I’ve got some old Shimano SLX brakes from around 2002. I’m having problems with them in that the pistons aren’t reaching all the way out to the pads. I understand that after a bit of pumping they should sort or reset to near where the pads are, like a car does, but they aren’t doing it. I’m assuming the old seals are seized up or something. In order to fix this do I need to replace the inner o-rings or can I just replace the seals on the outside? I can find the seals for £5 but to replace the o-rings I need to buy the pistons and it’s more like £25.
5 Comments
fake_meows@sopuli.xyz · 2 pts · 333d
The square cross section seal is the one that flexes and pulls the piston back to a retracted position when you let go
The round cross section seal is a seal for fluid leaks
Having said that, a piston not coming out/ pumping out isn't clearly a seal issue. It sounds more like the brake needs bleeding / more brake fluid added. What have you tried doing to fix these?
twinnie@feddit.uk · 1 pts · 323d
That’s what I’ve been reading but I’ve bled them a bunch of times now. The brakes are stopping the bike pretty well when the pistons reach the rotor. I don’t see any leaks so I think I’m just going to replace the square seal.
fake_meows@sopuli.xyz · 1 pts · 322d
Stupid question:
Have you measured the rotor thickness?
From the description you're giving it sounds a little vague what's going on, but pads not properly reaching the rotor or stopping short can be a case of the rotor being worn past the limits. If it's too thin then the pistons run out of movement before things work properly.
On a shimano system I believe the nominal thickness is around 1.6mm. The minimum should be stamped on the rotor, it's usually 1.5mm.
Etnaphele@lemmy.world · 1 pts · 333d
Maybe I’m missing something, but isn’t brake bleeding/oil refill the first thing you should do? If no oil is leaking, maybe the seals are ok
twinnie@feddit.uk · 2 pts · 323d
Should have said but I’ve bled it three or four times. It’s not made any difference.