Brake inbalance????

[panzerwagen]

I'm going too run Porsche brakes with 309mm discs up front & UrS6 OEM rear calipes in back with 288mm discs.
Are the 2 discs too close in size? Will I risk brake balance problems?? Can the OEM proportioning valve deal with the problem? Or will I need to go thru the BB task of plumbing in a auxilary valve?

[kwlw]

I'm going too run Porsche brakes with 309mm discs up front & UrS6 OEM rear calipes in back with 288mm discs.
Are the 2 discs too close in size? Will I risk brake balance problems?? Can the OEM proportioning valve deal with the problem? Or will I need to go thru the BB task of plumbing in a auxilary valve?

Discs size is not so important as caliper pistons are. Make sure that fronts are way bigger than rear. Don't know more about them.

But I know for certain - my car without propotioning valve (damn NPT-18/27 thread on Wilwood) is really dangerous, especially on dirty surface. Almost made my pants brown, when went sideways on braking near brick wall.

God bless 4wd! - stopped rotation with power contra steering...

So beware. Better do nothing than do wrong . If you will run into balance problems, proportioning valve may not help you, as it only "delays" rear braking.

Sau

[panzerwagen]

kwlw my Brembo 4 pistons should be ok up front....

and the rear is a single piston Urs6 rear caliper . Can it really affect my balance that bad?

[Sweeper]

kwlw: i **** my pants all the time when i try to brake more than half pedal. Front got locked up and rear doesn't work at all.

Does our cars have a so called "brake wizard" that control balance between front and back or no ? And to put if you have 332upfront and standart rear brakes ????

[90quattrocoupe]

I'm going too run Porsche brakes with 309mm discs up front & UrS6 OEM rear calipes in back with 288mm discs.
Are the 2 discs too close in size? Will I risk brake balance problems?? Can the OEM proportioning valve deal with the problem? Or will I need to go thru the BB task of plumbing in a auxilary valve?

You need a video camera and and proportioning valve. A Titon will fit on the end of you MC, where the proportioning valve is now. Vandervoort runs one on his S2 converted coupe. It is a lever type, I would prefer a dial type myself as it is more sensitive to adjustment. I run one on my 914, as I upgraded it to BMW 320i fronts. 40% more pad area than stock.

You set up the video camera so you it will take a video of the car as you brake in front of it. Turn off the abs, and run the car up to about 40 and brake so you can see how the wheels react to the braking. You proportion your brakes, until the rears lock up before the fronts. Then you back off the proportioning, until the fronts are locking up just before the rears. You can see all this on the video or feel it in your butt. The camera is just more effective at showing you this.

That is how you set up a proportioning valve.

So if you are concerned about it, put one one. It will fit between the end of the MC and the line coming out of it.

Greg W.

[panzerwagen]

So 90quattrocoupe what in essence you are saying is...

that NO, the OEM proportioning valve will not do the job ? If so then there is no reason to do this mod.
I was hoping to do this mod with as less drama as possible .
If I have to jump thru hoops to do this then I really don't need the headache.
The car is never tracked and is only used on weekends. The reason I was doing this mod was to get a better
braking system for the Winter and a better look to the rear wheels since I have Porsche Brembos up front and OEM in the back. The back brakes look lost back there. Call me hokum and a flamer but the car would look better with bigger brakes back there. I'm running 17's and the void is quite noticeable.
Thanks for the ops. Anybody wanna buy a vented rear brake kit ?
It has 4x108 bolt pattern though.

[90quattrocoupe]

kwlw: i **** my pants all the time when i try to brake more than half pedal. Front got locked up and rear doesn't work at all.

Does our cars have a so called "brake wizard" that control balance between front and back or no ? And to put if you have 332upfront and standart rear brakes ????

There are other threads on this forum showing my brake set up. But I will restate it here. 323X30 slotted rotor(one piece), 996 calipers, RS2 carrier in the front and 280X22 slotted rotor, UrS6 caliper, and S8 carrier in the rear. This set up is about the same size as the A8L runs in the states. I am running Carbotech Panther Plus pads all around. No proportioning valve.

Since I installed this setup two years ago, I have had 10 track days or about 30 hours of track time. I run just the Audi Driving Schools, so even though I run the advanced class, I always have an instructor, until signed off to run solo. Everyone of my instructors has made the same comment. They like my brakes. And these are guys running Alcons, Brembos, Stoptech, and other systems. In fact, at one event, the instructor, he runs Stoptechs on his S4, ask me when I planned on braking on the front straight. He could not believe how deep I went before getting on the binders.

At this last event, people would pass me on the straight, but I would reel them in on the braking going into the 1st corner. It didn't seem to matter what the car was running for brakes, or the kind of car. I was just braking better.

So in my humble opinion, if you upgrade the fronts, you need to upgrade the rear to get some balance back.

My 2 pence.

Greg W.

[90quattrocoupe]

that NO, the OEM proportioning valve will not do the job ?

No, not what I said. I said proportioning valve will do the job. As stated, Vandervoort and I both run one. His on a converted coupe, and mine on a 914. It just takes a little work to get it right. After the installation, it takes about an hour, to do the brake testing. Then you will have the braking threshold for both the front and rear.

At least the proportioning valve on the coupe is under the hood. Try it on a 914 where it is in the middle of the car underneath.

Put the damn setup on and then doing the testing. You can never expect to just bolt it on and have it work to perfection. Everything takes a little time and testing.

Greg W.

[panzerwagen]

Greg you misunderstand....

As I have said I'm running 309mm Billzcat1 specials up front with Porsche Brembos up front and inteneded to run
288mm vented OEM discs out back with UrS6 rear calipers. I didn't want too run Tilton or any other aftermarket proportioning valves on the car at all. My question was simply this....
Will I risk a brake in-balance running discs that close in diameter or am I ok? Will the OEM proportioning valve
do the job? If I have to run a Tilton or other valve then I don't need the drama. I will simply sell the kit.
If I was running the car on a track, then yes I would go to the Tilton or other after market. But I'm not.
It's just that.