whats the difference?

[Oolop]

Is there a difference between a "brake proportioning valve" and a "brake bias valve"?

If they're different, what exactly do the do, specifically? (Just trying to clarify things if the two are really different after all, I'm a little confused).....(or I might just be over thinking things lol).

[jlevie]

Those are two different terms that both describe the same thing.

[Oolop]

Ok, cool. I did find this however that helped me understand it better. Although it's still a little confusing but at least I'm understanding a little better now:

http://www.stoptech.com/technical-support/technical-white-papers/proportioning-valves

Here's my problem: I've lightened up the rear of my car a little too much and now whenever I need to slam on the brakes, my rear kinda slides around because the rear brakes lock up too fast. My ABS doesnt work and I'm planning on deleting it. I'm thinking of installing a proportioning valve at the same time.

Any suggestions?

[Oolop]

So with this valve, all your doing is adjusting the rear bias? So would you install this valve on the line for the rear brakes?

And when you adjust for more bias to the front or to the rear, really, you're just adjusting the rears?

[jlevie]

Ok, cool. I did find this however that helped me understand it better. Although it's still a little confusing but at least I'm understanding a little better now:

http://www.stoptech.com/technical-support/technical-white-papers/proportioning-valves

Here's my problem: I've lightened up the rear of my car a little too much and now whenever I need to slam on the brakes, my rear kinda slides around because the rear brakes lock up too fast. My ABS doesnt work and I'm planning on deleting it. I'm thinking of installing a proportioning valve at the same time.

Are the rear tires locking up, or is the rear of the car just bring to come around w/o locked tires? With the stock bias valve the pressure on the rear pads is quite a bit less than on the fronts. Even with weight taken out of the rear of the car the fronts almost always lock up before the rears.

However, if you have messed up the front to rear weight balance and the rear is light, it will want to come around under hard braking from lack of grip on the rear wheels. The solution to that, and to get the handling better, is to get the weight balance back in a favorable range. You do that by taking weight off the nose and/or adding it to the rear. The handling will be okay if the weight balance is no worse than 51% on the front and 49% on the rears.

Removing weight from the front of the car is one way to affect balance. That can be done by deleting the the power steering pump, A/C, using a lightweight hood, etc. Another way is to raise the nose of the car w/respect to the rear. You can only go so far with that before you have to add weight to the rear.

While balancing the car you also want to get the corner weights right. Corner weights are actually more important than front to rear balance. Fiddling with the springs (or spring pads) on the light corners is very effective at correcting corner weight errors. But you may also have to add weight to the right rear.

Fiddling with brake bias is the last resort and should only be done after getting the balance of the car right.