[DML] Re: Low Drag Disc Brakes

["Elvis" <elvisnocita@xxxxxx>]

Bob - I may be too young and also I never really worked on
american cars, but what kind of difference could there be 
between regular pistons and so called low drag pistons ?

Compared to the force that is needed to reduce the speed 
of the car, the force that a regular (not rusty) piston
needs to move a bit is like nothing.

Also there is no spring that pulls the piston back, instead 
the big O-Ring pulls the piston back for approximately 0.1-0.3mm.

The piston does not really move in the O-ring, instead it 
pushes the O-Ring a bit outside with the piston, which then
pulls the piston back when releasing the pedal.
Moving the piston in the rubber O-Ring only happens to 
compensate the wear of the brake pads.

So from the theory how it works I don't see how the drag 
could be reduced a lot - and I see even less possibilities
to gain a lot from that.

But hey - a new day, a good reason to learn something new :-)
If you have more details, I'd like to know.

Elvis & 6548

>
> In the early 80s, cars shifted to low drag disc brakes.
> 
> For example, the 82-83 AMC Spirit disc brakes were low friction 
> compared to the 78-79 Pacer disc brake pistons. The parts are 
> interchangable so you can upgrade a Pacer to the low friction 
pistons.
> 
> What about the D?  Are these low friction disc brakes?
> 
> Are there later model calipers that are low friction.
> 
> Typically, the low friction pistons slightly retract after 
application. 
>   This could be a spring in the main piston that creates a  little 
> negative hydraulic pressure to retract the pistons.
> 
> Drum brakes used to do this with springs.
> 
> Bob
>




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