caliper o ring install
Thread Starter
Heel & Toe
Joined: Aug 2017
Posts: 22
Likes: 0
From: St.Paul mn.
I guess the question is, are there 2 kinds of caliper pistons.Are pistons the same for lip seals,as opposed to O ring seals?
Last edited by ThomaswRoberts; Mar 24, 2022 at 09:37 PM.
Safety Car
Joined: Mar 2009
Posts: 4,191
Likes: 951
From: Corpus Christi, TX
Depends on whose kit you get. Some use duplicates of the factory pistons. Some others claim to have equal diameter shoulders on either side of the seal groove, which the factory ones don't. Overall, you could more or less swap pistons between lip seal and o ring types. The kit i got, about 20 years ago, had stock dimension pistons. The trouble I had was the o rings fit too tight in the caliper bores. The springs weren't enough to push the pistons out. So from time to time the brake pedal would go almost to the floor on the first push, and pump right back up the next time. I put lip seals back in. Others haven't had that problem.
Le Mans Master
Joined: Jan 2002
Posts: 8,913
Likes: 283
If I recall, the lip seal piston has a square profile, and the O-ring pistons have a radius profile. I did all four corners using a name brand lip seal kit from my local parts house. The seals shrank and became hard in a few months and had leaks, and an occasional pedal to the floor event. I ordered an O-ring / piton kit and have not had a single issue in the 14 years since.
Le Mans Master
Joined: Aug 2005
Posts: 6,541
Likes: 1,975
From: Temple Terrace Florida
Just buy the kit with the new pistons and O-rings. Most pistons that have been in service for a period of time have nicks in anodized coating. Brake fluid collects on the nicks and scratches and creates sludge. I think it's false economy not to install new pistons. I use a Teflon paste on the O-rings when seating the pistons into the caliper bore. You could also use fresh brake fluid to coat the bore for easier installation. Once the piston is installed, wipe any excess fluid from the bore. Jerry
Le Mans Master
Joined: Nov 2015
Posts: 7,470
Likes: 2,647
From: Really Central IL Illinois
Either way you go, check the condition and inside diameter of the bore for each cylinder. I found the apparent "rebuilt" rear calipers on R66 were bored beyond GM tolerances and the lip seals sucked air when the car was driven and when setting over the winter. Brakes are more important than anything else, so take your time and do it right.
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Safety Car
Joined: Sep 2007
Posts: 4,458
Likes: 331
From: Indy Indiana
yup, o-ring seals with new pistons , especially in the rear, are much more forgiving when your rotor runout spec is at or past tolerance.
and they are more forgiving on keeping the seal when you don't drive your car much.
and they are more forgiving on keeping the seal when you don't drive your car much.