Supraguru is correct in all of his statements on how you optimize a brake system
Any of the engineers in here will understand why what he is saying is correct.
Slower rate of deceleration (rain) = more rear bias (less wight transfer equals more tractive force on the rear tires for braking
Higher rate of deceleration = more brake dive/more weight transfer/more front bias (regardless of suspension geometry, springs, anti's)
Amount of Brake Dive does not effect amount of weight transfer, deceleration determines weight transfer.
And as I said before the weight transfer in a steady state does not change no matter what you do to the vehicle suspension. If you decel at 1.5g's with stiff springs on the car or with soft springs on the car the weight transfer is the same, the only difference is the time it takes to reach the steady state and attitude of the car at this state.
Also without knowing anything on what Doward did to figure out his brake system (other than his quick post's on it here) it appears from his calculations that the bias of the brake system should be the same as stock (i didnt calc it out bc i dont care), assuming this is true the only real difference the BBK will get you is the bigger heat sink as others have pointed out on here. It is easy to lock the stock brakes up for a little while (until they fade) so the factory system is not lacking braking power, but instead lacks the ability to handle the heat caused by slowing the car down again and again. So assuming Dowards bias information is correct I am unsure why a BBK car would have much touchier front brakes.
Obviously Toyota made a non ABS Supra, do non-abs cars lock the fronts way before the rears? It appears that Zazzn is saying the fronts are locking way before the rears which I doubt is what occurs on a properly functioning non-abs car, and I agree with Zazzn that I would not want a car which locks the fronts way way before the rears. I would want the fronts to lock when the rears are entering/in their threshold braking zone. I do understand that the ABS will "fix" this but in my mind it is still a problem as the base line bias should be much closer to optimal.
Anyway, Zazzn, if you are still having problems just go back to stock until you have found a rear BBK to fit your needs. But again if the calcs are correct from Doward the front brakes should still lock at approximately the same time as the big brake kit. Again the only real advantage of big brakes is the ability to do mulitple stops in a row, not actual brake torque generated (stock brakes lock the tires easily once
). It looks like Doward used slight smaller total piston area on the BBK along with a larger disc to keep proportioning close to stock.
So just quickly running a couple VERY rough numbers Doward appears to be close to stock bias with his kit and therefore maybe something else is screwy on your car? Are you running the same pads F/R or something really aggressive up front compared to the rear? Maybe your stock proportioning valve is frozen in a position which really limits rear brake force...
Hope this helps
-Dave
