Re: [Amc-list] AMC brake combo valves (waste of time)

[Tom Jennings <tomj@xxxxxxx>]

On Sat, 24 Feb 2007, farna@xxxxxxx wrote:

> 
> METERING VALVES:
> Don't recall what text I read it from now, but a metering valve requires ~100 psi to open. That's what it takes to overcome the springs in the rear drum brakes. It takes maybe 1/4 of the total stroke to generate 100 psi on the brake system, which generates a total of 300-600 psi depending on component sizes and pedal ratio (adjusted to size of vehicle). If you've rebuilt drum brakes before, it's easy to believe it takes at least 100 psi to budge those springs!
>
> What they do is prevent the rear brakes from locking before the fronts, theoretically. At least all braking surfaces are starting to work at the same time. I'm not sure it really helps by itself. Once the fronts start working weight transfer becomes a factor. With nothing limiting the pressure to the rear brakes they will eventually lock as weight comes off.

But the metering causes the rears to operate sooner, not later,
than if there was no metering. It holds off the FRONT brake
pressure; the discs don't start to operate until there is
pressure in the rear wheel cylinders.


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