John Brandt

Greetings,

I'm having some problems with the car pulling left under hard braking that developed a while back i think but became noticable driving home from DE(left front consistently locks first) I'm sort of at a loss what to do next.
After 3 rounds of bleeding and not seeing bubbles, I assumed that calipers were the problem and I rebuilt the fronts. No change. The car has new Axis MM pads on all 4 corners, and I gave the rotors a good buff with a scotch brite pad. The brake lines are the only thing I'm curious about but that seem implausible because they are teflon/stainless braided and were new in the spring of '99 and now have about 15,000 miles on them including 7 track weekends. Do these develop weak spots that fast? Any Ideas on what else this might be?


Also I'm interested in hearing experiences with brake rebuild duration. Is 15000 miles including 7 DEs a typical situation?

Vampire

My car pulled hard to the left under heavy breaking when I bought it. (I saw a cop while "testing" it.) The problem was solved as soon as I put an equal amount of air pressure in each tire.

This may be too simple an answer for you, but...

Steve Weiner-Rennsport Systems

Hi:

May I add some suggestions here,..........?

First, I would say that one rarely, if ever, uses the brakes on the street as hard as you do on the track so many issues that might have been there for awhile surface during DE events.

Assuming for the moment that your flexible brake lines are OK and that you do not have any air in the system, brake pulling problems are usually caused by:

1) Alignment
2) Misadjusted wheel bearings
3) Poor corner weights (diagonally)
4) Sticking calipers
5) Tire problem with differering air pressures or separated carcass

See if one of these things doesn't fix this.

Good luck, Sir

--
Steve Weiner
Rennsport Systems

Jeff Curtis

I would definitely consider the corner balancing option, at least have it weighed to check...I had the exact same problem after upgrading to GIANT Wilwood calipers on the front of my SC.

After swapping struts, moving tires around, changing brake pads...the works...I weighed the car at a track event...there was a 260 lb weight difference from the drivers front and passenger front!!

This problem obviously entered this world when I performed a torsion bar upgrade in all four corners...months before upgrading the calipers to Wilwoods.

Once I bolted on the new calipers...boy did I have troubles. This problem put me in the grass a few times at VIR and Roebling Roads before I really started to realize the issue.

Again, it was a corner balancing issue, solved by bringing the right rear torsion bar up once notch...which effectively redistributed more weight to the passenger front...where the problem was.

R22tech

Just had my 85 in for service to correct this problem. My car would INTERMITTENTLY pull hard to the left whilst braking. I thought the same thing, maybe the brake lines were restricted due to inside deterioration and making the caliper drag or close faster than the rest. My mechanic checked it out and said brake lines fine. Calipers fine. Brake pads worn out, but EVENLY. Brake fluid in terrible condition. He replaced all pads and fluid with OEM parts. Says the problem is fixed. I get the car back today so I'll let you know if it worked. His explanation was that the "action" of the calipers due to the worn pads and rotten fluid was such that they would "****" sometimes and that would pull the affected wheel abruptly. I don't know, but the guy is a porsche racer and his shop is straight out of a magazine-you could "fine-dine" off of the floors and tools in this place! I felt very special about having him service my car. We'll see if you CAN judge a book by its' cover.

John Brandt

So would you say that the flex lines are likely NOT the problem?

Joe Abrahamson

John,

All things working as they should, the stainless steel brake lines should cause no more problems than the stock rubber brake lines in this situation.

If they are clear and not blocked in any way, then you need to look elsewhere for a problem. Jeff Curtis may have the solution as the Pcar is very critical to balance problems and you might want to look here.

JoeA

R22tech

Results in: No pulling at all since the new pads and excersized the calipers.

John Brandt

I did some more fiddling last eve and the calipers are indeed not releasing completely when hot. Given that I just rebuilt the calipers and I flush the system twice a year, i'm perplexed. The pulling happens/gets worse after several hard stops.

Bill Gregory

John,

Thinking about things that can go astray when rebuilding calipers: Were there any problems with the brake pistons themselves? Did you clean them up when you rebuilt the calipers? When you rebuilt the calipers, did you clean up where the pads slide? Corrosion can build up over time. Have you installed new pins (that hold the pads in) recently or are the ones you have rusted and crusty? Are the two caliper-to-strut bolts torqued to the right spec? When you rebuilt your front calipers, did you clean out the inside grooves, to ensure they were square? They can fill up with muck over time (when I rebuilt my 81's, they wasn't much crud in there, however).

Beyond that, have you looked at any of the non-caliper ideas mentioned in the other posts? On the list Steve Weiner posted, one item that could be affected by heat, after multiple hard brake stops, might be the wheel bearings...are they adjusted correctly? (With the tire on the ground, grab the top of the tire and push and pull it, pretty hard, in and out towards the strut and away from the strut. If you hear or feel any clanking, clicking, or looseness, you should check for proper adjustment).

On a way out thought....is your brake pedal returning fully?

[ 08-06-2001: Message edited by: Bill Gregory ]