911SC with Carrera Brakes and No Proportioning Valve

cay-ahe · 07-22-2008, 07:38 AM

I have an 1982 911SC race car that I have discovered has Carrera brakes f/r but no proportioning valve as shown in this picture.

I have had some undesirable results with too much rear brake and too much heat back there. When I look at the line shown in this picture it goes down to a "T" fitting for the front brakes. I does not make sense to me that I would put a limiting valve on the front brake line. Can someone help me with this?

Bill Verburg · Bill Verburg's Garage

If you have Carrera brakes f/r then you need the Carrera 33bar p/v or an adjustable p/v on the rear brake circuit

Your arrow is pointing to where it should be. But from the pic that appears to be just a through fitting

cay-ahe · 07-22-2008, 08:37 AM

Yes I have referenced your posts and web site trying to remedy my situation. Here is a picture of my car I don't know if this is a stock setup but I believe it is?? I don't know which line to work with here?

cay-ahe · 07-22-2008, 08:39 AM

Take two

Bill Verburg · Bill Verburg's Garage

Follow the hard lines off the m/c, stock, the forward one goes to the front brakes and the aft one goes to the rear brakes, each of those goes to a T which splits to L/R

cay-ahe · 07-22-2008, 09:14 AM

Bill, thank you for your help. Here is a better picture of the line coming off the MC. I'll do some more searching to find a spot to locate the proportioning valve.

euro911sc · euro911sc's Garage

hrmnn... I have the same setup on my ROW and have not experienced any braking dislikes. If anything, my fronts got too hot once at Limerock... Can you describe more what you are feeling? I have considered the addition of the valve, but it never made the hit list as I had no issues.

Best regards,

Michael

cay-ahe · 07-22-2008, 10:03 AM

I've been eating through rear brakes faster than fronts. I've also had the rears lock up in wet conditions unexpectedly which was less than desirable

. This setup is ok for autocross type stuff but on a track it is just too much for me. I've learned to apply the brakes very gradually but I'd like to get the proper balance if I can. This is on a car running 235/245f and 275r.

Zeke · 07-22-2008, 10:12 AM

You could change your pads in the rear to a less aggressive pad, or move to a more aggressive pad in the front. Won't help much in the rain, though, so I guess you better install the PV.

RWebb · RWebb's Garage

also gives a differential effect as the brakes go from cold to warm to hot... not he best but many people do alter the R pads

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by euro911sc

hrmnn... I have the same setup on my ROW and have not experienced any braking dislikes. If anything, my fronts got too hot once at Limerock... Can you describe more what you are feeling? I have considered the addition of the valve, but it never made the hit list as I had no issues.

Best regards,

Michael

Are you sure that you have '84-89 Carrera rears?

Carrera brakes are massively rear biased

The smart thing to do w/ an SC is to use Carrera fronts only and leave the stock SC Ms on the back. Then there are no issues

KTL · 07-22-2008, 12:04 PM

Quote:

Originally Posted by cay-ahe

I have an 1982 911SC race car that I have discovered has Carrera brakes f/r but no proportioning valve as shown in this picture.

That's my car!

Bill is correct. That arrow is not pointing to a pressure limiting valve. It's pointing to a union. The pressure limiting valve looks like a fat pale yellow-brown socket with some foam rubber wrapped around it

175K911 · 07-22-2008, 01:28 PM

When I removed the rear pressure limiting valve on my previous 86 Carrera, it really messed up the balance of the car at the track. It was the REAR that could actually boil the fluid, and I had far too much rear braking under threshhold braking into a turn at the track. Ended up putting the limiting valve (really just a spring loaded ball and socket device) back in.

175K911 · 07-22-2008, 01:29 PM

When I removed the rear pressure limiting valve on my previous 86 Carrera, it really messed up the balance of the car at the track. It was the REAR that could actually boil the fluid, and I had far too much rear braking under threshhold braking into a turn at the track. Ended up putting the limiting valve (really just a spring loaded ball and socket device) back in.

cay-ahe · 07-22-2008, 01:51 PM

Quote:

Originally Posted by 175K911

When I removed the rear pressure limiting valve on my previous 86 Carrera, it really messed up the balance of the car at the track. It was the REAR that could actually boil the fluid, and I had far too much rear braking under threshhold braking into a turn at the track. Ended up putting the limiting valve (really just a spring loaded ball and socket device) back in.

Exactly, I had brake fade problems at a race last weekend for the first time in a Porsche. It was in the 90's on a fairly tight course but not what I have come to expect from these cars. I have now gone to the Carrera rotors along with my quest to install a proportioning valve in hopes this all gets better. Now I'm going to have to come up with another excuse for being slow

.

Kevin, yup I stole your picture

.

911st · 07-22-2008, 02:02 PM

How and were would would one plumb in a Tilton adjustable bias valve?

cay-ahe · 07-22-2008, 02:17 PM

I was just talk with the guy who is going to do this for me. The plan is to cut a hole in the tunnel just aft of the front seats within reach of the driver and plumb it in there. I'm going to go with a rotary knob type adjuster vs. the handle 6 click position type. Infinite adjustment vs. defined adjustment levels.

911st · 07-22-2008, 02:34 PM

On a Carrera could one just plumb it in place of the limiting valve and put it on the dash?

No cutting.

911st · 07-22-2008, 02:36 PM

Maybe use flexible SS lines like at the wheels and make a kit out of it???

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by 911st

How and were would would one plumb in a Tilton adjustable bias valve?

The commonly available ones like a Tilton would be plumbed where the stock one is

There are remote adjusters for some that could be run to the dash. Haven't seen any advertised in a long time though

the usual cockpit adjustment is between the seats, this one is a hydraulic parking brake or line lock but an adjustable could be fitted here too.

JMO but the Tilton positive click stops are the way to go, they are repeatable and won't vibrate off where they were set.