From: noel shelley (noel@shelley1722.freeserve.co.uk)
Date: Tue Mar 02 2004 - 15:18:51 PST
Gentlemen ,
On the subject of brakes ,{ experts need read no
further } there are two types of drum brake configuration , Single or Twin
leading shoe .
In the twin leading shoe configuration the leading edge of both shoes are
pressed against the drum by two separate wheel cylinders or actuators . Due
to the self servo action of the rotating drum the shoes are pulled on to
drum , increasing the braking force , BUT only in forward motion , in
reverse the braking system is far less effective due to the loss of self
servo action . The need for heavy pull off springs is to overcome the self
servo action that might otherwise hold the brakes on . This arrangement is
normally used on the front wheels
Using the single leading shoe configuration a single wheel cylinder with
two pistons or a double sided actuator operates both shoes. Only one shoe
will lead and benefit from self servo action , the other will tend to be
pushed off the drum . Though less effective than the twin leading shoe
arrangement it does have the benefit of not being Directional and is normal
for rear brakes .
On some vehicles the hand brake will be found to be very effective when
facing down hill but rather weak facing up hill , now you know why .
Hope this is of interest Noel
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