AASQ #155: Why can’t I have a road bike with rim brakes and thru-axle wheels?

We know, there’s no such thing as a stupid question. But there are some questions you might not want to ask your local shop or riding buddies. AASQ is our weekly series where we get to the bottom of your questions – serious or otherwise. Hit the link at the bottom of the post to submit your own question.

This week we’re turing our attention to the asphalt, looking at why road bikes with rim brakes and thru-axle wheels are a rather uncommon sight. To tackle the question, we have experts from Felt Bicycles and Argonaut Cycles. They are:

Why can’t I have a road bike with rim brakes AND thru axle wheels?

Felt: Another way to consider this question would be to ask, “Why do road bikes have disc brakes and thru-axles”? There is no technical reason why they could not have rim brakes and thru-axles or, alternatively, disc brakes and quick releases. Disc brakes with quick releases were utilized on mountain bikes for quite a few years. The push for disc brakes on road bikes came around the same time that mountain bikes were moving away from quick releases and to the 142×12 thru-axle standard. Thru-axles were developed for mountain bikes, as quick releases did not offer a stiff enough interface between the wheel and frame, especially on full-suspension mountain bikes.

felt vr carbon thru axle dropouts flat mount disc brake caliper

Thru-axle dropouts and flat mount brake caliper on the rear end of the Felt VR Carbon Road Bike

Road bikes traditionally used 130 OLD (the distance between the inside faces of the dropouts, sometimes referred to as “spacing”) quick release hubs, while mountain bikes had used 135 quick release hubs. While there were some rare 130 disc hubs that were made for some early disc road and cyclocross bikes, they were not ideal. Because the disc brake mounting flange occupies a substantial area, the spoke flange has to move towards the center of the hub, which decreases the spoke angle and the strength of the wheel. The 135 OLD width hubs are wide enough to support a disc brake flange and still maintain acceptable spoke angles. (Note that 142×12 is the same 135 OLD width hub with different end caps for thru-axles.)

Road bikes could have moved to 135 quick release hubs, but because mountain bikes were already moving to thru-axles and all of the manufacturers were gearing up for that, we got 142×12 as the standard for all road and cyclocross bikes. While wheel changes aren’t quite as fast with thru-axles, they offer a much more robust connection between the frame and wheel.

felt vr advanced road bike review riding action

So, back to the original question. “Why can’t I have a road bike with rim brakes and thru-axle wheels?” As I explained above, it is partially about timing and functionality. The timing part is that the push of disc brake-equipped road bikes came at a time when mountain bikes had, for the most part, moved to 142×12. Because it was an existing functional standard it was just adopted for disc brake-equipped road bikes. The functionality issue is that thru-axles never offered a significant enough advantage for road bikes on their own to cause the industry to move to it. The change had to come along with disc brakes as the primary driver.

Argonaut: From a performance standpoint there’s no reason you can’t run a thru-axle on a rim brake bike. It’s not like the axle interface would impede rim braking performance. In fact, it would likely be a big improvement.

argonaut disc road bike rear thru-axle disc brake mount

Thru-axle dropouts on the Argonaut Disc Road Bike

But, no one makes a thru-axle, rim brake hub, that I know of anyway. I’m not sure if DT-Swiss end caps are swappable between their TA disc hubs and rim brake hubs, but I don’t think so. That being said, I can’t think of a reason you couldn’t build up a rim brake rim around a disc brake hub. You would have a rotor interface hanging out not being used that would be a little weird, but that would hurt anything.

You’d need a custom fork, though, maybe Wound Up would make one for you? The rear spacing is easier, but again, you’d need a custom frame that could take a 142mm x 12mm thru-axle. I bet Aaron at Mosaic would build you one! Haha. Where there’s a will, there’s always a way.

argonaut disc road bike thru-axle wheels

Got a question of your own? Click here to use the Ask A Stupid Question form to submit questions on any cycling-related topic of your choice, and we’ll get the experts to answer them for you!

Subscribe
Notify of
guest

This site uses Akismet to reduce spam. Learn how your comment data is processed.

26 Comments
Oldest
Newest Most Voted
Inline Feedbacks
View all comments
peter
9 months ago

I believe Chris Bishop had a thru axle rim bike at Philly.

Shawn Yackle
Shawn Yackle
9 months ago
Reply to  peter

Mars Cycles actually

Bob
Bob
9 months ago
Reply to  Shawn Yackle

Yep, with White Industries hubs…

Czechmate
Czechmate
9 months ago

I like to answer « stupid » questions with another « stupid » question.
In this case, the one that comes to mind is: « Can I have my cake and eat it too? »

Dan
Dan
9 months ago
Reply to  Czechmate

Thanks for proving the old adage. There are no stupid questions only stupid answers.

Czechmate
Czechmate
9 months ago
Reply to  Dan

As far as proving old adages goes, I’m but a mere shadow next to you.

Jburns
Jburns
9 months ago
Reply to  Czechmate

Yes. If you you in the US.

Tristan
9 months ago

All DT Swiss 130mm and 135mm non-disc hubs use the same shell, axle, and driveside endcap so converting a 130mm non-disc hub to a 142x12mm is no problem.

Left side:  Fit HWA00100S2193C
Right side:  Fit whatever endcap matches your freehub body. HWA00100S2192C for HG mountain, HWA00100S3525C for HG road, HWAXXX00S8124S for XDR, HWAXXX00S3188S for XD, HWAXXX00S0491S for microspline.  You could do Campagnolo and N3W as well but I don’t have those codes to hand.

ranggapanji
ranggapanji
9 months ago
Reply to  Tristan

to add to the discussion, I’ve installed QR endcaps from old 240 hub to DT Swiss 240 EXP Centerlock hub to make an XDR compatible hub with 135mm spacing. need to machine down the driveside endcap flange to make it fit the freehub body, but it snaps right in.

john v
9 months ago

That’s where custom steel/ti, whatever comes into play. The frame with thru-axle and rim brakes, piece of cake. It’s the fork that matters. A custom frame builder could build a custom fork, but it would not be carbon, really just ti or steel. The hubs would be interesting, thru axle without disc mount? Hmm. Centerlock hubs would look better than 6 bolt I suppose. I often go down these rabbit holes of what if, but then quickly realize it’s just not worth the hassle and money, and go with stock stuff like everyone else.

satanas
satanas
9 months ago

The real question is not “why couldn’t you,” but rather why would you bother making something with limited interchangeability deliberately – if you’re not a large bike industry player.

Brian
9 months ago

Just a ‘heads up’ for Jeremiah Smith regarding his ‘outdated claim’ that reducing spoke angle decreases the strength of the wheel. I refer you to
USA Patent US 10,710,398 B2 Titled: “A Bicycle wheel hub, a bicycle wheel, a bicycle, a method for making a bicycle wheel and a method of making a bicycle” which uses a prestressed cable / strand structural model for the bicycle wheel and the published data in the Tables attached to the Patent. Thanks

Dan
Dan
9 months ago
Reply to  Brian

Hi, can you explain how your invention makes that claim outdated? Seems your invention preserves the spoke angles are preserved due to massive diameter hub flanges, but I question the durability and stiffness of the hub flange material. I also worry that the flange acts as a big lever for lateral force, which affects the tolerance stack of the bearing seat, bearing, axle, pawls, etc.

Jon
Jon
9 months ago
Reply to  Brian

The tables for that patent appear to show that increasing the flange separation also increases lateral strength. The fact that sales of your product are restricted to TT applications would suggest to me that you are not targeting any markets in which lateral strength is particularly important.

Alum
Alum
9 months ago

I’m not sure a thru axle is even a good idea.
They have a significantly lower clamping force than QR and because they’re not positively clamped by the frame, I don’t think they improve stiffness either.

They’re better from a safety point of view to prevent a wheel from moving inside or even falling out of a dropout. But that’s about the only benefit.

So the better question is whether you’d even want a thru axle rim brake setup at all?

Fern
Fern
9 months ago
Reply to  Alum

Thru axles were invented for mountain bikes because they were getting a lot of disc brake rub with quick release, and some accidental front wheel pop-out because of braking forces. They are much more stiffer.

Alum
Alum
9 months ago
Reply to  Fern

I don’t think you can definitively say that the thru axle was the main driver.

I remember those days well – but everything was less stiff. Forks in particular. Remember how skinny dropouts were back then.

Don’t forget also that the thru axle works only in tension. The hub has its own axle. The interface between the hub axle/endcap and dropout is what creates the stiffness. Not the thrus axle itself.

whatever
whatever
9 months ago
Reply to  Alum

Ahhh, not losing a wheel is kinda important. But I guess not being injured isn’t important to you, or you like pain.

But then there is the fact that the wheel inserts the same way every time in the same positio0n (hello, less chance of brake rub).

syborg
syborg
9 months ago

These answers were basically because no one makes a rim brake bike with TAs

As Ben Farver said that rim brakes with a TA “would likely be a big improvement.”

So the real question is: why doesn’t anyone make a rim brake bike with TA?

Don’t give me no nonsense about no one makes hubs for this config. Before disc brakes no one made TA hub. There is absolutely no technical reason to prevent manufacturing a TA rim brake hub.

David
David
9 months ago

It’s kind of annoying not knowing how much longer rim brakes and quick release hubs will be available for, I’d love to invest in a new ti frame and use all the kit that I’ve got already (Chris King bits, Ultegra etc). But I’m worried I’ll spend £2k on a frame and then only be able to get parts for another couple of years for a frame that should really see me out.

Antoine
Antoine
9 months ago
Reply to  David

You should not worry really. Contrary to popular forum belief rim brakes are here to stay. Lower end bike will continue to use those. Also I had no problems keeping a 40 year old bike in functioning order so you should not worry about 2yo tech.
What should be avoided for the long run are useless gimmicks like axs and even to some degree di2. Anything electronic will hurt maintainability if you aim to keep your rude more than 10years.

Dinger
Dinger
9 months ago
Reply to  David

How often do you wear out hubs? Buy good ones and take good care of them and they’ll likely outlive you.

There is a risk of obsolete cassette interface but even that is probably still a long way off.

Collin S
Collin S
9 months ago

@feltbikes. Quote “Road bikes could have moved to 135 quick release hubs, but because mountain bikes were already moving to thru-axles and all of the manufacturers were gearing up for that, we got 142×12”

But they did do 135 qr. Heck, I have a felt cx bike with disc and quick releases.

David Hunter
David Hunter
9 months ago
Reply to  Collin S

That was the CX standard for a very brief interval, but that’s still not a road bike.

Stuart D
Stuart D
9 months ago
Reply to  Collin S

I have a 2017 Tarmac wirk post mount disk brakes and QR hubs. Works ok

BCManUCD
BCManUCD
9 months ago

“Why can’t I have a road bike with inferior braking performance AND slower wheel changes?”