UKKid35

Can anyone post a photo, ideally showing location? TIA

smiffypr

Its mounted on the ABS hydraulic unit. See WM page 45-1, picture bottom left, item 8.

JWise

At least on LHD cars, it's on the driver's side near the front by the power steering fluid reservoir. Not sure on RHD cars. Here you go:

Speedtoys

And IIRC, that brown thing there, is changable for other rear bias values..of which I will probly go up one step with.

UKKid35

Thanks Jarrod for the photo and Smiffy for the swift reply.

jthwan22

So which valve should S4 convert to GTS front brake use?

JWise

Indeed it is. I should mention in case anyone notices the "33" stamped on mine, the stock 18 bar regulator has been replaced by this 33 bar version.

the flyin' scotsman

The bias valve for S4, GT and GTS are same..............18


I also changed to 33............much 'flatter' braking.

The 18 valve disconnected:

Gary Knox

There is also a 45 bar and a 55 bar brake bias valve. The 45 bar was used on the 964 cars, and some reports indicate it is no longer available. I have that valve on both my '94 GTS and my '89 S4 track car (obtained them from 964 owners who had changed to the 55 bar valve). Tried the 55 bar on the track car, and found it could frequently result in rear wheels overbraking in heavy braking whenever the rear of the car became unweighted (coming across a rise in the track). Went back to the 45, and I prefer it.

Gary Knox

RKD in OKC

I have the 55 bar on my GTS. I've had the rear lock up when the ABS turned itself off. I have externally adjustable Koni reds and have adjusted the rear rebound firmer to keep the weight on the rears longer to take advantage of the higher rear brake bias. Used the ABS off issue as an opportunity to adjust the rear rebound to keep the rears from locking up under threshold braking.

I like the rear being a little loose under heavy braking. It makes it easier to rotate the car into a 4 wheel drift on turn in. Optimal setup for me is the rear comes around when I turn in just as I start to lift on the brakes. Feathering in throttle checks the rear rotation and sets the 4 wheels drift towards the apex. Takes some practice to hit the braking zone to not overcook or over brake the turn in.

After an autocross event both my front and rear discs are a pretty blue that matches my car.

the flyin' scotsman

Gary/ RKD.............would you recommend either the 45 or 55 valves for the street?

How is the overal braking compared to stock?

RKD in OKC

For street I think the 33 would be just fine. You don't want to have the rear try to come around when braking up behind someone on a clover leaf ramp. Something you most definitely want to be prepared for when it happens.

Gary Knox

Malcom,

I agree with RKD when it comes to street S4's (unless the front calipers and rotors have been changed to the GTS size). With the significantly larger front brake rotors and calipers/pads, I wanted a bit more on the street GTS. I had a 33 in it for a while, but when I found a source for the second 45 bar, I bought it and made the change. I like it better on the GTS.

Gary

Marti

UKKid35

I can confirm that the 33lb valve I have fitted is 928 355 305 02

Possibly the single best change I have ever made to any car