One Thru Axle to Rule Them All?

Discuss light weight issues concerning road bikes & parts.
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edwardk
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Joined: Sat Sep 09, 2006 11:30 pm

by edwardk

I now have my first road bike with disc brakes (Campy) (discussion here, https://weightweenies.starbike.com/foru ... 4#p1442824). I have no complaints, other than the nuisance of buying adapters for my bike trainer, my repair stand, etc. It's even possible that I might end up preferring the discs, but it's too early for me to have reached a judgement on that.

Regardless of the general disc vs rim brake forum wars, it does seem to me that disc brake technology brings with it one undeniable benefit, which is thru axles. They locate the wheel relative to the centerline of the frame with infiinitely greater precision than do quick releases, they don't lead to user error in over or under clamping the quick release, and they stiffen the fork/wheel combination with no weigh penalty. So my simple question is, why not offer rim brake frames with thru axles? Why isn't that a logical place to end up? Most of us are not followed by team cars doing wheel changes in seconds, and in any event thru axles aren't all that slow.

What am I missing?

Edward K

by Weenie


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Calnago
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by Calnago

I guess you're just missing the idea of a "Quick Release" skewer in the first place. It's quick. Plus, you don't need the added stiffness between the fork dropouts to counteract the assymetric braking forces caused by the actual braking forces from a disc rotor being skewed to one side. Yes, a thru axle ensures that you will have the wheel centered, but I don't know of any experienced rider who can't slam a wheel in some dropouts with a quick release up against the dropouts and clamp it down perfectly centered. Although I will admit to having pulled some wheels out of less epxerienced riders's bikes and asking them if they knew they'd been riding with their wheel not in straight for a long time. They usually answer with "no, I didn't know that". And that's one of the benefits at the pro level, is that there's much more leeway in the preciseness of the wheel fit after a wheel change with a rim brake bike. With discs, there is no leeway... it'd better be precise or you will definitely know it.
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C36
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by C36

Earlier today I posted a similar answer to another topic.

I am not sure TA bring more stiffness per se.
In MTB with 2 indépendant forklegs you had movement in between the 2 fork legs via the hub. On a road bike if there is no relative mvt at the fork/hub interface then I am not seeing a real stiffness gain.

Now we may end up with more stiffness cause the forks and frames are build stronger to support disc constraints. But that would be independent from the axle itself.

Just thought that on track bikes I don’t recall any TA (easy on fork, a bit tougher on the rear).

Regarding the wheel position, Klein tried to answer this problem with their “rear entry” dropouts. A bit slower to engage the wheel but no options to misalign.



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edwardk
Posts: 32
Joined: Sat Sep 09, 2006 11:30 pm

by edwardk

Calnago wrote:
Mon Nov 19, 2018 8:53 pm
I guess you're just missing the idea of a "Quick Release" skewer in the first place. It's quick. Plus, you don't need the added stiffness between the fork dropouts to counteract the assymetric braking forces caused by the actual braking forces from a disc rotor being skewed to one side. Yes, a thru axle ensures that you will have the wheel centered, but I don't know of any experienced rider who can't slam a wheel in some dropouts with a quick release up against the dropouts and clamp it down perfectly centered. Although I will admit to having pulled some wheels out of less epxerienced riders's bikes and asking them if they knew they'd been riding with their wheel not in straight for a long time. They usually answer with "no, I didn't know that". And that's one of the benefits at the pro level, is that there's much more leeway in the preciseness of the wheel fit after a wheel change with a rim brake bike. With discs, there is no leeway... it'd better be precise or you will definitely know it.
I understand that QRs are pretty quick, but so what? If I don't have a team mechanic following me with a fresh wheel, what difference does the extra 10 seconds matter? And of course some thru axles have levers, making them very similar to QRs in speed.I've seen riders who didn't understand QR mechanics, whose front wheel was held in place solely by the 'lawyer lips' that we all deride, and others who, as you say, are unaware just how misaligned their wheels are. I think the 'quick' aspect of QRs is greatly oversold in practice, at least for the overwhelming majority of us.

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Calnago
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by Calnago

Fair enough. I just like flipping a lever and the wheel falls out, for throwing in a repair stand, a car bike rack, or just cuz it's instant. Although lawyer lips (which are filed off on all my bikes), completely negate the quick release aspect as well, so given that then yes, sure... no reason not to have thru axles on both if you like. But as long as I can file off the lawyer tabs, that's how I like to roll.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
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bilwit
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Location: Seattle, WA

by bilwit

I actually love thru axles and the guaranteed stiffness you get out of them (some of these WW QR skewers can be finnicky at best over time). The thread pitch standard is kind of a huge mess though and needing to buy a whole new frameset and potentially hubs (though most should only require an endcap replacement I think) would be a pain in the ass for a relatively small benefit. I've found that a bolt-on skewer works almost just as well practically.

AJS914
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by AJS914

I agree with C36. I don't see how thruaxels by themselves could make a road bike much, if any at all, stiffer.

I think the real answer is that the bicycle industry doesn't need a 3rd bastardized step child of thruaxels with rim brakes to support. Bike shops wouldn't stock it. Nobody would buy it.

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Calnago
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by Calnago

@AJS914: Look at a thin QR road skewer, which fits through a light hollow axle, the ends of which rest in the dropouts. Now look at a thick thru axle. Then consider that all the braking forces are on one side of the fork. Not sure how you can't see how the thru axle is going to help prevent twisting when the brake is applied. Of course, if the fork is beefed up enough that it can more than withstand any twisting effect, then so be it, no big deal. But that's the point, it has to be beefy enough to withstand that, and in the road bike genre, light weight counts.
Last edited by Calnago on Mon Nov 19, 2018 9:33 pm, edited 1 time in total.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

AJS914
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by AJS914

I'm talking about a thruaxel with rim brakes as the OP is suggesting.


TobinHatesYou
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Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

I’m faster to remove/replace wheels with TAs than QRs in practice because lawyer tabs prevent me from dropping out QR wheels without first loosening the skewers by a couple turns, and also if I don’t weigh down the bike when closing the skewer, there is some chance for it to get cocked at an angle.

With a TA I slide the wheel in place, no lawyer tabs and just screw the bolt in.

With a rear wheel there’s the additional annoyance of maneuvering the QR nut on the drive side inside the chain.

TA adapters on most modern hubs and trainers are just different endcaps. A notable exception is the Tacx Neo, which uses a poorly designed skewer and two loose insertss because the Neo’s axle isn’t large enough in diameter. I believe the Neo 2 uses the same adapter, but adds a reverse threaded insert for the drive side (one insert each for 1mm, 1.5mm and 1.75mm)

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Calnago
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by Calnago

AJS914 wrote:I'm talking about a thruaxel with rim brakes as the OP is suggesting.
Ah, then yes, with rim brakes it’s not going to matter, since the asymmetric braking force on one side isn’t there, so why not go with the lighter, quicker version. I’m not talking crazy light like some of these ti skewers but a good quality Campy or Shimano skewer. But whichever you prefer is just fine.
And yes, if you keep the lawyer tabs on your bike, than that completely negates the “quick” out of the “Quick Release”, hence all mine are filed off during the initial build. Nothing wrong with using thru axles on a rim brake bike, just as there’s nothing wrong with using a normal quick release skewer. On a disc bike however, the thru axle is essentially a necessity if dealing with a relatively lightweight fork.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

dvq
Posts: 157
Joined: Mon Sep 25, 2017 1:36 pm

by dvq

TobinHatesYou wrote:
Mon Nov 19, 2018 10:19 pm
I’m faster to remove/replace wheels with TAs than QRs in practice because lawyer tabs prevent me from dropping out QR wheels without first loosening the skewers by a couple turns, and also if I don’t weigh down the bike when closing the skewer, there is some chance for it to get cocked at an angle.

With a TA I slide the wheel in place, no lawyer tabs and just screw the bolt in.

With a rear wheel there’s the additional annoyance of maneuvering the QR nut on the drive side inside the chain.

TA adapters on most modern hubs and trainers are just different endcaps. A notable exception is the Tacx Neo, which uses a poorly designed skewer and two loose insertss because the Neo’s axle isn’t large enough in diameter. I believe the Neo 2 uses the same adapter, but adds a reverse threaded insert for the drive side (one insert each for 1mm, 1.5mm and 1.75mm)
I'm faster at swapping out wheels with my TA as well, but my bike also came with DT Swiss RWS TAs.

by Weenie


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