Topic: Brake Bias
I did a brake pressure sweep on our car. Necessary brake input 'felt' to relate to 250psi front and 215psi rear @ the calipers. I have 4 piston calipers with 1.75" non-staggered pistons on the front and 1.375" non-staggered pistons in the rear. Calculations resulted in 65/35 bias (65% front). From one website, I read that vehicles from factory come with 60/40 bias, where other websites said the stock combo valves on older cars resulted in a very front biased system (but they did not quantify).
Drivers complained that the car was very unstable under braking. Our springs do amplify longitudinal load transfer under braking, but I would still think that 65/35 would be a more-than-adequate setpoint for this application.
I'm thinking that there may be a residual valve in the rear portion of the master cylinder? It was made for rear drum and is now handling disc. However, I'm not sure that little pressure buildup would cause excessive instability?
Thoughts?
forgot to add.....66/34 @ 150psi front; 65/35 @ 250psi front; 63/37 @ 400psi front. Appears to be very linear which would say that rear lockup is possible with increased longitudinal load transfers during extreme braking...but the complaint is unstable during all braking.