Mountain Bike Reviews Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
757 Posts
Discussion Starter · #1 ·
Anyone ever had this problem of the ceramic pistons shattering. I have been pretty impressed with my XT brakes- keep them bled and have replaced pads once before and was replacing the rear for the third time. No big deal I drop in the new pads and I notice that the right side piston isn't retracting making it impossible to insert the new pads and get the rotor between them. I think well maybe some air is in there and I should bleed them- can't even get the bleed block in place. SO I thought I will give the brake a quick pump and thats when I notice the left side isn't extending at all.

Ok so something more serious is happening I figure. Remove the hose remove caliper from bike and go to my work bench and notice the right side makes a grinding noise when I push on it (by this time I have removed the second bolt to open the caliper halves- nothing in there thats fragile and I have never opened these but I am careful)...anyways not only is the right side making a grinding noise but indeed the left side is frozen.

Frozen on one side grinding on the other I figure what the heck its not going to fix itself and I have gotten two years of service out of them- I pull the right side piston out and find the back half of the piston is shattered. I finally get the left side freed up and the same issue has occurred.

I have never had that happen, but I figure there's a logical reason for it and there is.

As best as I can remember once before when I bled the brake the bleed block wasn't inserted all the way and caused the piston to pinch the block at an angle...so instead of being parallel with the bleed block the extended at an awkward angle causing it to likely start fracturing. I think I saw on here someone did something similar.

Bummer- I will post pics later but if you've ever dropped a ceramic figurine or porcelain plate it looks about the same. Moral of the story be careful and go slow.
 

·
Registered
Joined
·
3,092 Posts
I'd go with your bleed block theory. Or when you pushed the pistons back to make room for the bleed block it cracked then, its how i cracked the phenolic piston in my old Hopes. I chipped the outer part of the piston, didn't leak so i just kept riding it to this day.
 

·
Registered
Joined
·
757 Posts
Discussion Starter · #4 ·
Pain in the butt - BUT just ordered a new caliper that comes with new metal pads so not terribly unhappy. $70 bucks seems like a decent deal free shipping. Should have it next week in time to start riding when I am back in town.

@Ratt - I was thinking of the same thing but the pistons are shattered more than half way up the side....I so wanted to ride today. Its been weeks since we had good weather.
 

·
~ B A D A S S ~
Joined
·
3,236 Posts
Thats the problem with shimanos, no spares, only complete "units".
 

·
Registered
Joined
·
2,318 Posts
Hmmm had I known that I might not have bought shimanos. That is a silly way to do business but, I dont really hear any stories about them breaking all the time.
 

·
Plays with tools
Joined
·
4,646 Posts
Thats the problem with shimanos, no spares, only complete "units".
Not like that's unique to Shimano though. It's certainly more cost effective to keep calipers, levers and houses in stock fro warranty and repair than it is to keep every single last part. As a consumer it's better to get the $15 part, but as a manufacture, distributor and bike shop it's way easier to do sub assemblies. Plus you can guarantee that the repair will be complete and not worry about somebody only replacing one part when a full overhaul needed to be done.
 

·
~ B A D A S S ~
Joined
·
3,236 Posts
Yes of course but sometimes you just need the little part(s).
 

·
Registered
Joined
·
535 Posts
I just did the exact same thing as the OP. Dammit!!! Bleed block slipped out, pistons pinched it at a weird angle. Had to use pliers to remove the bleed block, now the pistons are making a crunching noise. At least I'm not the only moron that's done this. Moral of the story, use the pin to hold the bleed block in place!
 

·
damned rocks...
Joined
·
2,602 Posts
I can bevieve this. One of my front pistons is making crunching noises. I was not beleading it or anything, the only thing I did was pushing them back with a tire lever with the pads on it to realign the brakes.
I'm thorn between buying a new piston, or replace the entire caliper with a SLX or a Zee.
 
1 - 10 of 10 Posts
Top