Quote:
Originally Posted by AZ_1LE
Yea, not true.
Compounds are meant to start working at certain temperatures (you can find this info on Carbotech's and GLoc's websites). If you think the front brakes operate at the same temperatures as the rears, you're..wrong.
If you put XP12's on the front and rear, the rear pads will probably last 6x longer than the fronts, and it's because of how much harder the fronts are working.
I posted earlier about how I run XP10's up front and XP8's in the back for tracks that are less harsh on brakes, and it has worked out perfectly on this car. Running 10's in the back I'd probably be lucky to see the same amount of pad transfer as what I was seeing on the fronts. It is NOT advised to run the same pad compound front and rear.
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Braking is a dynamic process. While braking, there is load transfer on to the front axle and off of the rear axle. This is due to the forces applied to the chassis by the torque of the braking wheels, and happens even in a car with no suspension. The harder the braking the greater the load transfer. As the load increases on the front axle, the friction between the front tires and the road increases. Consequently, the front brakes can do more and more of the work to slow the car. The inverse happens at the rear axle.
You need the maximum combination of front AND rear brake torque to get that load transfer to the front in the first place. A properly designed brake system will have taken this into account and appropriate caliper piston area, rotor diameter and pad coefficient of friction will have been selected to achieve this. Typically the same pad coefficient of friction is chosen for the front and rear as part of this design process. Consequently, installing a pad with a significantly lower coefficient of friction in the rear can result in rear brakes that are unable to generate adequate brake torque for sufficient load transfer to the front axle. Therefore, there is less friction between the front tires and the road, and the front brakes will more easily overpower the traction available from the front tires. This is of course safer than having the rear wheels lock first. But if you swing the balance too far to the front, the front wheels will lock up far too easily and braking distance is made significantly worse.
So, saying that it's not advisable to run the same compound front and rear as a blanket statement is asking for trouble. Now, it just so happens that the XP10's and XP8's have a very similar coefficient of friction, and will likely not negatively influence brake balance if run together on the front and rear axles. As far as there being a benefit with respect to the temperature range, what evidence is there that the rears run cooler to the point of requiring a different temperature range? Sure they do less work, but the pads and rotors are significantly smaller and have less air flow. And, why does it mater if the rear pads last longer, so long as they generate adequate brake torque?
Nigel