At the VIR races I experienced braking problems in both races. During the race the pedal would get REALLY long after a hard stop such as at the end of each straight. The next application of the brakes required pumping to get effective braking.
I currently have 2 two piston calipers on each front disk for a total of four calipers on the front end of the car. (See photo). At the back I have a single four piston caliper. All caliper pistons are 1.75 inch bore diameter. There is a 0.700 master cylinder pushing the fronts and a 0.750 pushing the rear. Even before I go out on the track with the amount of caliper piston area I’m pushing the pedal is long but firm and gives good modulation until the problem occurs. It seems to be heat related but I’m not totally sure.
After getting home and thinking about what happens on the track and considering some of the suggestions made by various people I’m plan to trouble shoot it as follows.
1. Replace the front rotors with solid disks. The ones on the car look like Swiss cheese. (By design I might add). I believe the number of drilled holes has compromised the mass of the rotor and they can’t reject the heat effectively. If you look closely at the rotors you can see stress cracks radiating from the drilled holes. I consider this to be a sure indication of to much heat. Anyone have a different opinion? See the photo below.
2. Take off two of the front calipers and run with just the remaining two on the front. The theory being the disk can’t dissipate the heat generated by four calipers fast enough. I’ve not seen any other car with the four caliper set-up except the Rakavon. They did however win the Runoffs!
3. Follow up on the suggestion made by Leon (Mitchell Racing Services) that the amount of caliper piston showing might be too much and I should be using shims to get the correct spacing. Correct meaning little, if any, piston showing out of the caliper bore. See photo – if you look hard you can see the amount of piston sticking out of the bore. This needs to be shimmed.
I’m open to other theories, opinions and suggestions. Ted S.