (where the caliper mounts) causing the fork to twist and the bike to pull to the left. Probably a minor issue on a road bike but a big deal on a motorbike or MTB with big long forks. This is why many modern motorbikes have dual sided front discs either side of the fork. The thru axles stiffen the fork and IMPROVES HANDLING! That's it!

[@quinngroff7084]

The "thru" axle goes through the axle genius. That is why it has that name, and it allows for larger hollow axles with a larger diameter clamping interface with the frame in conjunction with the wider axle standards (which do improve stiffness) that came into use roughly the same time as through axles. Thru axles also make it easy to get the wheel installed perfectly aligned everytime and cannot slip in the dropout under extreme forces.

[@FightFilms]

No, they don't. They make people lazier and dumber. If you install your QR wheel in the same place every time, the caliper/rotor relationship will be preserved. 30 years of installing bike wheels on frames confirms this. I like through axles, on suspension forks. I see no advantage to that system on frames over 9mm bolt-on hubs.

[@quinngroff7084]

Yah unfortunately not everyone who owns a bike is as capable as you haha. As a mechanic I see improperly installed QR's every single day. It is hilarious to me how resistant some people are to change in the bike world. Thru axles are clearly easier to use, and exist because of large diameter axles.

[@lltany]

Torque caps (the sram standard for MTB) I think “proves” this as well. I imagine the larger surface area of the torque cap helps increase stiffness by making it harder to rock (due to the larger supported diameter). What are your thoughts on torque caps? However I always thought the QR partially relied on the nipple of the end cap sitting in the dropout. Typically when installing the hub in the frame/fork I would make sure these “nipples” were bottomed out on the dropout before tightening the QR. thus the typical vertical-ish loads can be taken by the normal, and the friction. That’s why QRs can be ridden with the QRs being pretty loose. Which is probably one of the things that has lead to the lawsuits and thus the death of qr.

[@SurpriseMeJT]

"Lawyer tabs" yes, are there to prevent the wheel falling out in case where the QR is loose. QR's are not going away because they are unsafe, but because the manufacturers and marketing folks are brainwashing us to buy something different.

[@CyberPun]

Very informative! Now I know the difference.

[@gregtitus2467]

Good stuff! Learned a lot. Thanks.

[@sandykavor8434]

Very true the axle does not carry the load. It solely keeps the hub clamped. However the through bolt is much more robust vs. traditional QR therefore providing safer interface, and most importantly preventing the wheels from coming out of the dropouts. Also, I never understood why bike builders grease the heel out of these. The actual hub axle does not spin on the through axles, so there is no need to loaded with grease.

[@cymikelee]

That's a good question -- makes sense to grease the threads, but maybe some people take "grease your thru axle" to mean the whole thing rather than just the threads?

[@sandykavor8434]

@@cymikelee Exactly. Threads for sure, but body of the through axle not necessary. Both are anodized and made out of aluminum. I learned in msny cases too much grease causes more harm.

[@kieron88ward]

Go old peak torque, always answering the wrong questions. Looking at the only through axle i have: it does form the significant part if the vertical load path (i'm gonna ignore the 1mm lip on the fork which i see only for assisting in putting the wheel in). A through axle will have tighter fitting tolerance than a slot in QR, it's also completely captive rather than an open ended slot (ride a QR skewer undone and a through axle undone and see which moves more). 12, 15, 20mm through axle, all larger in diameter than 9mm so bending at that point will be less even if the 9mm ramps up internally. I think jurnos often talk rubbish but bikes are actually built by engineers that have not only studied these things but tested them too.

[@pokeypaul78]

I’m pretty sure the thru axle was never meant to add wheel stiffness or vertical stiffness. It reduces compliance when leaned over as it helps to maintain the 90 angle between axle and fork leg. Basically preventing it from going parallelogram. As the loads on a MTB are often off center because the tire is wider, these side loads are more common and the thru axle is more important. Road bikes become more responsive when really pumping As you’re not twisting the fork.