whate is this for- brakes?

[pete315]

there is a junction block at rear of car where all 4 brake lines go in. on other side of this block, there is a rod with a spring on it that gets attached to rear axle. besides making an annoying rattle noise, what is this for? do you need it? I removed it from my 92 SHO 2 years ago because of the same rattle noise.

 

[Shoaz]

That's the bias valve. It reduces the effectiveness of the rear brakes during hard braking in order to keep them from locking up, which can induce a spin.

 

[MOSHO92]

That is the rear brake biaser. It controls and limits the flow of brake fluid to the rear brakes durring agressive stopping manuevers. This way the rear tires dont lock up when you slam on the brakes (which transfers much of the cars wieght to the front wheels. It is there for a reason, but not everyone prefers to keep it. There is a plug kit that bypasses the biaser availible at some online vendors here. Then you can remove the spring and stop the noise.

If you install plugs just keep in mind that it is possible to loose control if the rear tires lock. Also, it is HIGHLY recommended to keep this biaser if you have upgraded rear brakes.

Hope this helped.

 

[pete315]

well then I guess I'll keep it on the car and look for another one for my 92. does anyone else rattle. I cant understand how it works. the rod is very loose. I wonder if it's broken.

 

[Shoaz]

Since you have a 92 you should have ABS. If your ABS is working properly the bias valve is less of an issue, but it's still better, IMHO, for it to be working properly.

 

[NWGRN94MTX]

Read the service manual on how to adjust it. Do you know the spec is + or - (IIRC) 3 mm? You need a caliper to adjust. Then I would check the bias with some controlled hard stops and a laser themometer. I would think if it's "rattling", it not adjusted properly anyway and thus not doing it's intended job.

 

[shopartsnw]

Rhe rod will rattle when the car is jacked up and the suspension is totally unloaded. WHen the car is at normal ride height with wheels on the ground, it should not rattle (much).

The adjustment spec is in the Helms manual, but the tolerance is +- .3mm, that is 1/3 millimeter. They can be a bit touchy to adjust, and even the factory setting might be wrong if you have lowered your car at all.

Adjustment is usually trial and error to get more or less rear bias. Move it in .3 to .5mm increments, and compare front and rear rotor temps under heavy braking.

- Mike