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[GMCnet] BRAKES [message #86966] Wed, 02 June 2010 12:31 Go to previous message
Charles Aulgur is currently offline  Charles Aulgur   United States
Messages: 78
Registered: March 2006
Karma:
Member
i'm confused. it is my understanding that going up to the wide shoes
does nothing to improve the rear brake effort so how can reducing the
shoe width lessen the brake effort?

--
Fred V
'77 Royale RB 455
P'cola, Fl

Fred, I'll admit it does sound a little confusion. I have no way of
telling what or how GM ended up installing 2" wide shoes in the OEM 2
3/4" wide drums. The area of brake shoes or disc pads that are in
contact does not even enter the equation for calculating braking
capability. It is based on the force that is being applied to the
brake lining or pad times the coefficient of friction of the brake
lining/pad material against the drum/disc material. Thus, changing
the brake shoe to a larger size, as myself and a lot of other GMCers
did after lessening to some expert telling us at rallies how it
provides more braking capability,
and applying the same forces (same size brake cylinder/caliper)on the
brake shoe/pad material reduces the force per square inch
accordingly and you end up with the same braking capability. It is
almost impossible to calculate the braking capability on drum brakes
because of their "self energizing" effect. However, it does make
your brake shoes/pad material last longer.
I would assume when GM realized they had to reduce the braking
capability to keep from sliding the mid axle and loosing vehicle
control, they probably reduced also reduced the wheel cylinder
diameter when they reduced the show width.

Chuck
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