[urq] Rear 'proportion valve'

[fdekat]

THat 'proportion valve' that a lot have been discussing lately, in
conjunction with Ben's brake problems:

If you read the IST documents  that Martin has stashed on his web site
(www.quattro.ca), there is a good explation as to how that valve works.

It does nothing, until the rear brake circuit reaches a set pressure, then
limits the rear circuit to that pressure.  (Also has a mechanisim to give
rear brakes full line pressure, if front braking pressure is lost)

At 'less than heavy stops', I'm thinking that it has no effect, so perhaps
keep that in mind when doing your problem dignostics. (See chart inthe IST|
docs). Thoughts?

As those 'rear line limit valves' are notorious for leaking, the Tilton setup
sounds like a good alternative.

I'm curious as to exactly what that valve does or how it works?  Does it just
(adjustably) limit the rear line pressure (as the stock piece), or does it
variably modify the rear line pressure as a percentage of the front line
pressure? 


Regards,

=Frank de Kat=