After having crashed, I had to purchase new wheels.
So I bought my first pair of deep-ish (50 mm) carbon wheels. They work fine, but when I get out of the saddle and stand on the pedals, there is a terrible scraping noise and feeling when I push down the left crank with high torque. Does anyone know what could be the cause of it (poor tire fit, broken frame, bottom bracket…)?
Thanks in advance
Brake rub?
My disc wheels will rub the front wheel unless they are adjusted perfectly even with my meager 700W max power output.
But I have rim brakes
The tire/wheel can still rub the brakes on rim brakes when the wheel flexes. Or on older bikes the tires can rub on the stays if they are too wide. On my 2011 Cervelo R3 I can only run 23’s on the rear or they rub against the stay right above the brake caliper.
Why do you think this is related to the wheels?
It sounds like you crashed and replaced your wheels - have you checked out everything else on the bike for damage? Does the noise happen when you use a different front wheel? Rear wheel?
My bike makes the same noise and I can’t figure out where the hell it’s coming from.
Is the width of the new wheels wider than the old wheels? If so the tire will probably be a different shape.
A photo of the tire clearance under the brake bridges, and tire clearance at the chain stays and fork crown would help out.
This is interesting about wheel stiffness Debunking Wheel Stiffness - Slowtwitch.com
Rim brakes can have brake rub, too.
Because that’s a common issue when applying lots of torque by going out of the saddle, and it is the component that has changed. Flex in the wheel and the hub (the latter is sometimes neglected in the equation) can cause rub between e. g. the tires and the rim brakes. Especially if the new tires are wider than 25–26 mm, that is not unlikely. (AFAIK most road bike rim brakes max out at 28 mm.)
I know they are new wheels so this is not as likely the cause, but I’ve had that problem when my read hub bearings were old and grinding on an MTB. I read that cleaning your bike with Muck Off can strip the bearings and the problem started for me right after using it to clean my bike. It sounds just like tire rub + a little extra grinding.
My point wasn’t that the wheels weren’t a possible culprit - but that he has already narrowed the problem down to the wheels without providing enough information (in my opinion) to justify removing lots of other potential sources. Maybe he’s already done that (in this case - really easy to test - put another set of wheels on there and see if you can duplicate the noise) and just didn’t tell us - but that should really be the first step
In general we all tend to identify what we think is causing the noise and focus on that without considering other possibilities. Maybe it is the wheels, maybe he has damaged his chain stay in the crash and the new wheels are just an innocent bystander, maybe a million other things…
I just put together a cannondale CAAD13 rim brake bike. Brakes are the newest Ultegra direct mount.
Front wheel is a Reynolds SDV66 (narrow rim), rear wheel is a zipp 404 firecrest (wide rim).
Tires are Specialized Turbo non cotton, 28mm, measured 30-31mm at 80psi.
Vertical clearance under the brake bridge is a lot, maybe almost a cm. But side to side clearance is less because of the brake mounts and the metal around the the bolt that the brakes mount to. Maybe 4mm to each side of the brakes.
I can rub either wheel against the brakes if I sprint. It’s annoying and I will probably try to find a 28 that is actually a 28 and not a 31 when measured and inflated.
I haven’t tried it with other wheels yet. Exept for some scratches, there is no visible damage. I also don’t notice anything when I use it on my indoor trainer. (It is an aluminium bike by the way)
I’d definitely give it a try with a different wheelset, just to confirm the source of the noise
Deep carbon rims flex more than other rim type’s especially any aluminum rim. Id open up the brakes and see if that helps.