Brake proportioning valve

[Tomasz]

Hello,

As lately in this part of Europe we got constantly rainy weather I finally decided to do something with my brakes. Since I remember the worked unevenly distributing force firstly to left front wheel and then to right one. I could live with it on dry tarmac but not on wet surface. I've always suspected that the proportioning valve was to blame, as all the lines were changed some time ago. Yesterday I decided to get rid of the valve. Well it one of the decisions which you regret just after you make it

I have EBC Red Stuff kevlar pads in front and regular pads in the rear. Front ones have significantly higher friction coefficient although only when warmed up. I expected that the difference of friction (front vs rear) would compensate job done by the valve. And it probably would but the problem is that presently I can't warm up my fronts without locking rear wheels. Warming requires two-three hard brakings.
I don't want to come back to old proportioning valve as in fact it was something wrong with it. I would like to use adjustable valve which would allow for splitting braking power according to driving conditions. I found that such valves are very cheap (Summit Racing and Wilwood ones are for less than 40$) They allow for 57% of pressure reduction.
Does any of you has experience with those devices? Do they work well on 75/Milano?
I would appreciate any input.

[AR4me]

If you get uneven left-right front braking, like the car pulling first one direct and then starighten up during braking, then you may want to take a look at the front flex lines. They are prone to collapsing internally and causing this behavior. You do NOT want to remove the brake propotioning valve.
Jes

[Tomasz]

Jes,

Thanks for suggestion. My flex pipes are new and the valve is out of the car since yesterday. Uneven front braking disappeard, but now, as I wrote, rear wheels lock easily. I can't drive the car with such rear bias. It's simply dangerous.

[slyalfa]

The proportioning valve is only back vs front. never left vs right.(unless somone messed with the lines and mixed up what goes where.)

with the backs locking up so soon you might just not notice the real problem anymore.
but it it might be that somthing is moving is all the joints good? or one disk is different then the other or somthing sticking. is the pads wear the same?

[RSAE]

Tomek,

We have a Tilton lever-type proportioning valve installed in our race car. It has worked very well for us in many situations. We have ours mounted inside the car to be adjusted on the fly; I will post pictures when I get my main computer back in commission.

Here is a link to the part we have installed:
http://www.tiltonracing.com/content....ist2&id=37&m=b

-Damen

[andrewg]

At times when you start "improving" your brakes, sometimes adjustment maybe necessary to get back the proper front/rear bias. I have had a similar type problem with the ITS GTV6 years back. Running certain brake compounds allows the rear brakes to bite more that the front hence the lockup. I have wanted to install the adjustable bias valve like the RSAE students did, but never got around to it.

[Grant]

Andrew, are you still racing your GTV6?

[andrewg]

I changed careers in mid 03. I raced the GTV6 in 03 & 04. Spent 05 building business no racing . 06 - Had car repainted and working on making it pretty and other upgrades. Tried to get it ready for Nat Convention in Tulsa in June - I really wanted to run Hallet. My plans are to finish the work started in 06 and hopefully run a few races/track days before National Convention in August. Nothing makes you smile than beating the Z Cars, Porsche's, and BMW in a lowly GTV6 I will be updating my website when we run dates in 07.

[Tomasz]

Thanks for your all replies. It seems to me that the adjustable valve will make the job. Firstly it will compensate different friction coefficients of my front and rear pads and secondly it will allow for setting more rear bias which helps in tight corners.

From time to time I race against my friend in Porsche 944 3.0 (engine from 968). I would not lie if I say that his car by the default is more sport biased than 75/Milano. You can see it when it's braking aggressively attacking tight corner. Although he is not using his left foot it looks as if he's tailbraking. This is probably because Porsche applies more (than 75) braking power to the rear. Very helpful in some circumstances.

[RSAE]

I thought I had a better picture, but you can see the valve in this one. It is in the recession on the transmission tunnet between the seats (almost hidden by harness).



-Damen