From: Fred Martin (mung@in-touch.net)
Date: Wed Mar 03 2004 - 08:24:58 PST
Boy ,isn't that Noel great!!! Just the person to answer this next
question...Why is it that one shoe is longer than the other? I can see
his definition of the two systems in his post...but was wondering if due
to the lack of "pulling in" (no self servo action)of the rear shoe while
going forward...maybe the rear shoe was made longer to compensate for
this. A curious mind would like to know. Fred Martin
noel shelley wrote:
> 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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