Re: brakes

["Bill Thebert" <bthebert@domain.elided>]

I've been researching for an article in the next Binder Bulletin about brake
system design, tradeoffs, etc.  I've obtained a couple of engineering texts
on the subject, and consulted with some very experienced automotive design
engineers.  Here are a few tidbits I've uncovered so far:

DISC brakes are far LESS "efficient" in terms of how much braking torque
they produce per unit of energy that must be put INTO the braking effort.

A properly degigned DRUM brake system can easily produce much more actual
"stopping power" (even without a booster) for the same amount of pedal
effort.

In order to equal the stopping power of DRUMS, DISC brakes must apply much
greater pressures between the friction surfaces -- higher pressures which
are achieved by properly combining factors of surface area and fluid
displacement in both the master cylinder piston/bore and the caliper
piston/bore.

DISC brakes are far more efficient at dissipating heat than drums.  And they
are more "linear" in terms of how stopping power increases along with pedal
effort.  DRUM brakes (particularly the "self energizing" designs) will see
stopping power increase more rapidly as pedal pressure increases.

DISC brakes tend to be more "uniform" in their feel than drum brakes, and
are less prone to warping & consequent pedal pulsing.

Already I can see how BOTH of the statements below (about BIG trucks vs.
race/performance cars) can be true and soundly based.

I'm hoping that this article can settle once and for all the "front first"
vs. "rear first" LOCKUP debate that we've seen more than once. <g>

Regards,

Bill Thebert

>------------------------------
>
>Date: Mon, 22 Mar 1999 21:06:48 -0500 (EST)
>From: Ken Woods <kwoods@domain.elided>
>Subject: Re: brakes
>
>>     You say "disc brakes can be designed to give more breaking power"
>>the truth is that drums are much more powerfull. Have you ever seen a
>>big truck w/discs?
>
>Have you ever seen a CART|F1|SCCA race car with drums?
>
>- --
>Ken Woods
>kwoods@domain.elided
>