Having just replace the rear rotors I now have evidence that the rear brakes are doing almost nothing. 250 miles and still have tooling finish. Previously I have replaced the brake fluid, DOT 4 BMW stuff from my mechanic, new pads and I have taken apart the calipers and meticulously cleaned them. I also polished the pistons with 1000 grit wet paper, very lightly. When I replaced the rotors last weekend the pistons retracted very easily in the caliper and there is no evidence of leakage.
What next? I don't think at this stage new calipers will help although the seal in the calipers did seem very hard and the rubber boots are in poor shape. Is there a repair kit? Is there an adjustment for front/rear balance? I have a firm brake peddle with no loss of pressure or spongy feel when stopped.

Thanks in advance.

Todd
1988 300E
Arctic White 81k miles