I recently built a bike with a used Cube frame from eBay, and an Ultegra hydraulic groupset (also used but very little).
Everything is lovely but when I set it up the rear caliper would lean onto the rotor when I tightened the screws. My bike shop have faced the mount point on the frame so the caliper now tightens without touching the rotor, but it’s still very close on one side. It’s clearly offset against the rotor.
It’s cycleable but I’m worried it will unevenly wear the pads, and as soon as the bike gets slightly wet the rear break makes a sort of grinding sound while riding (not braking, just riding).
I’m just wondering if there’s any way to centre the caliper properly. Some sort of shim? Or should I get it faced more? Or is it likely just a frame issue?
by jevawin
12 Comments
This could probably be due to an error when screwing the wheel in, check if you could put an extra small washer to push the wheel slightly to the right.
Ignire that goofy nonsense about putting washers in the wheel. Your caliper is misaligned, but the mount is designed to have some adjustment in it. Loosen the caliper mounting bolts so the caliper can wiggle, then pull the brake lever, while holding the lever retighten the caliper mounting bolts.
Just hold the caliper a little bit over while you tighten the bolt. The whole “hold the brake while you tighten” is good for most brakes getting centered but sometimes you need to manually align it instead. Just use your hands.
I saw a video where they undo the bolts, put a piece of thin cardboard on the close side, held the brake lever and did up the bolts. Might be worth a go?
Your drive side piston is pushed out more; have you checked how freely moving the non drive side is?
Sometimes it seems like calipers just want to act up, and like you said, will just pull itself back to the starting position when tightened down.
If my caliper does something like that I use a temporary shim to ‘force’ it to stay aligned in the center of the disc. You can use a shim like [https://www.birzman.com/products_2.php?uID=2&cID=4&Key=133](https://www.birzman.com/products_2.php?uID=2&cID=4&Key=133) for that. I have used an old creditcard for this which worked – or you can fold a couple of papers out of a note book and put that over your disc.
With your shim in the caliper, hold down on the brakes like before, and tighten the bolts.
Make sure the rotor is torqued and make sure the wheel is dished properly. Then make sure the both pistons move, then make sure the caliper is centered on the rotor. Many ways to do these things but that is what needs to happen
The brake pistons need to be reset.
Take the brake caliper off then spread the pads as wide as possible. The tool I use for this is The Park Tool PP 1.2 (hydraulic brake piston press) but I suppose you could use a large flathead screwdriver or perhaps the handle of a spoon. Just try not to damage the pads’ braking surface.
The goal is to get it so that the pistons (the part that contacts the brake pads metal backing plate) are no longer visible. It may require a little force but not too much. If you are having trouble you could take the pads out and push on the pistons directly to get them to back off before reinstalling the pads.
Once this is done, bolt the brake caliper back on but don’t tighten it all the way, just leave it a little loose so it can still move side to side. Then pump the brake lever a few times. Initially it will feel way too loose but after a few pumps it should achieve the desired amount of reach.
Finally, hold the brake lever tight then do the bolts up all the way – not super tight though. That should get the caliper into the right position. Depending on the quality of frame and facing there may still be a little brake rub which you can try to improve but this process should essentially resolve your issue.
Good luck
Never gonna fix this, you aren’t a mechanic. might as well post a picture of your cars engine asking why it makes noise
Are you resetting the pistons when centering the brake? This is done with the wheel out and pads in. Use a large and clean flat blade screw driver, wedge between the pads and wiggle it side to side to gain some clearance. Don’t be too aggressive with spreading the pads because it can cause problems with your lever’s bladder.
When centering flat mounts I don’t use the loosen the bolts and pull the lever method. I eyeball it and very very gently tighten the caliper bolts, alternating between them.
I’m my opinion your problem is now a lazy piston. There are ways to resolve that problem. And you might just need to replace the caliper and have the shop do a bleed.
I think you need to reset the pistons. I’d also recommend cleaning and lubing them while you’re at it.
Time for a new bike.