Thru - Axle and QR analysed. Stiffer? Hmm.

[@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..."

[@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

[@LawrenceMacMacster]

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.

[@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?

[@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.

[@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.

[@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.

[@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!

[@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.

[@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.

[@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.

[@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.

[@theadventurebiker]

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

[@pavel_zak]

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

[@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.

[@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.

[@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

[@JeffCowan]

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

[@GreatEgretAdventure]

😂

[@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

[@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.

[@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”.

[@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!😂

[@andredegraaf1643]

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

[@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...

[@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.

[@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.

[@ΣΤΑΥΡΟΣΓΚΕΡΛΕΣ]

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.

[@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)

[@lookinforanick]

Thumbs up, thanks for the video. Any chance we will ever see one about the science, and alleged stiffness differences, between different pedal cleat systems?

[@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.

[@ΣΤΑΥΡΟΣΓΚΕΡΛΕΣ]

​@@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.

[@jasonrodwell5316]

What about the fact that in a thru axle interface the dropout is enclosed as opposed to open with qr, would that not limit slippage too resulting in a stiffer interface?

[@DanHoopes211]

What about the argument that through axles unify the dropouts to create a stiffer construct inside of which the wheel lives?

[@lawrencesingleton2153]

Exactly right. He just glosses over this. I don't think anyone has been saying the wheel itself would be any stiffer?

[@johnegregg]

I think that’s what the clamping is that he’s talking about. The problem is how to get it tight enough. The DT Swiss lever he mentions doesn’t have enough leverage.

[@DanHoopes211]

@@johnegregg I don't think that's what he's referring to. I think what he's talking about is the ability to create a good interface between one side of the dropout and the hub flange. Not about attempting to unify the dropouts into a single construct. Because with what he's talking about, the QR accomplishes it more effectively to and I'm going to have a really hard time reasoning that a QR more effectively unifies one dropout to the other. Maybe the reason that thru axles can get away with shorter levers is that they don't need to be as tight as QR's to accomplish what I'm talking about as effectively.

[@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.

[@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.

[@cd0u50c9]

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

[@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.

[@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...

[@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.

[@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.

[@jonathanwoo6597]

Thanks for the video! But could you explain why the same 4nm torque on the M5 QR generates twice the clamping force as the M12 thru-axle? That seems very counter-intuitive.

[@davidmarshall2399]

Probably thread pitch / angle differences.

[@willo7979]

The 4Nm torque that PT refers to, should be QR lever torque, not a screw tightening torque. This torque on QR, is taking advantage of a cam in the QR, ramping the axial pull on skewer up many folds hence the clamping force. But I believe PT is using the same calculation as M12. For M12 Thru Axle, it is a direct screw torque, hence you really need to tighten it as per suggested by manufacturer to achieve the same and desired clamping force. However, it's a broken system for many niche and unreliable manufacturers, because they either they don't know what they are doing, or they are closing one eye, or both.

[@jonathanwoo6597]

@@willo7979 Thanks. I was wondering about that. When I re-played the part where he did the calculation, the only thing he changed was the screw diameter. I don't recall him making any other calculation changes. But I can see what you wrote is the only plausible explanation.

[@robinrai4973]

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

[@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.

[@johndef5075]

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

[@JulianIrwinX]

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

[@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.

[@ms.karihart2983]

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

[@josemorenoporras7506]

11:30 I quickly check my 2020 Specialized Enduro manual and the torque spec for the 12mm rear axle is in the chart: 6mmHex/133 in-lbf/15 Nm. In my older mtb bikes it was something like that too.

[@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.

[@ΣΤΑΥΡΟΣΓΚΕΡΛΕΣ]

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

[@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

[@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.

[@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.

[@Wacoal34d]

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

[@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.

[@ThunderStruckMTB]

How about a standard 15mm end cap hub on a Rockshox fork with the oversize Torque Cap drop outs? When the smaller (standard) end caps are seated into the over size (Torque Cap) drop outs the whole thing flops around until the 15mm thru-axle is located, so in this case, is it fair to say that the axle is taking the vertical loads because the end caps do not mesh in any way with the fork drop outs?

[@_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!

[@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.

[@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?

[@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

[@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.

[@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

[@gr8fulride]

I ride mtb. quick release on one aluminum frame always slipped in my rear dropouts on rougher trails, grinding away at them and allowing the tire to hit the frame. I'm so happy for through axles as I've not experienced that kind of slippage since giving away all my mtbs with quick release skewers. I've got a Santa Cruz Hightower and have had its through axle loosen up on two occasions so I'm extremely careful to check it every ride.

[@theadventurebiker]

I ride MTB too. I have a full-sus bike that is now 9 years old with quick release wheels (font and rear). The bike has over 35,000 miles of riding on every type of terrain imaginable. I have never had any issue with its QR axles. Not. One. Single. Time.

[@gr8fulride]

@@theadventurebiker that's some high mileage. I can flex it at will on the bike I gave my brother, but he never has any issue. Navarro ponderosa hardtail. he's slightly heavier than me . 245 vs my 220 lbs. he's had the bike for five years now and no problems. he replaced the back rim, as I had bent and retrued it, then he bent it. happy trails

[@theadventurebiker]

@@gr8fulride I have 3 bikes right now - 2 aluminum full suspension (which actually have the same rear end), and 1 steel hardtail. All 3 have traditional open dropouts with 9mm quick release axles on the rear (one of them does have a thru-axle on the front). 2 of them are tandems. The wheels on all 3 bikes are rock-solid. Our combined total rider weight on the tandems is 325 lbs and we still have zero problems or flex with the traditional quick release axles even when riding technical off road terrain. You can see us on our steel hardtail tandem in this video if you'd like: kzbin.info/www/bejne/jnjKmoWplLl6jKc My other bike that has the 35,000 miles can be seen in some videos on the channel I am posting from here like the following one where I pulled a trailer (hitched to the rear axle) loaded with over 40lbs of cargo and still had zero issues with any unwanted flex etc kzbin.info/www/bejne/oZDTnXt9jtB5gNU (I've also pulled this same trailer with our steel tandem as well...same result). Cheers man 👍

[@toddlovell9711]

Sounds like you never installed the QR skewer right. Most people do not install them correctly and I was one of them. When the LBS showed me how I never had an issue after that. no matter how gnar

[@gr8fulride]

@@toddlovell9711 got a quick release on one hardtail that is holding up . It was just that one bike has more that average flex in the rear frame so it was never gonna work for me without some heliarc mods. On a brighter note, I broke my Cannondale bad habit frame on a three in a row 2 foot drop line. Basically a blue trail . That bike had through axle. Sold it after replacing the frame.

[@aim-at-me]

Hey man really interested in your bolt calc, can you go into a bit more depth on why smaller bolts give higher clamping loads for the same torque?

[@thetigers2803]

I wanted to know this too so I read up on it. I think it's because friction is the primary limit between bolt torque and tension. So a larger bolt simply creates more friction (in the threads, under the bolt head etc?) than a smaller one at the same torque. This then limits the tension you are getting. This is different to how much ultimate tension you could create if you varied the tightening torque. So really the limit is a practical one - how much pain can you endure with your multitool.

[@willo7979]

Tightening a bolt by rotation is actually an act of converting rotation motion to axial pull in length on that same bolt, this micro-extension in bolt is inducing tensile force in the bolt itself and, for the whatever body it is clamping on, this is felt as clamping force (in this case, it is whatever is being clamped between the two forkends). And to achieve the same clamping force on newer design (TA) compared to old design (QR skewer), the torque required is proportionate to the diameter of the bolt (given lubrication factor stays the same, ie. if lubed, lube on both). Hence, comparing a TA bolt of 15mm to a skewer of 5mm, TA bolt requires 3 times higher tightening torque (12Nm), approximately. The concern in this article, is that, for a TA with a short built-in fixed lever, it is hard to achieve 12Nm by hand without a tool (eg. spanner) with longer arm, especially when riding out. Personally, i do not think lower torque on TA is an issue, as long as it is 'hand-tight'. This is backed by the reason that TA comes in a system where forkends are no longer having dropouts, thus the wheel, the hub and TA has extremely low chances of separating from fork, thus this type of incident has extremely low chances owing to the significantly higher safety margin.

[@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.

[@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.

[@nrhudec]

Can you make your bolt calculator spreadsheet downloadable? It's really nifty!

[@JacobSkriver]

Totally agree about the load path and how the thru axle doesn't add anything to the stiffness really. But there's something odd about the bolt calculation: why would a larger bolt give a lower clamping force with the same torque?

[@tgoods5049]

Why am I looking at PowerPoint slides on a Saturday night?

[@Cyclonut96]

The PowerPoint was not done well enough for me. A bunch of terms not well understood, no picture, a couple of lines not making sense until he starts talking about them, and the red, what red? Picture is worth a 1000 words, but for me this was not selling the message.

[@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!

[@Dyoochoob]

Question: Ti skewers are often said to give a "noodly feeling" and cause more brake rub due to the lower Young's modulus compared to steel, but if there are no signs of slipping in the dropouts, how can this be so? I suspect it's bs but, is it possible that the lower clamping force allows a bit of movement so that the the end-caps are momentarily off parallel with the drop out, but without full blown slippage occuring.

[@tomeklubomir]

I stopped using a Ti QR skewer on the rear wheel on my bikes and the brake rub is away. Don’t think it’s the titanium’s fault used in the axle but the lack of material/strength in the aluminium end caps (I used PlanetX Ti skewers). I’m able to wobble the rear wheel with my hand after doing them up fairly tight (try it). If so go back to standard manufacturer spec, where there’s a lot more material in the end caps, which spreads the load better and clamping force is stronger. It doesn’t pose a problem at the front though...

[@monsterinyourcloset7573]

This is a good question. I always assumed it was because of the lower Young's modulus combined with a the higher elastic limit of titanium. Once Young's modulus is exceeded through lateral stress, the rider feels a "noodly" change at the axle, but once the stress is removed (such as straightening out after a hard turn or slowing after a hard sprint) the titanium skewer returns to its original dimensions and the "noodly" feeling goes away. Would be difficult to test in a laboratory setting tho, considering the magnitude of the forces involved.

[@yonseimatt]

I use titanium 5mm skewers and have had no issues whatsoever, but they have an Allen end on them, not a QR lever. The titanium hex head is annoying actually because it's softer than steel so I'm always worried about rounding it if I overtighten. Been using them over a year, no problem. I weigh over 85kg and can put out a fair bit of power in a sprint.

[@Dyoochoob]

@@yonseimatt yeah, you can probably achieve the same clamping force as a steel skewer but the problem would be resisting any additional load in the skewer. As monsterinyourcloset says it may be difficult to test. A camera fixed on the rear stays for some sprints might reveal something.

[@janeblogs324]

1:30 is that wheel on the left laced correctly?

[@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.

[@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!

[@normanmadden]

I had issues with 135mm QR coming loose under load, and mis-shifting; my new frame is thru axle and has no issue with the wheel movement.

[@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.

[@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.

[@thecakeisalie7070]

For QR, I noticed that the load is carried by the bit that interfaces with the dropout, the 9~10mm bit on the hub. For TA, I've always wondered why there's a shear plane between the frame and the hub endcaps. Now I understand that a TA is a clamping component and only if the clamping force is exceeded, the structural stiffness of the TA comes into question. So if TAs were developed due to many broken QRs, did the industry misdiagnose the causes? Is it now more likely that untightened TAs go unnoticed, causing shearing through a weak part?

[@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.

[@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.

[@MrBunglor]

Fascinating explainer, I have questions. Understanding that the end cap/dropout interface needs to be well clamped and accepting that the 4nm clamping force provided by the DT key in the field is going to be far less that of a QR skewer, have manufacturers already factored this in? eg at 4nm hand tight are we getting as stiff as is required, the end cap is not loose in the dropout and will not shift, and it is limited gains beyond this? Secondly, is there any effect on material fatigue, do higher clamping forces tension the forks or rear stays in a different way that may be worth considering?

[@BigDanDCNation]

I'm an electrical engineer, not a mechanical engineer, so this was extremely helpful and insightful. Your analysis all makes sense. I had visualized what you have described here as the possible strength dilution but I didn't have the formulae or analysis to prove it to myself, so thank you. BUT given this awesome analysis, would the forces on wheels, the rigid fork, and the seatpost be unidirectional enough to make the use of carbon fiber in these parts a good place to save weight?

[@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.

[@earthstick]

Most thru-axel designs I have seen have a closed dropout (not actually a drop - out) whereas QRs have an open dropout. Is there any effect from that? My guess is it is only a benefit if the wheel is not clamped adequately.

[@willo7979]

yes a closed forkends is the whole point, and 'Thru Axle' sounds better the old 'skewer'. can't think of any better names really. and that closed forkends are for safety especially on fork with disc brakes. and this is being very consistent in latest bike line up across major brands, and you don't see this on their latest rim brake models, it's definitely a disc brake thing. yes this is significantly safer even if the wheel is not clamped adequately. as pointed out by PT, if it's hand-tightened, it is likely not having clamping force as high as QR, but still, it's acceptable. until new problem's found:), like: 1. you already saw that in TDF race, failure to remove wheel during mid-race wheel change, because they were tighten up-to-spec by bike mechanic at workshop with long spanner that you simply can't undo it with the built-in short 7cm lever, unless it's a QR-type Thru Axle designed by more reliable sources (eg. shimano?). 2. while moving away from conventional QR, many entry level Thru Axle have shown design flaws, some stuck, some with stripped hex head (i couldn't recall when was the last time such a large torque is spec'd on a large yet shallow hex head, on aluminum alloy), some with broken threaded section from the rod at neck section.

[@sshapiro112]

Glorious to have somebody doing videos like these

[@cubist112]

Very informative. How about the Mavic Speed release axles? Do they clamp tight enough?

[@nstrug]

If you do them up to the recommended 10Nm then yep. If you get the ones with the built in lever, the lever clicks round once you hit 10Nm, it’s effectively a built in torque wrench. Clever design.

[@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.

[@yonseimatt]

A thing I'd like to see addressed though is the stiffness of a suspension fork with 5mm vs 15mm. Surely it's the larger clamping surface diameter you get with a bigger thru bolt that contributes to the stiffness? I'm sure I'm not explaining it very well, but when Marzocchi made their first USD fork (Shiver, IIRC?) they specced a large diameter thru bolt, I think 20mm, because anything smaller made it feel noodly. I guess it makes little difference with the rear dropouts as they're one corner of a triangle anyway so not subject to moving away from each other they way that the more independent legs of a fork are.

[@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...)

[@jbthomson89]

Great explanation! Any idea what torque setting pro mechanics use on their impact drivers for road disc wheel T-As? I imagine they’ll use the same regardless of whether they’re on the road or in the service course

[@osh241]

Cool, I assumed the wider axel increased the load face of the hub shell helping clamping and reducing twisting between bars and fork leg. MTB days anyway.

[@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

[@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!

[@OYeahan]

Hi. Could you please explain how is the clamping torque affected by the Rockshox screw-in + lever "through-axle" system for front forks? The bolt torque itself is quite low as there is only a short lever, but then the lever cam is used to push a wedged element into the "through axle"'s non-disc side interior, and this expands the through-axle and makes a pressure-contact with the non-disc fork leg's "thru-axle hole". I was wondering if this cam system's purpose is only to prevent accidental unscrewing of the "through axle" (which could be possible due to the rather low clamping force attained from the threads due to the short lever) by creating a "friction lock", or if it maybe also provides additional clamping force? I always screw it in quite hard, but the way the rotating lever interfaces with this alu slot in the thru axle suggests that the axle is intended to be screwed in with quite low torque (sort of let's say a few Nm), and then somehow clamped... I guess I could always make an experiment - screw it in so that the wheel has some play and then set the cam up so that it will lock it in place, and see if the play is reduced/gone - but I never tried that yet.

[@norman-gregory]

With Mtb is it not safer with the Through Axel? This would be a major reason why people change and move away from QR.

[@pauldamian2988]

How about an analysis of just what a quick release lever means to the tension of the shaft? I guess I am not so sure your 4 Nm equivalent is there? Always good stuff! Thanks!!!!!

[@willo7979]

just a guesstimation: 5mm skewer, cam lever extends skewer length by say 0.3mm of total length the cam provides (between lever at 80deg and full close), CrMoFe. that's 5-10kN of shaft tension. In reality it's a little more complex than a few lines here.

[@123Purple]

would the load path be different for a bolt on hub such as a fixed gear rear hub?

[@dperreno]

I would also add that the larger diameter thru-axle drives a larger diameter axle, thus improving stiffness (at least on the rear hub).

[@imrostoffa9077]

How about twisting loads during heavy cornering on mtb between fork legs? ...

[@jetplaneflyer]

The stated torque for my 12mm thru axles is 20Nm which for which I use a torque wrench. That would be about twice the clamping force of a QR by your own calc. If people dont tighten them enough, that's hardly the fault of the thru axle is it? Also one thing that you didnt consider - the close fitting thru axle inside the hub axle will stiffen the hub's axle in bending.