Brakes G60's vs UFO's and other combos............

[Dan Cordon]

Great points Alan-

Here's a specific example of a 'just the opposite' case for point #2. My 
honda civic si (we don't need to get on a tangent about poor design of 
hondas....) has many brake upgrades available, and many independent 
sources are testing them. What they've generally found is that with 
larger front rotors and nice 4-piston calipers there was no statistical 
difference in the 60-0 time compared to the stock setup. (Though there 
was much less brake fade over multiple stops). Even with stock brakes, 
the front end is traction limited, not brake limited.

When the installed a larger rear brake setup they measured a nearly 20' 
reduction in 60-0! This was also independent of which front brakes were 
installed.

Apparently in hondas design they were worried about giving too much rear 
brake proportion. I guess they didn't want the rear to lock up first in 
any situation, so they biased the front heavily. On the stock system, 
the rear brakes are more or less along for the ride.

But I must agree with Alan though....and I firmly believe Audi likely 
did a better job balancing the system for performance than honda did 
with my EG civic. Isn't that why the V8's and 200 20v's got better rear 
brakes when they got UFO's up front?

Aside from monkey lads not knowing anything about them, there's nuthin' 
wrong with UFO's. Actually, I wish my car had them :o(

Alan Cordeiro wrote:

> 1) Heat energy and temperature rise:
> The heat energy from the converted kinetic energy (1/2.MVsquared) of the
> vehicle
> will end up in the brakes. Small seconds of delay will not appreciably
> affect the final
> temperature. What really will, is the THERMAL CAPACITY of the rotor + pads,
> since the materials are similar enough (not like carbon fiber) it boils down
> to the differences in the MASS of the two rotors.
> 
> A small rotor will run hotter, and be more likely to fade under repeated
> hard
> braking e.g. under track conditions. Older brake fluid (with extra moisture)
> will tend to get hotter, and may require a quick bleed to get them back to
> normal.
> 
> 2) Concerns with moving away from carefully tuned/calibrated factory
> systems:
>   (the real reason I wanted to speak up)
> All these discussions have not addressed the concern of BRAKE FORCE
> DISTRIBUTION, critical to shorter braking distances (tires, Mu, etc being
> equal).
> brake system designers spend tons of design and test time, with
> sophisticated
> rear brake force distribution modulators, to ensure better distribution of
> the
> brake forces under the unusual weight distribution that occurs when a car
> is in hard braking mode. (Weight transfers from the rear to the front
> wheels,
> and hence the force on the rear rotors needs to be reduced).
> 
> If the front wheel calipers and rotors are changed, the BRAKE FORCE
> distribution may not match the weight distribution (or the rear modulator's
> adjustments) and hence provide inferior braking results even in ONE STOP.
> 
> ABS sytems will begin to release calipers that begin to lock rotors, to try
> and
> compensate, but their effect is a two edged sword. A chattering ABS braking
> stop is not doing as good a job as it could do if it were controlling a well
> balanced
> front/rear brake system, which would give higher braking force before it
> slips
> 
> Putting a huge diameter piston caliper and larger diameter rotor will give
> better
> braking force up front for the same pedal force, but the rear braking force
> will be
> reduced (since the pedal force is reduced), and hence the overall brake
> distance
> is longer, since the ABS will have to take over earlier if the force is
> sufficient
> to cause it to activate.......(front wheels lock up... remember, same tires)
> Putting an undersized front caliper-rotor in front will do the opposite, but
> the overall
> result is the same, "poorer" braking.
> 
> The best braking will be obtained if all wheels are held to just under 100%
> of the
> point where the tires will begin to slip. the engineers at the factory in
> Ingolstadt
> spend many months trying to get it to be the best....understand exactly what
> you
> are changing, and try and do it in such a way that the front/rear braking
> force
> distribution remains close to what it was (unless you think you can do it
> better..YMMV)
> 
> Sorry for the LONG burst....I didn't expect it to take so long...or so many
> words
> 
> Alan
> (yes, you guessed it, original UFOs..)
>