You are hereForums / By Discipline / Mountain (off road) / MTB Gear / Wheel issues...
Wheel issues...
Hi everyone
Really hoping someone can help me with this because I'm stuck, confused and frustrated 
I recently decided to go tubeless and invested in a Shimano XT 29er tubeless wheelset. I got Shimano RT67 rotors for them and successfully fitted up the tubeless tyres. All good, so far. All ready to try out my nice new tubeless wheelset and now the problem. I inserted the front wheel, but it will barely turn due to rubbing on the pads/rotor. I inserted the rear wheel and it turns perfectly. The original wheelset also turns absolutely fine. My assumption was that the new wheelset would simply "drop in" and be fine given that I haven't made any major changes between the wheelsets. Yes, the rotors are the same diameter (160mm) and both Shimano. The only difference being a small upgrade from RT53 to RT67 rotors. The caliper is unchanged (Shimano M446). The original wheels are a set of Alex rims laced to Shimano hubs (RM 66 for the front). The only thing I can think of is a possible warped rotor (ie: the original one). There is nothing visibly obvious when I look at the rotor, but late last year my LBS did a hub overhaul as part of a major service and afterwards said that they had slightly adjusted my caliper to stop some rubbing. I haven't yet adjusted the caliper with the new wheel fitted. Yes, this will fix the issue, but it will also mean the wheels aren't esily interchangeable. Am I missing something obvious or am I on the right track with it possibly being a warped rotor? Any thoughts/ideas much appreciated. With thanks.
- Login to post comments
- Bookmark & share
It may be slight tolerance differences in the hub where the disk bolts on.
It takes 10 seconds to adjust the caliper, so try that. Loosen the 2 bolts, spin wheel, grab brake and hold, retighten caliper bolts. If that fails, then its outside my experience.
!
If it is a warped disc the wheel should be free in one part of its rotation and tighten up in another part.
If the hub/rotor mount between the two wheels are even slightly different (from the centre line of the hub/wheel) then the rotor will rub the pad on one wheel if the calipers are adjusted for the other.
You could adjust this by shimming the rotor that runs closer to the centre line of the hub so the two are exactly the same distance (from the centre of the hub/wheel). But you will need thin shims. Given the tolerances between manufacturing runs of different components then it may be that the rotor on one wheel is farther out from the centre line of the hub. Only needs a few thou.
It isn't a huge problem to reset the calipers for each wheel but can be a pain if you change the wheels frequently. Not sure what your hub is like but it may be possible to adjust one hub so both rotors are in identical place.
HTH
Your pads may be worn unevenly, that is, one has worn down a lot more than the other. Or you may even have a sticky caliper. Set the calipers up with a new pair of pads, making the pistons are equal in their travel. When you've set that up, then try swapping your wheels in and out.
I've had the same problems with my crank brothers wheels and my race wheels.
Shimmed out the crank brothers set with a cut up coke can and no problems since.
Being shimano wheels, I'm going to guess that it's centerlock? If so, then won't be able to shim the rotors as far as I know. Just adjust the caliper. takes 10 sec with a 5mm allenkey.
Thanks for the thoughts and tips everyone. Yes, they are centre lock wheels so, as muvro said, shimming wont work. I'm thinking what oldernslower and others have referred to re: a slight difference between the wheels in terms of rotor position makes sense and that adjusting the caliper position is the answer. This doesn't help my issue with the interchangeability of the two wheelsets, but just something I will have to accept. Who knows, maybe all the extra traction and resulting confidence from the tubeless wheels will see my old wheelset relegated to the back of the shed
Thanks again everyone, much appreciated.
Also- I checked pad wear Zoom and they were nice and even with still plenty of meat. Will try caliper adjustment. Cheers
Stupid question, maybe.. but did you pop the pads out and use a spanner/tool to push the pistons back out, put the pads back in and try that???
If not, as others have said, just need to loosen the calliper, crank on the brakes to let it find a neutral position, then tighten.
Also... XT wheels are pretty good, not sure why you would want or need to be swapping wheels??
No, not a stupid question MrMez. Popping the pads out and re-inserting, combined with a slight adjustment of the caliper position did the trick
Re: your other point and XT wheels- I had visions of holding onto my original wheels to use in training or when trail conditions are less than optimal. The XT wheels I had in mind for events. Realistically though, I'll probably just end up riding the XT's all the time. I think that the weight difference and the performance advantage of the tubeless set-up will make it hard for me to go back to the original wheels. The wheels are for a hardtail and I'm hoping that the lower pressures of the tubeless set-up will result in much better traction and handling. Thanks again to all for thoughts/suggestions.
Perhaps post mount discs are different, but AFAIK it's generally applicable that disc calipers should be centred to the rotors rather than relying on the pistons to operate equally. This maximises the power, but it may require a few attempts at resetting the pistons with the pads out to prevent rotor rub on the pads. Check out the Hope video on their site if I've not been clear.
Differences between hubs are normal, I have to reset my calipers if I change between my 3 wheelsets, 2 of which are even from the same manufacturer but with different hub models. The space left between the rotors and pads is probably less than 1 mm either side so the system is fairly sensitive to manufacturing tolerances.
The info re hub differences is really helpful Jeronimo. I had been tackling the issue with the mistaken belief that there was some sort of industry standard when it comes to wheel dimensions and hub/rotor placement. My learning continues
I have exactly the same problem on my downhill bike. I have two wheelsets with the same hubs that were purhcased at the same time and there is a very slight rubbing when I change wheels. THe disks are perfectly straight.
My guess is that there is a very slight difference in hubs. No problems I just loosen off the calliper bolts and readjust the brakes. Doesnt take long at all.
Yep, had exactly same issue as OP, with same wheels - XT-29. Decided easiest thing to do was just stick with the new wheels for everything, rather than the original plan of swapping between wheelsets.
It's a beatch, but there are 3 or 4 tight tolerance components between the drop out and the pad.... Even with the same brand components there's likely to be some minor variance in fit.
If you want to be really dedicated to interchangability (read "anal") you could do the swap of rotors and axle end caps between hubs until you hopefully find a perfect interchangable set up. 2 or 3 hours effort should see you saving that 30 seconds every wheel swap
I'm hearing you Slowpup! I think I've spent enough time agonising over this already. With the info and thoughts of you and others, I'm reassured that I wasn't losing the plot and missing something really obvious. With the understanding of there being tight tolerances and slight variations between components, I'm all ok about sticking with the one wheelset and putting more of my precious time into actually riding
Forgot to mention, even slight differences in QR tightness can cause rubbing. They don't need to be so tight it hurts your hand to close them, but nor should they close too easily. Sometimes this slight adjustment is all you need, but it should be sorted properly via the calipers otherwise.