Changing brake bias - prop. valve?

[Brando]

How is the braking system modulated? My car is non-abs... I'd like to increase the braking to the rear. Is there a proportioning valve that can be replaced or adjusted? What about replacing with an adjustable valve?

Thanks,

~B

[Techno Duck]

As far as i know, its not easily done on a n/a car.

I asked the same question on the Rennlist forums, and Travis from RennBay mentioned this...

"I think the best way to adjust the bias for a setup on the NA ( for total control ) would be to bridge the output lines from the MC with an adjustable valve in between them. This would bleed off some pressure from the fronts and put it to the rears under braking."

[Dave L]

I cant remember where, but I was reading about brake proportioning and I recall that bleeding off the fronts was a bad idea. I will seach for the article and post more details.

[Oldguy944]

Proportioning valves were originally to balance the
disc front/rear drum combinations, due to their different
mechanical(hydraulic) advantage in exerting stopping force.
I've seen newer valves on fuel dragsters and off-road cars,
but they have the same issues, type of brake and size, etc.

It seems the 944 has the balancing built in by the
size of the pistons and the pad size(rotor swept area) combinations. Even on ABS cars, the porportioning
is part of the complex valving from the modulator system.
Not sure you want to try this on the 944, before you try different compounds of pads on each axle. Just a thought
IMHO.

good luck here!

[944 boy]

In racing I have needed to use the trans as a brake because I needed way more braking on the rear. With lots of traction in the rear it definatly could use more power back there, maybe i could switch to a diffrent compound but it would be nice to adjust it for varying tracks and conditions. i.e. race/street/rain

[Brando]

The reason I ask is I have good pads all around and an extra inch compared to the front for meat in the back, still when braking the nose dives like an anchor in water... It is the same when "scrubbing speed" or "engine braking"... nose dives still. Either I've got too much pad grip in the front (not enough in the rear) or almost all of my braking is done by the front system.

In my 914 this is easy... Replace the rear p-valve with a "T" fitting... Then set your rear venting clearance. But on the 944... I'm assuming it's 2 separate systems off of the master cylinder. Which means my proportioning is done by the MC? Is that correct?

[SoCal Driver]

You are trying to drive the 944 like the 914. It's not the same.

[Brando]

I just can't resist... I feel like I'm mis-using the car if I don't push it to the full potential.

[SoCal Driver]

It's "full potential" is more than realized as it is. The car was designed to have the same size tires front and rear. Putting wider skins on the back does look good but is not how the car was designed to handle.

[gohan]

Add something like:

Wilwood Remote Mount Brake Bias Adjusters
Adjust front-to-rear brake bias while racing.

Wilwood's remote mount balance bar cable adjusters are used with dual master cylinder/single brake pedal assemblies to adjust the front-to-rear brake bias during the race--without leaving the seat! They feature a bright blue knob for adjustment, and a modifiable 5 ft. cable and housing for easy installation into tight areas. They include two labels for bias identification and fit all balance bars with 3/8 in. x 24 threads.

But I, most of time, have difficult time to get the right adjustment.