I have a few remaining adapters that allow you to adjust the rear brake bias proportioning 3 to 4 times higher over the stock, from the initial knee point for proportioning.
88 stock proportioning begins at about 200psi. Adapter allows adjustment upto aprox 870psi to the knee point.
84 to 87 stock proportioning begins at about 230psi. Adapter allows adjustment upto about 740psi to the knee point.
I also made a video to show installation but I didn't intend it for this audience which has a lot more technical know how. So bare with it. http://www.youtube.com/watch?v=HdkKM9o9b9k
After going over my notes from 2006 I noticed that some pre-88 Fieros did have the newer valving. So if you want one, instead of telling me what year your car is, check the size of the end cap with a socket or wrench. Tell me what size it is.
I got my new proportioning valve adjuster from Aaron installed, bled the rear brakes and the master, and quickly set the bias with some test stops around town, then headed out to Buttonwillow Raceway in Central California for two back-to-back days at the track.
Quick background: 1988 Fiero coupe with a 3.4 DOHC, Bilstein and Koni suspension, 700 lb springs up front, 475 in the rear, 12" C4 rotor upgrade from West Coast Fiero using stock '88 Fiero calipers and Porterfield R4 racing pads. 215/45/17 BFG Rivals up front and 275/45/17 BFG Rivals in the rear. The tires are staggered to match the weight distribution. The car weighs 2940 with me in it, with a 43%/57% weight distribution.
HOLY $#!&! Adding some more rear brake bias transformed the car. Three major things happened: 1) The front brakes no longer overheat after a few hot laps, because they aren't working as hard now that the rears do something. 2) Overall braking is SIGNIFICANTLY increased. I had trouble locking up the brakes. It just stopped harder and harder and harder. Braking was very progressive. 3) I can now brake hard enough without locking up that the brake pedal is finally down to the height of the gas pedal.... which means heel-toeing is finally possible. Fanastic!
Now I would say the two biggest, most important changes I've ever made to the car are matching the tires to the weight distribution, and adding this brake proportioning valve adapter. Great product.
Note that I can't make any recommendation for street use since I pretty much only drive this car to and from the track. The adjuster does allow you to go back to stock bias very easily though.
I think it was something like $130 shipped, but don't quote me on that. I think Aaron is pretty busy these days but if you send him a PM and be patient you should get a reply on price and availability. For a track car it's worth every penny.
