Replacement calipers

[Lou Borntrager]

Bob,

I am looking to replace my front calipers on my ERA, which was built in ’88. I noticed your manual states to use calipers with a 2-3/8” piston from a mid-size GM. The ones on the car now are approximately 2-13/16”. Wouldn’t the larger pistons provide better braking? Would these have come off a wagon or larger GM car? If I want to go with the larger pistons, would you know part numbers or what car to cross reference them.

Thanks,

Lou

[boxhead]

Hello Lou,
If you use larger pistons then there is a larger area for the hydraulic fluid to fill in order to push the piston out,so therefore useing calipers with larger piston diameter will decrease the pressure at the front calipers.
After saying this if you have an adjustable in line brake bias control then you can simply dial it in to how you like it : ie decrease pressure to the rear brakes, this will effect pedal feel.
Good luck with it

[Bob Putnam]

Lou,

Yes, the GM station wagon size was about 2.75" OD. Ulitimately, there's no advantage to one size or the other if the master cylinder is sized for a given travel at the pedal. If you need more fluid at the caliper, you'll need a bigger master cylinder to feed it.

Our "stock" master cylinder size is matched to the 2.375" caliper for the best front-to-rear brake balance, but if you're satisfied with the pedal travel and the rear brakes are working "enough" you could stick with what you have now. Unfortunately, I don't have part numbers for the larger calipers, but they fit mid-size mid-70s GM wagons.

[Lou Borntrager]

Thanks for the info...