Juvecu Posted December 12, 2009 Share Posted December 12, 2009 I have a 1998 Yamaha SR125 Custom that just failed MOT (roadworthy test) because the front brakes are binding. The front calliper was extremely dirty, I removed it, disassembled it, cleaned it well and put it back together. The brake pads are getting stuck to the metal shims each side and this seems to be the cause of the trouble. From memory I recall that brake pads normally move easily and that the fit isn't particularly tight where the shims are. The shims aren't bent/warped/damaged/badly worn at all, in fact, they look like they are in fairly good condition. I spent 30 minutes searching the internet and I haven't been able to find a place that I can buy the shims from. The question I'm faced with is whether replacing only the brake pads is likely to resolve the issue or not? I'd appreciate any input from anyone familiar with these things. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted December 12, 2009 Moderator Share Posted December 12, 2009 make sure that the brake pads are free to move and you may have to lightly scrape out any old and hardened brake dust to allow this to happen. Also how many pistons are there in the caliper, if its only one then it will be a sliding caliper and you need to see that it is free to do this. Link to comment Share on other sites More sharing options...
Juvecu Posted December 12, 2009 Author Share Posted December 12, 2009 I cleaned all the dust out so I can rule that out as a problem. It has 2 pistons, one is a little smaller in diameter than the other. I guess it is possible to have brake pads that are so badly manufactured that they don't fit like they should? Link to comment Share on other sites More sharing options...
mike1949 Posted December 12, 2009 Share Posted December 12, 2009 I have a 1998 Yamaha SR125 Custom that just failed MOT (roadworthy test) because the front brakes are binding. The front calliper was extremely dirty, I removed it, disassembled it, cleaned it well and put it back together. The brake pads are getting stuck to the metal shims each side and this seems to be the cause of the trouble. From memory I recall that brake pads normally move easily and that the fit isn't particularly tight where the shims are. The shims aren't bent/warped/damaged/badly worn at all, in fact, they look like they are in fairly good condition. I spent 30 minutes searching the internet and I haven't been able to find a place that I can buy the shims from. The question I'm faced with is whether replacing only the brake pads is likely to resolve the issue or not? I'd appreciate any input from anyone familiar with these things. I don't know if this is the same problem as I had about a year ago on a different bike, but my front brakes kept binding after I applied them, the problem was solved by changing the brake fluid and piston seals, Link to comment Share on other sites More sharing options...
Juvecu Posted December 12, 2009 Author Share Posted December 12, 2009 I've changed the brake fluid, I think I'll probably change the seals while I have it off. Just wondering about the binding between the shims and the pads, does anyone know how to get hold of the shims, do they sell separate or do you have to buy some kit? Link to comment Share on other sites More sharing options...
mike1949 Posted December 12, 2009 Share Posted December 12, 2009 I think I'll probably change the seals while I have it off. I've been trying that for years with the missus, and believe me it doesn't work. Seriously though, don't you put something like copperslip between the shim and brake pad? Link to comment Share on other sites More sharing options...
2 Wheels Posted December 12, 2009 Share Posted December 12, 2009 The shims (anti rattle shims) are there to stop the brake pads from jumping arround when the brake is not being applied. They are supposed to be pushed up tight to the pads. Need more info as to what appens when the brake leaver is let go,,, is it that the pads dont let go of the disks? Link to comment Share on other sites More sharing options...
Juvecu Posted December 12, 2009 Author Share Posted December 12, 2009 The pads don't let go of the disk enough to let the wheel move as free as it should. They seem to be stuck on the shims as opposed to behind held there by the pistons. Copper grease seems like something I could try, I think I have a tube lying around the garage somewhere... Link to comment Share on other sites More sharing options...
2 Wheels Posted December 12, 2009 Share Posted December 12, 2009 The pads don't let go of the disk enough to let the wheel move as free as it should. They seem to be stuck on the shims as opposed to behind held there by the pistons. Copper grease seems like something I could try, I think I have a tube lying around the garage somewhere... Piston comes back, shims and pads dont? Are pads really worn down? The shims havent been swaped from one side to the other as they have certin sides to go in (left+right). By all means put the copper grease between them. Link to comment Share on other sites More sharing options...
Juvecu Posted December 13, 2009 Author Share Posted December 13, 2009 The pads have some life left in them still, ~2mm (service manual says 0.8mm is the limit.) I didn't remove the shims so they are still the way around that I found them. That doesn't mean that the previous person didn't fit them the wrong way around (they look as if they would work both ways around, only way to find out is to swap them ) I'll stick some copper grease on it too, should have time for this today. Link to comment Share on other sites More sharing options...
Juvecu Posted December 19, 2009 Author Share Posted December 19, 2009 Just an update for the curious people who are wondering how this ended. I ordered new brake pads and seals. Took everything apart again, polished the pistons, put the seals in and then the pistons. The pistons were moving a lot easier after that (I could easily move them by hand.) The new pads were still getting stuck on the shims so I took the shims off and noticed corrosion built up behind them so cleaned the corrosion off with some sandpaper and put the shims back on. The pads could now move freely and had a bit of room spare for movement. I put it all together, fitted it back on the bike, bled the brakes and it's as good as new again. Lessons learned: - always replace the seals if they look a bit hard - check for corrosion behind the brake pad shims if the pads get stuck on the shims Thanks for the advice, hope this helps someone in the future Link to comment Share on other sites More sharing options...
2 Wheels Posted December 19, 2009 Share Posted December 19, 2009 Glad you got it sorted Link to comment Share on other sites More sharing options...
Recommended Posts