I have a 2022 Specialized Diverge with with SRAM Rival hydraulic disc brakes and I have tried changing the front pads around 10 months ago after around 5000 miles and just tried changing the read pads at 10,000 miles.
I basically follow this: https://www.youtube.com/watch?v=xTGHdFt5Y-s but both times I have had issues with the caliper pistons not retracting properly after replacing the pads.
I basically remove the wheel, use the park tool PP-1.2 Hydraulic Brake Piston Press https://www.parktool.com/en-us/product/hydraulic-brake-piston-press-pp-1-2 to retract the caliper pistons, remove the caliper spreader retaining pin, put the new pads in the spreader and reinstall.
Before I use the brakes I make sure the wheel spins freely without the rotor making any contact with the pads, test the brakes to make sure they appear to work okay, take the bike outside and get up to speed and use the brakes to slow down to 1-2 mph, repeating 10 or so times.
Both times the rotor ends up still rubbing the pads, I even loosen the caliper retaining bolts, apply the brake and tighten the bolts while keep the brake lever squeezed to try and align the caliper correctly but it never helps.
Last time I messed around too much and ended up advancing the pistons out too far with no pads installed to try and clean the pistons to make sure there was no gunk preventing them from moving in and out properly so I took it to a shop and they had to replace the caliper, changed the pads and did a brake bleed.
This time after running into the same problem after changing the rear pads I just decided to take it into the shop but would like to know what I am doing wrong. Am I screwing up by not using a "pad spacer" they mention in the video at the 4:45 mark?
by BruceA78
2 Comments
One step that I’ve added is to open the bleed port at the lever side before pushing the pistons back into the caliper.
Brake lines can become over-pressurized in when resetting pistons. This can lead to pistons not fully retracting and/or damage to any diaphragm or seal that may be in the fluid reservoir.
You will often get some fluid ‘burping’ from the open lever end bleed port when you reset the pistons. It should only be a couple drops, and shouldn’t require a full bleed before reinstalling the bleed port screw. Adding a few drops of fluid to the port before closing it should minimize air getting in.
Attaching a bleed cup or syringe with some fluid in it to the lever port before pushing the pistons in should prevent any air from going into the lever if you are worried about it.
You’re not really doing anything wrong. At the end of the day, SRAM brakes just plain have sticky/uneven piston retraction issues a lot.
Buried in the troubleshooting steps for your brake, you’ll find a procedure for using the pad spacer (the thin one, not a bleed spacer) for helping to get them to extend and retract more evenly. Try that.