Jason F

Please help me, my car is barely drivable until I get this problem fixed.

I just had the "Big Red" 4 piston turbo brake setup installed on my 1977 911s (widebody with 17" wheels), and have a problem. The kit was purchased from The Racers Group, and all adapters etc seemed to fit very well per my mechanic ( a reputable local Porsche mechanic in the Seattle area).

Other than the lound squealing that is occuring until I properly heat up the brakes, I am having another problem which needs immediate attention.

There is some sort of a rubbing during moderate to tight radius turns at more than parking lot speeds when turning the car. It may be a tire on the inner or outer wheel well, but I think it is the brake disk rubbing on on the lower control arm. Rubbing never occured before the turbo brakes were installed, and the mechanic who installed the brakes ground down a portion of the lower control arm because rubbing WAS occuring between the brake disk and control arm during turning. He ground and then the noise was gone (until turns are made with a loaded suspension)

SO THE QUESTION IS...

1. Is it normal for the disk to rub on the lower control arm outer portion with the installation of 4 Piston turbo brakes.

2. If so, is grinding down the outer control arm an acceptable fix, or is there another standard fix to this problem.

Keep in mind that the car is "track" setup as far as ride height etc. It is very low, has TRG sways, and has moderately stiff torsion bar suspension.

The tolerance from the lower control arm to the brake disk is extremely close, and when turning the car under load, it seems that the brake disk is likely rubbing the control arm.

It is going back to the mechanic on Monday for another look and probably more grinding of the lower control arm.

Please help me figure this out! I trust my mechanic, but I also value the input and opinions of the many knowlegable people who use and monitor this forum.

Thanks in advance,

Jason French

1977 911S 3.2 Widebody
Keep Right Except to Pass... Pass it on!

Steve Weiner-Rennsport Systems

Hi Jason:

I've seen this problem a time or two, myself.

You did not say what wheels you have but the root of the issue is that the rotor hats aren't made correctly for installing these 322mm rotors on a 69-89 911. These big rotors WILL contact the A-arms before full steering lock and they must be clearanced to fit.

These hats should be offset a little more (and a corresponding modified caliper adapter) to move the rotor slightly outward so that the grinding of the A-arm is very minimal. In many cases, we've installed steering limiters to prevent this from occurring but its not the best solution.

The reason I inquired about your wheels is to help determine how far outward the rotor/caliper package can be offset. This is a variable, based on wheel offset and design. Wide-bodied cars do have more flexibility and sometimes using various Turbo hubs and spacers can aleviate this situation.

Jason F

Steve, thanks for the reply.

My wheels are Fikse FM-5 17 x ~8.5, and they were created for a 1976 turbo bodied non turbo car very similar to mine. There appears to be maybe 1 cm of clearance between the caliper and the wheel spokes.

Upon closer inspection, I see a rub mark on the fender well, indicating that the rubbing when cornering may be tire on fender.

It now seems that the installation of the brakes has caused disk rubbing on a-arm, and tire rub on fender.

Did the brakes change the spacing of my wheels in the wheel wells such that they are now rubbing when before they were not?

Who can determine what will be the right setup for my wheel/brake/hub etc... combo here in the Seattle area. It was PERFECT with my stock brakes, now I have problems.

Thanks

Jason French

Bill Gregory

Jason,

You may want to read over Bill Verburgs summary of brake options at <a href="http://home.nycap.rr.com/wmv/generalbrmd.htm" target="_blank">http://home.nycap.rr.com/wmv/generalbrmd.htm</a>

Steve Weiner-Rennsport Systems

Hi Jason:

LOL,...The first thing I must tell you is that nothing is perfect. When making any modifications or custom changes of any kind, one always makes compromises. Its simply a question of degree,.... When Porsche designed the 911 front suspension ,they never made any provisions for rotors of that diameter.

In this case, the design of the 69-89 911 front suspension does not easily accomodate this diameter of brake rotor with some other changes and alterations. Many variables such as wheel offsets, backspacing, rotor design, caliper mounts are all juggled to make these fit correctly. Even then, sometimes one makes compromises.

You can change some things to get better fitment of those brakes: wheel offset, brake rotor hats, hubs, etc but I would tell you that your fender rubbing is NOT directly caused by those bigger brakes; thats a result of tire width, diameter, wheel offset and ride height. Did you or the shop add or change wheel spacers?

Disc rubbing on the A-arms was most likely caused by those 322mm rotors and the hat offset placing them too close together.

I cannot tell you, here in this Forum, who to see about resolving these problems, but I can tell you that it IS fixable by someone experienced and knowledgeable enough to take the time to do this right. It also might take some different components than what you currently have to correct the situation and you should be prepared for that.

Bill Verburg

My info will be of no use. As Steve has said the rotor hat needs a bit more o/s. The caliper adapter will need a commensurate amount of o/s.

MikeF

Why not simply raise the front ride height by 1/4"? Not sure if it will solve the caliper rub problem but it should help alleviate any minor tire rub you're experiencing. 1/4" shouldn't be noticeable in terms of handling or appearance. One full clockwise turn of the height adjusters might just do the trick.

Just a thought...