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Old 04-07-2012, 05:42 PM
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Originally Posted by Irelands child
According to the Rock Auto Parts catalog, the Seville normally has 2-15/16" pistons for the fronts while the tried and true '80s GM Monte Carlo size car has a 2-1/2" piston. The Sevilles's are then 7/16" larger in diameter. I know you said that you have the e-brake calipers, which are supposed to be 2-1/2 - maybe - as it does look like there are some with the 2-15/16 rears just to confuse the issue

If you have the 2-15/15 version, this calculates as each front piston having 4.9 sq in of surface area with the rears at 6.77 or about 25% (round numbers) more surface area. A physics law(Boyle's) - "Pressure and Volume are indirectly propotional to each others. if you increase the Area the pressure will be decresed, and if you decrease the area of the applied pressure, the pressure will be automatically increased. Hence, pressure is indirectly propotional to area."

This tells me you might have a problem in that the rear caliper pistons may be too large and not giving you enough brake power. In actuality, those calipers should probably be in the 2 to 2-1/4 diameter range

Can you tell - I'm being cautious. Too dam' many variables when you deal with OEM 'stuff' adapted to our hobby cars (I really like my aftermarket Wilwoods )

Dave W
Thanks Dave.
The reason I'm going with the Cadillac calibers is the ebrake system which is easy to use and adapt to my stock truck ebrake system. I was thinking about going with the stock calibers like the front and be done with it and not utilize an ebrake at all. I'm sure that would fix my issue. The other option is going with wilwood or aftermarket caliber which are expensive but work nicely. I may also check into a line lock type system that locks the rear brakes when applied which I could use as a ebrake and would allow me to use standard front calipers. The Cadillac calibers weren't cheap either and it would be nice to have them working properly. What's the purpose of having 4 wheel disc if they don't work... Thanks for your help and advise!
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