From: Mohler, Jeff <jeff.mohler@wilcom.com>
>Ive noticed that on our VR4, the front brakes get hot as hell (of course)
>but the rear brakes just never get very warm..at all.
>
>Will barely steam when applied with water after a run, sometimes I can
>almost grab the rotor.
>
>Ive been considering upgrading the rear pads to the Hawk ST+ that I have in
>front for extra grab.
>
>What issues would I run into doing this?
The issue I can think of is that it might be worthless or even
counterproductive.
The test of whether you should change rear brake pads should be the braking
performance of the car, not the relative temperatures of the brakes after a
run.
Normally, you could tell by the feel of the car during braking whether there
is any advantage in moving your brake balance rearward. At the limit, a
wheel will lock. So which wheel locks first? If your rear wheels lock, you
can use more brake power at the front, because your front tires will still
take more.
In your case, I suppose the car to have ABS. I have no idea how to tell
what's what in that case. Maybe some sort of data acquisition? Without
knowing what is really going on (which brakes the ABS is adjusting to
prevent lockup), I can't tell whether more braking power at the rear will be
an advantage.
But I do know this: Rear brakes become less important and front brakes
become more important as traction levels go up. The sticky tires you have
put on your car for autocrossing increase the traction level above the level
around which the designers created your braking system. To get higher
levels of deceleration, you need more braking power on the front brakes.
You have changed to aftermarket pads which I assume to have a higher
coefficient of friction to do this. Since the forward weight shift will be
greater at these greater levels of deceleration, it may be that more braking
in the rear is not required. The bigger and stickier your tires, (and the
stickier your surface, like good military concrete) the more your front
brakes have to work and the less the rear does in proportion to the whole.
Eventually, I suppose the rear can do less on an absolute basis. That is to
say, LESS rear brake power than stock may be required.
Brakes work by converting mechanical motion to heat. In these high-traction
situations, I would expect that the front brakes would create more heat.
That agrees with what you have observed. It does not indicate that you need
more rear brakes. It does not indicate that you need more front brakes. It
is just normal for hard braking with sticky tires on a good surface.
Phil Ethier Saint Paul Minnesota USA
Lotus Europa, VW Quantum Syncro, Chev Suburban
LOON, TCVWC, MAC
pethier@isd.net http://www.visi.com/mac/
|