Why Thru-axles on Road Bikes?

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WyvernRH
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Why Thru-axles on Road Bikes?

Postby WyvernRH » Mon Jul 30, 2018 1:00 pm

Having witnessed more than one abysmal rear wheel change on disk braked bikes in the TDF this year I was given to wonder why manufacturers went for thru-axles on road bikes - especially at the rear wheel. Now while I understand the research where the MTB's were loosening the front Q/R and in extreme cases popping the wheel I am not sure the same would happen in road bikes with no suspension at the front and pretty sure never at the back, as the forces would surely push the rear axle back into the vertical drop out?

Having had a bit to do with motorbike disc brakes when they were 'new' back in the 70's the obvious answer to me would be to reverse the position of the caliper on the fork so it 'leads' the axle and so (as in the rear) pushes it back into the dropout?
Other fixes for the front come to mind such as:
- re-orientating the dropout slots to face forward a bit?
- lawyer lips on the front dropouts (yeah sad I know...)
- Upping the leverage ratio on the q/r's to make the lock pressure higher.

Still, moving the caliper seems the good engineering solution?

I have been bashing around the Williams and Hunter valleys on a FELT cyclocrosser with disks and q/r wheels fro a couple of years now and after all the fuss I check the q/rs religiously at every stop but have never found a loose q/r Maybe cos I do them up pretty tight? Nor have I met anyone who has had the problem on a road bike (or MTB come to that but I do not mix much in those circles)

So, have I got it totally wrong or are these new thru-axles just piece of over-engineering to make us all buy new kit? :P

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Mububban
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Re: Why Thru-axles on Road Bikes?

Postby Mububban » Mon Jul 30, 2018 1:36 pm

Plenty of bike reviewers reckon a thru axle makes the front end of the bike noticeably stiffer and better handling. No personal experience though.
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Re: Why Thru-axles on Road Bikes?

Postby familyguy » Mon Jul 30, 2018 1:46 pm

Yeah, apparently stiffness is the bonus of a front thru-axle, with the primary being the few QR issues that occured. Quite a few front disc QR bikes now have almost forward facing dropouts as you suggested, further countering this issue. For road use, mostly overkill. Stil, I'm happy to score cheap QR disc wheelsets for years to come to keep a bike on the road.

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Re: Why Thru-axles on Road Bikes?

Postby 10speedsemiracer » Mon Jul 30, 2018 3:05 pm

My understanding is that T/A is designed, in a road bike context, to counter the forward stresses and torsion effect on the non-drive side fork by the disc caliper, which was thought to risk popping/unwinding a Q/R skewer in extreme usage. In reality I think that this is a case of manufacturers creating a new must-have line of tech along with the associated marketing (or mucketing as Duck so eloquently puts it).

I can envisage this scenario, maybe but only in an absolutely extreme scenario although would have thought the rider would be over the bars or off the bike before there would be enough fork deformation to cause the wheel to become unmounted..

Also think that in a race context that this would probably result in more spare bikes being used, as opposed to wheel changes.
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Re: Why Thru-axles on Road Bikes?

Postby ironhanglider » Mon Jul 30, 2018 7:14 pm

10speedsemiracer wrote:My understanding is that T/A is designed, in a road bike context, to counter the forward stresses and torsion effect on the non-drive side fork by the disc caliper, which was thought to risk popping/unwinding a Q/R skewer in extreme usage. In reality I think that this is a case of manufacturers creating a new must-have line of tech along with the associated marketing (or mucketing as Duck so eloquently puts it).

I can envisage this scenario, maybe but only in an absolutely extreme scenario although would have thought the rider would be over the bars or off the bike before there would be enough fork deformation to cause the wheel to become unmounted..

Also think that in a race context that this would probably result in more spare bikes being used, as opposed to wheel changes.


Popping an axle out under braking is heard of in tandem circles, however it is usually an accumulation rather than a single event scenario. I suspect that modern lightweight QRs that don't hold as well as the traditional internal cam type don't help. TA designs are more idiot-proof, but there are some high level idiots out there.

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Re: Why Thru-axles on Road Bikes?

Postby robbo mcs » Mon Jul 30, 2018 8:08 pm

I have disc brake road bikes with QR and through axle. I much prefer the through axle. It better centres the wheel when putting it on. That is more of an issue with disc brakes, as if it is not perfectly centred there may be rub. Also, the through axle is one piece, so it is pretty hard to lose. I am sure we all have had the experience of a QR skewer coming apart in the back of a car or on the side of the road, then trying to find a spring etc.

Just my 2c worth. I have not really noted any difference in the ride. Also, I have never had a problem with a QR system coming loose whilst riding etc

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Re: Why Thru-axles on Road Bikes?

Postby Thoglette » Mon Jul 30, 2018 9:18 pm

robbo mcs wrote: I am sure we all have had the experience of a QR skewer coming apart in the back of a car or on the side of the road, then trying to find a spring etc.

No, not in several decades. In fact, first I've ever heard of it happening. But then none of my forks have "lawyer lips". YMMV
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Re: Why Thru-axles on Road Bikes?

Postby Calvin27 » Tue Jul 31, 2018 10:00 am

I rekon thru axles are a nice addition and noticeably stiffer than all that BB and headset bs we get sold. If you only ride road you have no idea how good it is to only have one TA standard. I think for the most part most wontnoice the stiffness, but the big one for me is the alignment of the disc rotors. QR can be incredibly picky to small changes that a qr cam can change (i.e. tight or loose). Most people talk about the front end but I rekon the rear end stiffness is just as important and noticeable.

WyvernRH wrote:So, have I got it totally wrong or are these new thru-axles just piece of over-engineering to make us all buy new kit? :P


If you want an example of that, see how mtb hubs went from 100/135qr to 100/142mm TA to 110/148 'boost' and now 'overboost' in the space of a few years. And that was with an already existing DH standard before the whole thing came about!
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Re: Why Thru-axles on Road Bikes?

Postby lone rider » Tue Jul 31, 2018 3:17 pm

Have used both on MTB's and would choose thru axles every day of the week and twice on sundays. As far as road bikes go I have never felt the need for disc brakes so QR V TA is a moot point.

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Re: Why Thru-axles on Road Bikes?

Postby human909 » Tue Jul 31, 2018 9:02 pm

Stiffness improvements in the axle might be noticeable but is it non negligible really performance improving in race conditions? Likewise about the benefits of the disc setup themselves. Wheel change speed can potentially end a race.

(Another reason for thru axles could be due to the eccentric load on the forks from disk brakes. The rigidity from the thru axle likely helps spread the load onto the other side of the fork, in its absence you might need to have beefier fork.)

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Re: Why Thru-axles on Road Bikes?

Postby 10speedsemiracer » Tue Jul 31, 2018 9:09 pm

If you wanted to engineer the eccentric torsional forces out of the equation at the front, two small discs (one either side of the hub) would be a more elegant solution, but then smaller discs will in all likelihood have more issues with heat dissipation. But it would solve the issue of one-sided forces trying to wishbone the fork. Hmmm, just thinking.

And then there's the issue of front fork spacing and hub width (probably need to go to 110mm) along with the extra 500-600gm of unsprung weight.
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Re: Why Thru-axles on Road Bikes?

Postby eeksll » Tue Jul 31, 2018 9:44 pm

I use QR on all my bikes, rim brakes, cable disc brake and hydraulic disc brake.

I do spend an extra few seconds to make sure its centered in properly. and when the rotor rubs on the brake pads its a bit of "is that me not doing the QR up properly?" "have my avid brakes gone screwy again" etc

so if thru axles are idiot proof in terms of alignment, at least its one part i know is right. Nothing wrong in making something better/easier.

I am not so much a fan of screwing it into the bike frame/fork any chance of cross threading there?

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Re: Why Thru-axles on Road Bikes?

Postby robbo mcs » Wed Aug 01, 2018 6:09 am

eeksll wrote:I am not so much a fan of screwing it into the bike frame/fork any chance of cross threading there?


That is my one concern about the setup. If you stuffed the thread, I don't think it would be feasible to tap a new one? I am careful to make sure the end of the axle is clean and free of grit etc before I screw it in.

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Re: Why Thru-axles on Road Bikes?

Postby bychosis » Wed Aug 01, 2018 6:53 am

Sure it’s an improvement in stiffness and location of the wheel, but it’s incremental rather than revolutionary. What is ridiculous is that ‘they’ decided through axles we’re good for road bikes and used the mtb design which was good, then mtb design promptly moved on to a new ‘standard’
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Re: Why Thru-axles on Road Bikes?

Postby JPB » Wed Aug 01, 2018 8:13 am

I have disks and QR on my road bike and it can be frustrating replacing the wheel and getting things aligned after fixing a puncture on the side of the road in the dark.
If thru axles make alignment more positive it will possibly be faster for a muggins like me instead of faffing about repeatedly opening and closing the QR while saying mystical incantations.

I heard Robbie McKewen's commentry on a thru axle wheel change during the TDF. Maybe he is not a fan but that is at pro level.

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Re: Why Thru-axles on Road Bikes?

Postby baabaa » Wed Aug 01, 2018 8:46 am

bychosis wrote:Sure it’s an improvement in stiffness and location of the wheel, but it’s incremental rather than revolutionary. What is ridiculous is that ‘they’ decided through axles we’re good for road bikes and used the mtb design which was good, then mtb design promptly moved on to a new ‘standard’


Don’t forget that some of the higher quality hub makers ( CK , Phil, Hope...) still offer bolt-on / fun bolt options so you can keep that "standard" but just ditch that qr lever.
These allow you to set and snug your wheels in the dropout so they don’t ping the rotor and then firm them down.
I never have a team car following me so have no understanding of the angst to make that extra fast wheel change. I would say the on and off takes about the same time as a qr and although you need to carry an allen key, may even give better parked bike thief deterrent.
Hardest thing will be to trying to find a frame set of that standard in the next few years. Should be a bonus for smaller frame builders for people who cannot see or have the need for all this ever increasing stiffness stuff.

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Re: Why Thru-axles on Road Bikes?

Postby MichaelB » Wed Aug 01, 2018 8:49 am

I think at the end of the day, it's like many 'improvements' seen on bikes. marketing led that usually make it cheaper to make the bike (less manufacturing cost, reduced parts count, quicker to assemble etc) or provide the ability to charge more.

Probably makes a difference, but is negligible in terms of discernible performance, like many things on the bike.

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Re: Why Thru-axles on Road Bikes?

Postby find_bruce » Wed Aug 01, 2018 8:53 am

JPB wrote:I have disks and QR on my road bike and it can be frustrating replacing the wheel and getting things aligned after fixing a puncture on the side of the road in the dark.
If thru axles make alignment more positive it will possibly be faster for a muggins like me instead of faffing about repeatedly opening and closing the QR while saying mystical incantations.

I heard Robbie McKewen's commentry on a thru axle wheel change during the TDF. Maybe he is not a fan but that is at pro level.

Have you tried (1) insert wheel (2) apply brake (3) close the QR ? Works for me to avoid any faffing about

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Re: Why Thru-axles on Road Bikes?

Postby Calvin27 » Wed Aug 01, 2018 9:26 am

eeksll wrote:I am not so much a fan of screwing it into the bike frame/fork any chance of cross threading there?


Nope. You'd have to be really ham-fisted to stuff the thread. You don't need much force to actually turn the thread - it's a lot easier to do than even normal bolts with allen keys.

MichaelB wrote:Probably makes a difference, but is negligible in terms of discernible performance, like many things on the bike.


On my dual suspension it makes a world of difference. All of a sudden designers can do split pivots at the rear and the rear end is generally a lot nicer with TA. On my roadie, I think I can feel a difference, but to be honest not surprised if I failed a blind test. I mean which new bike DOESN'T feel nicer?!?! :?:
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Re: Why Thru-axles on Road Bikes?

Postby chriso_29er » Wed Aug 01, 2018 10:04 pm

eeksll wrote:I am not so much a fan of screwing it into the bike frame/fork any chance of cross threading there?


They dont screw directly into your frame it has a captive nut.
Even trying all the tricks (holding brake etc) I have from time to time had alignmetn issues on the front of my QR/disc bike.
I find the throuh axle on my other bike actually faster and none of the alignment issues.
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Re: Why Thru-axles on Road Bikes?

Postby jasonc » Sat Aug 04, 2018 8:53 pm

10speedsemiracer wrote:If you wanted to engineer the eccentric torsional forces out of the equation at the front, two small discs (one either side of the hub) would be a more elegant solution, but then smaller discs will in all likelihood have more issues with heat dissipation. But it would solve the issue of one-sided forces trying to wishbone the fork. Hmmm, just thinking.

And then there's the issue of front fork spacing and hub width (probably need to go to 110mm) along with the extra 500-600gm of unsprung weight.

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Re: Why Thru-axles on Road Bikes?

Postby 10speedsemiracer » Sat Aug 04, 2018 9:01 pm

jasonc wrote:
10speedsemiracer wrote:If you wanted to engineer the eccentric torsional forces out of the equation at the front, two small discs (one either side of the hub) would be a more elegant solution, but then smaller discs will in all likelihood have more issues with heat dissipation. But it would solve the issue of one-sided forces trying to wishbone the fork. Hmmm, just thinking.

And then there's the issue of front fork spacing and hub width (probably need to go to 110mm) along with the extra 500-600gm of unsprung weight.



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Re: Why Thru-axles on Road Bikes?

Postby jasonc » Sun Aug 05, 2018 8:15 am

Sadly pure concept
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Re: Why Thru-axles on Road Bikes?

Postby Duck! » Sun Aug 05, 2018 7:36 pm

Why through-axles? Gumby-proofing as much as anything.... Properly-secured quick releases are perfectly fine. The problem is that they're open to a great variation in clamping force, and a lot of people simply don't do them up properly.

By being fully-encircled, through axles remove the ability of the axle to "walk" in the dropouts if not secured properly.

They also allow manufacturers to use the same hubs for both road and non-Boost MTB.
I had a thought, but it got run over as it crossed my mind.

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Re: Why Thru-axles on Road Bikes?

Postby jasonc » Sun Aug 05, 2018 8:06 pm

Duck - also means the disc goes in the exact same spot Every time. So no need to adjust the brake caliper
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