Booster Install and Problems

[mahanian]

Originally Posted by Longhorn Man

GM says otherwise.
The drum/drum trucks have a distribution valve, not a proportioning valve.

I guess it depends on your definition of "distribution"? Some people swap the term distribution and proportioning. In my mind, a distribution valve would split the braking force 50/50. This would not be an ideal and I've never heard of a 50/50 split between front and rear. Even with a 50/50 weight distribution, as you brake the weight transfers to the front of the car, reducing the frictional force applied by the rear tires. You will lock up the rear tires and the front will not be optimal to stop the vehicle. Additionally, the distance the brake fluid has to travel plays a part on what bias to use. Although brake fluid is incompressible, the brake lines expand and contract, reducing the performance.

If the "distribution" valve has a linear bias I guess it work, meaning if it's a 60/40 bias the fronts would always get 70% of the braking force and the rear would always get 30%. But this would cause brake dive under light braking situations when weight distribution is close to 50/50. That isn't how a proportioning valve works. It is a 50/50 split and then it tries to follow the weight distribution curve as you increase the braking pressure....about as well as you can mechanically. Newer vehicles do this much better electronically.


This is just my 2 cents...