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Saint caliper need replacing?

ChrisRobin

ChrisRobin

Turbo Monkey
Jan 30, 2002
3,350
192
Vancouver
What are the odds my rear Saint caliper needs to be replaced due to the seals letting air in?:

-I haven't bled it in a while but yesterday was the first time I went on a good ride and I can't lock this thing out. The last time I did bleed it, I did a pretty good job of it.
-It's the Saint caliper that doesn't use the finned brake pads FYI. Maybe it's just old.
-I've replaced pads, done the bedding in and all that stuff. I feel I still can't get it as strong as it should be.
 
Jm_

Jm_

sled dog's bollocks
Jan 14, 2002
18,978
9,638
AK
ChrisRobin said:
What are the odds my rear Saint caliper needs to be replaced due to the seals letting air in?:

-I haven't bled it in a while but yesterday was the first time I went on a good ride and I can't lock this thing out. The last time I did bleed it, I did a pretty good job of it.
-It's the Saint caliper that doesn't use the finned brake pads FYI. Maybe it's just old.
-I've replaced pads, done the bedding in and all that stuff. I feel I still can't get it as strong as it should be.
Click to expand...
Brakes are pretty simple. If the lever is spongy/inconsistent bite point, it means something is most likely up with your seals, but real old brake fluid can suck in air/water and have contaminants, so you try a bleed first. If you can get the lever nice and crisp again, then it's not the lever/caliper seals, it's contamination on the pads/rotor. If you can't, you've got a leak somewhere. Every time I've had a leak the lever performance has gotten inconsistent or deteriorated over the last few rides, again, brakes are pretty simple, either the system is sealed, or not, with new fluid, the lever will let you know. Any time you clean the pads (baking combined with cleaning in alcohol yields the most consistent results for me) you gotta clean the rotor with alcohol too, a trace of contamination is like poison oak, it'll get over everything again and will be the gift that keeps giving. I always spray down the caliper too (spray-bottle of alcohol) when I change pads or bleed.
 
ChrisRobin

ChrisRobin

Turbo Monkey
Jan 30, 2002
3,350
192
Vancouver
Well I did a quick parking lot bleed, slapped in some new Shimano metal pads and things seem ok. I was only asking because somehow if I look at the brakes wrong, they start f-ing up. Plus I've never run brakes this long before in the past. I figured there was some seepage somewhere.
 
P

peaslaker

Chimp
Aug 28, 2018
1
0
The way these things fail is that brake dust accumulates on the pistons. Pushing back the pistons puts that dirt under the seals and they get small leaks of oil. Oil comes out. Air hardly ever goes in. That oil (can be a tiny amount) contaminates the pads and that's the way that brake is going to be from now on - loss of power, noisy. You can get it back by doing a pad refresh and cleaning your rotors but the good pads will go bad really fast.

Just replaced a Saint M820 caliper for exactly this.
 
StiHacka

StiHacka

Compensating for something
Jan 4, 2013
21,560
12,505
In hell. Welcome!
peaslaker said:
The way these things fail is that brake dust accumulates on the pistons. Pushing back the pistons puts that dirt under the seals and they get small leaks of oil. Oil comes out. Air hardly ever goes in. That oil (can be a tiny amount) contaminates the pads and that's the way that brake is going to be from now on - loss of power, noisy. You can get it back by doing a pad refresh and cleaning your rotors but the good pads will go bad really fast.

Just replaced a Saint M820 caliper for exactly this.
Click to expand...
Easy - replace the pistons and the seals with fresh ones from Shimano.

Oh wait...
 
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