We have been running the new rotary hillclimb racing car for 4 months now and during this time the car has performed very well with only a few small teething problems.
It is competitive but the braking system has not been very consistent, and it is hard to drive the car to the max when I do not have confidence in the brakes. The front brakes keep locking with the bias all the way to the rear, so we have changed the size of the rear master cylinder to 5/8” from 3/4” to get more rear bias but the front wheels keep locking under hard braking.
Front Brakes locking up
After some ringing around I contacted Brian Gore at Performance Friction Brakes, he was very helpful and he helped me sort out the mechanical side of the brake balance bar, making sure that the push rods are timed and the brake pedal is not binding up on the balance bar.
Brian also suggested fitting his Performance Friction Brake pad compounds (01) to get the best out of the braking system. We also checked the pressures in the calipers to rule out any issues with the hydraulic system.
We fitted the new Performance Friction Brake pads and went out to the next Hillclimb at Mt Cotton 2-8-09 to bed the new pads and to see how the system would go, and all went very well the brakes felt very predictable but for some reason the brake pedal would go to the floor on the first application and then on the second application it would be perfect nice and firm. After some investigation I found that the rear up-right bearings were loose in the rear up-rights and this was allowing the rotor to move around and force the pads back into the calipers, and this is why the pedal was requiring two applications to work correctly.
The first application would move the pads up to the rotors and the second application would make the system work correctly this is referred to as brake pad knock-back.
When I made the rear up-rights I was trying to save weight and I only used 3 bolts to retain the rear bearings in the up-rights, but this allowed the bearings to move as it was not clamped into the housings correctly. To fix this issue I have machined new 6mm thick steel retaining plates and added 3 more bolts, so now the bearings are clamped into the up-rights with 6 bolts and a large retaining plate, so now this will hopefully fix the pad knock-back and therefore fix the brake pedal.
We will find out how this goes at the next Hillclimb at Mt Cotton on the 9-8-09 fingers crossed.