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Re: general question: Brakes

To: "Dr L. Kevin McNelis" <kmcnelis@nmsu.edu>
Subject: Re: general question: Brakes
From: "Robert M. Lang" <lang@isis.mit.edu>
Date: Thu, 21 Sep 2006 11:05:56 -0400 (EDT)
Hi,

There's a lot of reasons that racers go for larger brakes. But the most
important for a racer is the margin between "bite" and "complete, utter
loackup". This is described by racers as the "feel".

Think of it this way. If the braking force is measured as a curve, the
feel is the "area under the curve". More area under the curve translates
to better feel.

Also note that racers as a rule do not use power assist for the brakes, so
they have to make up the clamping force of the brake system with different
mechanical forces (pedal travel, pedal ratio, MC bore size, fluid motion,
etc.)

But the big thing for brakes is HEAT. More rotor size means better heat
distribution. The work done is the same, but the larger rotors distribute
the heat over a lager area. And, of course, vented rotors are even better.

But they also do it "because they can". In many cases (class rules, for
example) they cannot. And the most important reason why? If you go to
bigger, stickier tires, the inadequacies of the stock brakes become
apparent. Big brakes gives you a way to get the balance back.

As I have said in the past, the biggest part of the equation is the tires.
But if you can't overcome the tires with the brakes, then you can change
the brake system to bring things into balance.

That said, the folks that have to worry the most about the brakes are the
folks with heavy cars. Like Pony cars. Those cars are designed with
marginal brakes to keep production costs down. There is a def. advantage
to upgrading the brakes on those cars.

TR6 owners don't have the same concerns _because our cars are relatively
light compared to the brake rotor and caliper sizing_. But once you change
one aspect of the system, everything goes out the window and you're likely
to have to change everything. I just went though this with my race car.
The cage interfered with the brake booster - c ya latah brake booster. New
pedal box. New MC's. New plumbing. I haven't driven the car (yet), but
it's likely that before the car rolls under power that the front / rear
brakes will get changed (allowed under certain rules). Hmmmm. A totally
new brake system. Go figure.

Regards,
rml
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