Miata Mailing List: October 1998, Message #48

sponsored by

> -----Original Message-----
> From: BHotaling@aol.com [mailto:BHotaling@aol.com]
> Sent: Tuesday, September 29, 1998 11:33 AM
> To: tblough@snet.net; Miata@realbig.com
> Subject: Braking Exercise...SOS but Different :)
>
> Are you saying that a larger pad provides no more friction
> than a smaller pad,
> it just uses less pressure on multi cylinder setups?
>
It comes down to unit pressure at the surface pressing the
two materials together.  If the pressure applied to the pad
by the piston stays constant, a larger pad has less PSI
pressing the two materials against each other than a smaller
pad at the same pressure.  It has less pressure per unit
area but a larger area.  The area term cancels leaving the
total force as the item of concern.

> Well, what if I use the SAME vs less pressure?  Will I not
> get MORE friction
> which may translate into MORE energy transfer to the rest
of
> the stopping
> components short of a tire lockup?
>
Nope, same pressure, same force.  The only way to get more
friction at the same pressure is to change pads to pads with
a higher coefficient of friction.

> I would imagine folks who upgrade their brakes from OEM
are
> looking for
> increased stopping capability and not for similar stopping
at lesser
> pressures.
>
> Specific example:   Many claim better braking after
putting
> 1.8 calipers and
> pads on a 1.6 (heck even Mazda did it :)   !.8's are
> significantly larger
> surface pads, no?   Where is the increased efficiency
coming
> from?   Please
> note that I'm not talking exotic compound pads here, what
> they do is something
> else...... this is about size of pads alone.
>
The 1.8 caliper has a larger piston than the 1.6.  Therefore
it can generate more force for the same hydraulic pressure.
The downside is slightly increased pedal travel with the 1.8
calipers.  The 1.8 cars also have the advantage of larger
rotors which provide more mechanical advantage to stop the
wheel rotation.


Tom Blough &
"Molly" '99 Red LP
tblough@snet.net
Avon, CT

If we are to abolish the death penalty, I should like to see
the first step taken by my friends the murderers.
Alphonse Karr (1808–90), French journalist, novelist