Quote:
Originally posted by coyled
One of the things that I just learned is the amount of weight transfer that takes place in a cobra. The weight transfer if a function of a short wheel base, cg heigth, and traction. With street tires, you should run more rear bias then you would with slicks. With slicks, more weight transfers so you need a lot more front brake bias. My hi-tech static weight balance is 51% rear, 49% front. Under threshhold brkeing with slicks, the front is in the 72 to 74% range, the rear is 26 to 28%. Godd luck, scott
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Bingo!
The formula from my spread sheet for vertical force on both front tire (directly related to maximum braking and balance) is:
weight * ( 1- ( distance from front axel center line to center of gravity / wheelbase ) + tire coeficient of friction * center of gravity height / wheelbase )) + aerodynamic down force * ( 1 - ( distance from front axle to center of pressure / wheel base ) + ( tire coeficient of friction x center of gravity height / wheelbase ))
From there you can take figure the rear:
total weight + aerodynamic downforce - front verticle force.
In the example I was looking at the front brake torque was 10665 fl-lbs and the rear was 4919 for a 1 G stop or a front to rear ratio of 68/32. Up that to a 1.5 G stop and you get 72/28 and a .5 G stop (ever driven in the rain on slicks? if so you know what I am talking about!) 59/41. Begining to see why no one system will be at its best under all circumstances? See why street cars use proportioning valves and not bias bars? Here is something interesting, what you don't see is that total amount of brake torque is basically the same for a 1.5 G stop as it is for a .5 G stop. Think on that one for a while!
Rick