I have a Cannondale Topstone with a GRX 810 rear brake.
I just pulled my rear caliper off and noticed the two bolts are different. Are they both supposed to have that nub on them? Or just one?
Also the bolt with the nub on it has a metric head. Whereas the one with the flat end is torx. I kind of think when the bike shop assembled my bike they lost a bolt and used a random spare.
Potentially related: the rear brake constantly squeals. It’s not contaminated bc I’ve checked the pistons for leakage, and changed the pads and rotors. Could it be due to the bolts?
by Roman_willie
3 Comments
Yes. The one with the pin head tip is for the side with the retaining clip.
yes, thats a place for a locking pin thingy. i usually see it on the rear brake.
A relief like that at the end of the bolt is usually for a c-clip. I think the bolt has plenty of strength on its own, but insurance with a clip or thread locker can’t hurt.
Squealing can come from several things.
– I would only suspect the mounting bolts if they were loose.
– It could be from contamination, certainly, and you can resurface the pads and rotors with sandpaper and isopropyl — don’t always need to be replaced. You should also clean out the inside of the caliper while you’re at it
Given that you’ve replaced them, it’s more likely that:
– the caliper is at an angle to the rotor: squeeze the brakes, and see if it stays straight or twists
– loose rotor, loose axle mount, or loose hub. Check your rotor lock-down bolts, and the drop-outs to see if your axle is moving. Most likely is loose hub: pinch your rim, and wiggle it in-and-out of the frame. Any movement or clicking means the rotor is unstable while you’re braking.
– I suppose there’s a possibility there’s some gunk behind the pads