Installed Shimano XT four pots last weekend. I went to bed them in this weekend and they had absolutely zero bite. Brakes were bled after install and re-bled after the first failed bedding in. No air or anything in the system. Levers feel good and have solid action with no sponginess.
After the first attempt to bed them with no luck, I inspected the pads and saw they were discolored. So I sanded that away, cleaned the rotors with IPA and tried again—still no dice.
My only thought is contamination? Both the front and rear brakes have the same issue. I was incredibly careful during install, wearing rubber gloves and all that. Perhaps they were mucked up in shipping (they were a OEM set repackaged for resale at a discount from Planet Cyclery).
Photo is after they were sanded and I tried to bed them a second time. They turned the same color as the first attempt.
by Apolloscreed13
2 Comments
Are you sure you used the correct bleed block?
So start by completely cleaning the caliper with isopropyl alcohol.
Then sand the pads.
DISCLAIMER. If they’re N03A and they’ve become contaminated it’s super difficult/often impossible to clean up resin/organic pads effectively. If they’re N04C, the metallic compounds are definitely more possible to clean up if they’ve absorbed oil but still very difficult and often not worth the effort IMO.
Then clean the rotor with isopropyl alcohol and a light sanding.
Proceed to bed in the brakes as per usual, light incline moderate braking 10-15 times until they bite effectively.
If all else fails you may have a leaky seal behind one of the pistons, a leaky caliper from somewhere else, or possibly they’re getting environmental contamination from where you’re storing it.
We had a guy that had a little DIY wood shop about 10m from where he stored his bikes and some sort of spray on oil he was using would contaminate his brakes every time he used it and it took him forever to figure it out.