Adjustable brake proportioning valve

[logic]

Looking for a little expertise from folks who have done this before. Since my 2g will be down for an extended period while we build an engine, I'm planning on harvesting a few interesting parts from it for our 1g. Specifically, the front calipers.

This looks like a straightforward swap (along with new rotors and pads, and we'll probably do SS brake lines at the same time). What I'm curious about is the proportioning valve; the VFAQ suggests that the proportioning valve should be swapped with the target year's valve, which makes sense; with the weaker front brakes, there's a lot more front bias, which you don't necessarily want with the larger front calipers.

Has anyone gone with an adjustable brake proportioning valve? I'm thinking something along the lines of Wilwood's knob- or lever- adjustable valve:

http://www.wilwood.com/products/MasterCylinders/001-PV/
http://store.summitracing.com/eproduct.asp?N=120+400196+302053&x=20&y=11

I like the idea of being able to "dial in" the front/rear bias that works best for my driving style. Anyone done this? Any gotchas that you'd like to share?

 

[jtmcinder]

What year 1G and does it have ABS? Can't help without this info.

Also: your sig pic makes me wonder if the primary purpose of this car is to autocross ... if so, then do you left-foot brake?

- Jtoby

 

[ACM]

Also, remember that the car actually has 2 proportioning valves fitted, not one. The brake system is diagonally split, so to add an adjustable prop.valve to an otherwise stock system you'd actually need two - and getting two that perform identically would be quite the challenge.

The alternative would be to replumb the (rear) brake system. Since the AWD ABS functions in Select Low mode only, and always modulates the rears together, you should be able to run a single hydraulic line for the rears, thus allowing a single prop.valve to be employed. Join the two rear lines before the new prop.valve, then T back to the rear lines afterwards.

Theoretically, at least

Good luck with it !

Charles

 

[logic]

It's a 6-bolt 1992 Laser RS AWD, no ABS. I'm primarily autocrossing it right now, with an occasional pass down the dragstrip; no track use as of yet. Left foot braking: that's where I accidently mash the brake pedal when I clutch because my feet are freakishly large and I have the coordination of a drunken sailor, right? (More seriously: it's a skill I'm still trying to learn. Loose nut behind the wheel and so forth.)

Regarding the two valves: excellent point, I didn't realize there were two valves driving this (though actually looking at the car should have given me a clue), nor that it was a diagonal split. My original idea is now sounding rather half-baked, and I obviously need to do a little more research. Minor replumbing wouldn't be too much of a problem, but now I'm wondering what else I haven't taken into account.

In the interim, I'll probably just continue to run the stock prop. valve (the split point difference doesn't seem that far off between mine and the later OEM valve), while I think on this.

 

[jtmcinder]

Since you seem to be backing off on the idea, here's what I really suggest: Experiment with different pads, front and rear, to get more data. Keep learning to LFB, as it will be useful down the road (as it were) and changes the optimum front/rear bias for autoXing. In general, do lots of stuff that is cheap or free and simple to undo later.

- Jtoby