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
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.
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.
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
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.
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.
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.
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.
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.
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
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
@@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.
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.
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...
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.
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!
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....)
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.
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.
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
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.
@@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.
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.
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.
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.
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.
@@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.
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.
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
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.
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.
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!
Another great video and explanation! The QR in my country is actually called a 'clamper' or a 'tightener', so the name went over to the TA system as well, which is the correct naming for something that clamps :)
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.
Another excellent video. I like the through axle for accurate alignment. Drop outs do where and it can be fidley to align the wheel with a qr. Unsprung weight on a suspension fork probably better of with a qr. Pros and cons as usual.
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 !
@@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
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.
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 👍
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.
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.
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!
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.
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!
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
@@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
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!😂
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?
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 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.
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.
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.
@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
@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.
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.
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.
@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...
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.
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.
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.
@@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
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.
@@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.
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.
Thanks for this great video of yours! Really opened my eyes and instantly checked everthing related to the Thrux-"Axles" on my bike :D Regarding the torqueing one can do with the little lever from DT: when doing it up really good I actually did achieve the recommended min. Torque of 15 Nm (checked with my torque wrench). The other thing I noticed when reading through the manual from DT Swiss is that the threads should NOT be greases. Thats a good thing to take note of, mine came with a good amount of grease on the threads...
EDIT: Since the Thru-"axle" thread was greased, I assume that the "actual torque" is a bit higher. So in the end I think it is realistic to beleive that one can indeed fasten the thru-axle appropriately with the provided lever
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.
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?
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.
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!
Hi, the info in your video are so precious that it would be worth the effort (also for the popularity that your channel deserves) of adding some more "layman" explanations or recap for people who are not familiar with engineering concepts!
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!
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.
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
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.
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.
@@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.
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.
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...)
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.
Great video. I don't 'like' tons of videos but this is a great myth buster that to me makes sense. Good work. Still have a Cervelo 2016 S5, rim brake and mechanical. Not enough meat on the bone for me to change to di2 and disc brakes right now as it still holds its own. Also price kills any idea of the upgrade. Parts availability will be the nail in the coffin. But that's what the industry want I suppose. Take care and keep up the good work.
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?
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.
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/
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.
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.
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
@@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?
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.
I was just going to leave a link too Hambini's site as you two must of fell out of the same engineers vat! Low and behold he commented here about an hour ago!!! haha Love the content from both of you guys! When you just need to know everything about bicycle engineering we all have two sites to visit!! Yo Hami you guys should team up on some content
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.
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.
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
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.
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.😱
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
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.🤓
Hey love your videos! Just wondering, is the real axle of thru axle hubs larger in diameter than the axle on a qr? If so why would that not make it stiffer? I'm not personally invested, seeing as I'm sticking to qr either way, I'm just curious. I'm also curious about bolt on axles? Where do they lie in this comparison?
Love this and very informative! Thanks! I would say most MTB forks come with a 15mm with a camming action QR lever, what torque does this normally achieve? All my rear 12mm through axles are bolt in and marked to torque to 12Nm.
I believe the "camming action QR lever" does not effect the clamping force at all, but is used as an expanding wedge(collet) to lock it into the non-threaded dropout for axle alignment and to prevent loosening.
I enjoy your analysis' very much. They do confirm my odd combination of old and new tech is actually dead on. I go with old style bolt on wheels. Now that does have your desired clamping load and much simpler engineering. Along with this, and I am sure you could do an analysis, that shows the advantage of sealed bearings on rotational friction versus cone and ball bearings is so minimal that the bolt on axle is the way to go. But then I stick with 80s/90s MTB lugged steel frames and 26" wheels. I am not racing and going faster is not my main goal, it's durability.
