Wilwood adjustable proportioning valve - a starting point of adjustment??

[Blue96GTS]

New IPSCO brake proportioning valve kit to go with my new brakes. I need to take the car out and adjust the rear bias. I'm wondering if you can offer any advice as a starting point for this trial/error method. I envision myself becoming very good at opening and closing my hood on the side of the road...

I understand the knob adjustment allows for 0-57% bias, but I'm wondering where is a "close" starting point - 1 turn, 1/2 turn, 3 turns...??? Obviously a lot of factors here - just looking to get close.

Thanks,
Mike

[QuikHD]

I'm in the same boat. I'm guessing trail and error are the only way

[Bob Woodhouse]

Gents: I can comment on this but it is important what year Viper this prop valve is applied to. First some background, then a procedure I use to dial a prop valve in if what I share with you still applies.

Lets assume you have a 94 through 99 model year and you are using the original brake calipers. If different calipers, this will not apply. Somewhere between 98 up to 2002 the factory re-sized the rear caliper piston and I am too lazy to look up. This improved the situation some . And of course when ABS came on the cars the need for a prop valve went away. Anything stock, after 2003 I would not see you needing a valve. The issue that I will assume you fellows are pursuing is the front wheels lockup much sooner than the rear. This was a known issue on the cars referenced above running the "stock size" tire.


I am assuming too, that you are installing your valve in the front brake line, not the rear and that you haven't modified the metering/proportioning valve (non adjustable) that is standard on these cars.

PROCEDURE: On a flat paved surface I accelerate the car to about 35 mph and apply the brakes to leave about 4 feet of skid mark. Not too aggressive but enough so that I will eventually get all four tires to leave a print on the paved surface. Note the amount of difference between the front and rear skid marks. If you are leaving little to no rear skid marks, the front line pressure can be reduced with your prop valve. ( full out should be zero, once you get close, maybe a three or so turns, change only one turn each stop test) The pavement print I am looking for is about 4 ft of front to three feet of rear i.e. about a foot of difference. Should the front be less that the rear I will be ass over tea kettle at the first turn that was overcooked. I adjust and repeat until satisfied.

Now, one last comment to confuse the hell out of you, and me too since this was trial and error over years of testing back in the day. The factory combination metering/proportioning valve carries a check valve with a spring on it. We used to take the valve apart, remove the spring, then reinstall the valve. This allows the rear brakes to receive full pressure earlier in the brake application. Not a complete cure for the over-biased original condition but about a 70% fix. Cheap too.

Final comment, I have no interest in being sued for any reason. So what you read here is simply information and I do not verify its accuracy, authenticity, and am not recommending it. If you try it you are doing it on your own. remember, not advice or a recommendation. Apologies for using "I" so much, not an egotist, just want lawyers to keep their distance.