RE: Re^2 RE: Disc Brake kits

[Luis Marques <marques@rtis.ray.com>]

"Smith, Kirby A" <kirby.a.smith@lmco.com> wrote: 
> Yes, you are right, my choice of words was poor.  The swept area does
> not increase with this concept, and thus the heat dissipation does not
> improve. However, the friction that can be applied in a single stop is
> doubled, as the disk is unlikely to overheat in that case.
> 
> kirby

If you keep the rotor the same and just add a second caliper, you have just
reduced the brake pedal pressure required to stop the car by half at the expense
of double the pedal travel.  The brakes won't grab until your foot is on the
floor unless you change the master cylinder for one twice as big.  Then you have
to worry about the rear brakes which are now only braking half as hard as they
should be braking.  All of this for reduced brake pedal effort and feel -
nothing more.

The rotor will get as hot as it got before because it is still absorbing all the
kinetic energy released when you slow down.  The pads will run a little cooler,
but not much.  In fact, the rotor may even get hotter because it may not be able
to cool as fast when you put another caliper around it and because it is now
doing a lot of the work that the rear brakes used to do.

So the bottom line is that just using two calipers on a stock rotor is a bad
idea.  If you want reduced pedal effort, get pads with higher friction
coefficients, or change the master cylinder for one smaller.  If you want better
braking ability, you have to go to larger/more massive rotors.

Luis Marques
'87 4kcsq