40mm Rear Caliper Viper Braking Performance
The stock Viper front brakes are Brembo 4-piston calipers with differential bore sizes of 38mm and 42mm. The Viper’s rear brakes are a 36mm single piston floating caliper design found on the 1988-1992 Renault Alliance/Eagle Premier and the lightweight Lotus Elise. Front to rear brake balance is determined by the ratio of the front and rear piston area. Because the stock rear caliper pistons are not large enough, they do not produce sufficient brake torque and the factory brake system tends to lock up the front wheels very easily.
By only changing to 40mm rear calipers, an otherwise totally stock 1994 RT/10 using street tires and factory brake pads improved from 0.8 G’s braking to over 1.0 G’s. Many Viper owners, racers, VCA officers, and Viper Techs have found the 40mm calipers provide greater rear braking power, better overall balance, and greater confidence. (40mm calipers do not add Viper Days Matrix points.)
The installation of 40mm calipers does not require modification of the factory proportioning valve nor is there any need for an adjustable proportioning valve.