A hydraulic prop valve can only restrict pressure, hence the reason that it is used to limit the rear. As the weight transfers to the front under braking, the rears tend to lock up due to the reduced weight and the adhesion being reduced, and the fronts will actually take more pressure until the adhesion limit is reached and they lock up.
Some street cars have front/rear prop valves that restrict the amount of rear brake pressure as the suspension height changes during braking, modern cars are all computer controlled.
Glen
--Previous Message--
: Not too sure about this "safety
: breaker" thing - without some real
: data to work with, I not sure I
: wouldn't end up killing myself! (I'm
: with ya, Glen )
:
: Did some research and it seems the
: proportioning valves (at least the ones
: I saw) only vary the rear brakes from
: 100% to something less than that. They
: cannot shift the brake bias any further
: to the rear by reducing pressure to the
: fronts.
:
: Did that make sense?
:
: Ciao Y'awl - Jim M
:
: --Previous Message--
: Wow, I think I have a "new"
: in
: the box old school safety breaker
: somewhere in all my old Spitfire race
: parts. Selling all that stuff so if
: anybody is interested I will dig it
: up.......
:
: --Previous Message--
: Any hydraulic proportioning would want
: to
: work on limiting the pressure to the
: rears.
: There used to be a device on the market
: called "safety-braker" that
: actually did that, it was a damper that
: absorbed any 'pressure spike" to
: the rears to prevent early lockup.
: You have to be careful though because
: the pressure required at each end
: changes as weight is transferred.
: That translates to sometimes it's
: better to minimize the things that the
: driver can screw with...
: (grin!)
: Glen
:
: --Previous Message--
: Hi Doug,
:
: Yes. That is an option too. I've
: already installed one on a friends
: modified Mustang. One question we've
: never answered though is: would the
: valve also limit pressure to the front
: brakes or just bias the rears between
: reduced and full pressure.
:
: With the Triumph's front/rear brake
: system split it would be easy. We
: could even do it "a la Formula
: 1" and put the adjuster in the
: cockpit! All we'd need then would be
: paddle shifters - lol (and about a
: hundred buttons on the steering wheel).
:
: Too much fun.
:
: Ciao!
:
: --Previous Message--
: Out of curiosity, rather than install
: twin brake master cylinders to keep a
: working brake balance, could you not
: install an adjustable proportioning
: valve to keep the bulkhead
: "stock" with only one MC?
:
: Doug L.
: --Previous Message--
: If you can lock up your front brakes
: under hard braking, going to different
: calipers will not give you more braking
: power - your tires are the limiting
: factor at that point. Both my GT6 and
: my TR4 use the same stock Girling 16P
: or SP calipers and both can lock the
: front brakes, once rebuilt so the
: pistons all move freely, fitted with
: braided stainless lines, good pads,
: clean rotors, etc.. Now, if you are
: going to fit huge, super sticky tires,
: maybe then you need more braking force.
: Once you change one component, it
: leads to another, as you pointed out -
: if you change the calipers, you may
: need to change rear wheel cylinders, or
: go to a dual master set-up with a
: balance bar, enabling you to put in
: different size master cylinders for the
: front and rear circuits . . . My advice
: would be to get the stock system up to
: max performance first and see how it
: works - with the right pads, lines and
: fluid, it's good enough enough for my
: vintage race cars, even in a one hour
: enduro.
:
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