Disc Brake Wheel Change

I am currently researching to buy a brand new bike for myself for the 2021 season. I have almost accepted that this bike will be a disc brake model. Would be great to get some feedback from the community on here before I pull the trigger on how a wheel change would work in a race scenario.

  • I know that for my MTB there is a thru axle and this needs an Allen key - surely a road bike should have a QR thru axle for a quick wheel swap in the event of a mechanical or puncture?
  • And following on from that - is there ever an issue around caliper alignment when you swap out a disc wheel? Getting rim brakes aligned is one thing but discs seem more unforgiving.

And for what it’s worth I’m looking at the ROSE X-Lite Six, Vitus Vitesse Evo, Scott Addict RC or Giant TCR. One of these days I will make my mind up :slightly_smiling_face:

If you watch the Tour, you will see mechanics using electric keys to quickly remove the through axles. No, they are not quick release.

I had this on the MTB. there are shims for the disks so things can align correctly between wheelsets.

I don’t think most bikes come with QR thru axles but I believe there are companies that sell ones that you can buy.

Yes, disc spacing from the wheel can vary a bit from wheel to wheel. You can buy little shims so that you can align your discs the same if you have multiple wheelsets. But if you forsee taking a wheel from a neutral support in a race then yeah you might run into a rubbing issue

They do make “quick release” style TA though…

Regardless, most of the time this isn’t going to be an issue, as you’re not going to be in a TdF style situation where you need a lightning fast wheel change.

To your second question, I’m not entirely sure, as I don’t have a ton of experience with disc bikes, but as long as everything is installed properly and is in good working order, there shouldn’t be any issues when you’re changing wheels. @jeremy is someone that would know more about this topic than myself though.

  • As already covered above, there CAN be issues with disc to rotor alignment. The spacing in side the caliper pads is quite narrow, and the tolerances on wheels and disc mounts leads to possible alignment issues.

  • Also as covered, it is possible to make a mix of 1 bike with multiple wheels “work”. But it takes careful analysis of the wheels and actual disc location, proper caliper placement, and all that in consideration of which wheel(s) need to have the shims installed, to shift the disc to an aligned position. This matters, because you can only shim the disc in one direction. So you need to select the for the caliper alignment carefully in order to allow shimming for the other wheels to match.

  • As with rear wheels and related cassette / rear derailleur alignment, sometimes you get lucky and everything matches. But often, they will not and you need to resort to shimming and careful caliper setup for “trouble free” swaps. Even with that, you can still suffer from slight rub issues due to the close tolerances between discs and pads.

2 Likes

Thanks for the responses guys. I race in Ireland and traditionally all of our teams have support cars with spares. I’ve punctured a handful of times in races and always managed to get paced back on to the peloton after a swift (rim-brake) wheel change.

Just want to make sure that with discs my race won’t immediately be over.

What I might do is buy a backup set of disc wheels from the exact same brand (maybe different depth) to make sure no alignment issues, but no way I’m fiddling around with an Allen key on the side of the road as the bunch speeds away!

1 Like

I’m not sure why you say “accepted a disc bike purchase”
There is increasing chatter about disc brake modulation. On a Mtb. Where your riding on dirt , not slick pavement , knobs to help with braking and typically slower speeds disc are a no brainer.
On a road bike with much narrower tire contact a slicker surface and a weight penalty For A disc brake bike , I’m not sure you should be accepting the need for a disc bike.
I’d also add That the position Of rider and Brake levers on a mtb. Bar is a far better arrangement For even modulation of the brakes, seems much more ergonomic to me, compared to the rider And lever position of rider and lever on a road bike. I certainly feel more comfortable on my Mtb. Bike over my road bike . Yes my road bike is rim brake , Yes they are Carbon, with a carbon brake track, Yes , I ride in the mountains and fly down hill.
In the Tour, that rainy Multiple rider crash day and all the crashes in general was blamed on slick road Etc. but perhaps the disc modulation played a part also.
Also , On one hand we pay 1,500 dollars for Dura Ace over Ultegra and it’s touted as lighter and worth the extra money and the next year they try to sell us a bike That is heavier and tell us that’s worth while .
I’m not saying don’t buy a disc bike, I’m a light weight rider , I want to be on a light bike.Consider what you want ,not what the bike industry is telling you that you need.

Discs on a new wheel - even the same wheel - may not be a perfect fit for your calipers. There is extremely small clearance so a tiny difference can cause a lot of rub.

The key is testing it before hand to workout any issue and then you can be sure it will slide in and work when the pressure time comes.

1 Like

I know they exist. My MTBs have them. Just what I have seen. That and $10 USD might get you a cup of coffee somewhere.

On-topic: I recently go a second, aero wheelset for my gravel bike. With 0.25mm shims centerlock disc shims available from NovemberBicycles.com, I’ve gotten the discs to align such that I can swap the wheelsets without need for caliper adjustments. To my surprise, this only required one shim on the rear hub, despite the wheels having totally different hub sets (Bontrager on the stock gravel wheels and DT Swiss on the new setup).

Off-topic: I feel like disc alignment has been an issue in the Tour this year. Multiple times, its looked like riders flatted and then were unable to continue just by replacing the wheel, either from the team car or neutral support. The most reliable solution has been a whole bike swap, which is often not possible for riders other than team leaders. I’m surprised I haven’t seen more discussion of this. The riders definitely appear frustrated, standing by the side of the road!

2 Likes

I can’t be sure but I don’t think this is an issue with disc-alignment but rather just the slightly extra time it takes to swap a disc wheel. So instead of a wheel swap they go for a whole bike swap. I think a lot of the extra time comes from the fact that without a QR lever the rider cannot remove the wheel themselves before the team car gets to them so the mechanic has to do the whole process themselves.

Definitely a possibility. Surprised that, at least in the front, they aren’t running axles with levers (at least the hidden ones, to keep them out of the wind). I guess with the weight of modern aero-allrounder bikes every gram matters to counteract added frameset and brake system weight.

There can be an issue. However, for the most part this is solved by a simple procedure. Use a tire lever to press the pads/pistons apart, and further back into the caliper. After the new wheel is in, simply depress the brake lever for that wheel a time or two to “self center” the pads onto the rotor position for that wheel. Barring some severe misalignment between the two wheelsets, this will almost always take care of the minor differences between two wheelset/rotor combinations.

1 Like

That pad reset is a very good point and part to add to the process. Can help in some cases, but won’t fix all problems, unfortunately.

1 Like

It sounded to me like the OP was worried about the alignment during a mid race wheel swap. So while this definitely would work it isn’t something I would want to be messing with while my group is riding away from me.

1 Like

My bikes all came with thru-axles that don’t need an allen key (they have a QR style lever). I’m sure you can buy those on ebay etc.

Regarding caliper alignment - I do swap the wheels on my cx bikes quite often. They sometimes rub a bit, but in a race I don’t actually notice. It might be different on the road, but even though it is annoying and might costs you a few W, it’s definitively still ridable.

Valid point! And to further your point, unless you always carry a tire lever in your jersey pocket (as opposed to spare kit/saddle bag), I’m not sure it could ever be done quickly, or that there is another solution for quick wheel changes.

There are indeed moments that I wish I had the simplicity of a rim brake bike, especially with regard to the caliper spacing and bleeding. However, then I get caught in a severe rain storm and remember that I’m a bigger rider…

This definitely doesn’t always work. It’s a good tactic to try but I’ve had all sorts of issues with getting the rub to go away completely.

Focus RAT thru axles are 1/4 turn release - as long as you keep them clean and lubed they are great.
I had them on my Focus Mares CX bike which took 3 years of absolute abuse without any issues (sold it as stopped riding CX).

https://www.focus-bikes.com/gb_en/rat#!

I thought they had licensed them to Merida a while ago on some models but it may have been another brand.

As for wheel sets, I had 3 sets of DT Swiss rims with the same model Shimano discs and they were all really well aligned, no faff between wheel changes at all unless you bent a rotor.

1 Like

When I was having problems with the front wheel on my previous bike (a TCR which had Ultegra hydraulic discs) I borrowed a front wheel for a few days from the LBS (was off a Scott, I think). There was very slight rotor rub, but it was rideable.

I wasn’t a huge fan of the TCR, incidentally; I thought it was a bit skittish and harsh. But it was certainly quick and you’re actually racing, so it might well suit you better than me.