Perplexing Alignment Issues
 

Thinking a quick stop at the alignment shop would be the last stop in my quest to solve a couple of issues with my '82 SC, I was flustered that it actually came back worse-off after a four wheel alignment the other day. I have two issues.

Problem #1.) When I got the car earlier this year it tracked more or less straight down the road but had a nasty pull to the right when the brakes were applied. But, strangely, not always! Thinking first things first, I replaced all four flexible brake hoses, flushed the system with fresh fluid, and installed a new set of brake pads up front. The wheels turned freely so I didn't think, at the time, it could be a stuck caliper piston.

Then I had it aligned. And, like I said above, that only made things worse! The car now drifts to the right constantly, and still pulls to the right under braking, but still not always!

As I recall, the alignment shop attempted to get near to 0 degrees camber on the front (saying that was the spec) but the struts were all the way up against the sheet metal so getting zero was impossible. I've talked this over with the shop and he has agreed to take another look at it, saying something about putting the camber back in since that might be aggravating the situation. According to him, everything was within spec when he finished.

So I'm trying to educate myself on this issue before I go back next week. Is this issue typical of these cars, or is there something else that could be contributing to the problem that I'm overlooking? Is there an optimal alignment set up for the street which I should relay to the tech?

One other thing worth mentioning is I believe it's the RH side brake rotor that is worn thinner on one side than the other. I pointed this out awhile back, to a different mechanic, while the hoses were being replaced but he didn't seem to think it a problem. Clearly, this would indicate a sticking piston (at least at some point) but the wheel spins freely now so I'm stumped on this issue.


Problem #2.) This concerns the rear, but may be related to the above issue? The RH rear wheel appears to have significantly more camber than the LH side, even after alignment. As for ride height, measured at the fender lip, there is around 1/4" differential from one side to the other. That doesn't strike me as much? (by the way, front heights are identical) I then measured each side from the bottom of the torsion bar bushing plate to the floor (thinking fenders lip heights might not be the most accurate point) and these dimensions were nearly as identical as they could be.

So with all that said I'm wondering if I don't really have multiple issues? Can the rear wheel issue push the front end around that much? What did my alignment guy align if the rear camber issue remained after he was done? I watched him the whole time and he did adjust the RH rear wheel, I just don't know for what. He's experienced with 911s and came highly recommended. Or maybe it's time to dig into the front calipers?

Any thoughts or suggestions from those who may have been down this road before me would be greatly appreciated!

Cheers,
David

cWhere are you located?

It reads like you need a corner balancing.

Hmm, uneven rotor wear, that is definitely brake related. Get a IR thermometer at HB for cheap, Run the car until hot and then take readings. If extremely uneven heat, you found the culprit. You really should change the rotors after you find the fault, probably a sticky caliper and maybe a rebuild in order.

Did the shop give you a readout of the adjust specs? FYI, not all shops can align our cars, it is very very complicated and requires extreme patience and experience to understand the two eccentric adjustment bolts in the rear. I doubt they even toughed the rears.

If you change the front settings the rear is affected. If he didn't check/adjust all 4 corners then it wasn't done right. If you have more front camber on one side than the other it will pull to that side.
For a n.a. street car I like -1 -1.5 front and -1.5-2.0 rear camber, 1/16-1/8 toe out front and 0 toe rear.

It could be a sticking caliper like mentioned above. Is it pulling the first time you brake? Could be sticking when it gets hot which might explain why it seems random.

I would find a Porsche shop that can do 4 wheel alignment & corner balance. Also have them check the suspension components for wear.

The guy who does mine put weight on the front of the car to simulate the down force of driving then sets everything up to spec. I can take my hands off the wheel for periods of time and the car drives straight ahead. I can also pull the same stunt with heavy braking - good luck it should come right :)

This sounds like the piston in one caliper has more friction than the other. When you press the brake pedal one piston will react a little quicker than the other, and the car will pull to one side.

These cars will pull to one side unless the road is perfectly level. Most roads are slightly curved for rain water to run off, but if the road is perfectly level the car should go perfectly straight.

These cars were assembled by hand so measuring from the fender lip is not an exact method. Provided the car is placed on a level and flat floor, measuring between the floor and the center of the torsion bar covers is the way Porsche recommends it to be done. If those measures are OK, then the ride height is OK.

/Peter

Double check the brake issue first.

What is the difference when the car pulls vs when it doesn't? Is it on different road types? Roads with crowns vs level ones? How is your tire wear? Any fast wear, anything uneven? Inside, outside, shoulder wear, feathering?

I second the suggestion to consider a corner balance. Think of a four leg table. If one leg is longer than the rest you get some weird instability. The corner balance will even your cross percentages (opposite leg) so that the car is stable as possible.

Then, get a fresh alignment, and post your results.

Rebuild the brake calipers.
Post the alignment numbers. Front castor is what you want to look at first.
Make sure the tires are not worn.
Get it aligned and corner balanced by someone that knows what they are doing.

Almost all roads have crown, to facilitate drainage. No car will track straight on a road with significant crown. In the old days, technician used to set a little more castor in one side to comensate for this.

JR

Thanks for the replies and suggestions. I asked the alignment shop for a readout and he didn't have one. Maybe I should have known then. What I'm trying to decide is whether it's even worth going back. Not looking good so far!

I live in Northern Ventura Co., so CA.

Here's what I will do today.

1.) Take a drive today and check the caliper temps since I have a digital temp gauge.

2.) Recheck ride height using the center of the torsion bar covers as suggested.

Tire wear does not seem unusual. Car pulls the hardest under braking when the road is uneven or heavily crowned. Drifts off to the right now (after alignment) no matter what the road is like. Didn't do that before alignment.

cheers

I wouldn't bother checking the height numbers without your equivalent weight in the seat. The 150-200 lbs that you weigh is a major factor in the ride height corner balance set up. Find a shop that has done and will do a 911 corner balance and alignment and specify the type of driving you will be doing, otherwise you are going to be chasing ghosts. The brake temp check is valid though.

If you can get down to Van Nuys, TRE can set you up, great shop with knowledgeable staff.

+ eleventy billion...

I definitely wouldn't use the last shop that had the car. Plus, there's a neat automotive/aircraft/etc. bookstore in the Burbank area, where you can blow a half a day while your car gets fixed.

JR

Ventura County? Ah too far for us, I would check it for you.

Okay go to just tires and get a free read out or even sears, they will give you a read out.

If you ever in LA county, maybe you can swing by and I will check for you? SmileWavy

Keep us posted,

Jim

+1. Before throwing money at any of the replace this or that suggestions.....

Check corner balance with the Tripod lift method. Explained in these threads. Pick one or more: Pelican Parts Technical BBS - Search Results

Sherwood

Drove the car a little this morning but given it's 104 degrees now I'm done with diagnostics for the day! I heated up up the brakes pretty good and then checked the temps which were within 20 degrees of each other side to side so that's probably okay. I couldn't make it pull hard right under braking today, I'm starting to wonder if this is an intermittent sticking piston, as suggested.

I also rechecked the rear ride height at the center of the torsion bar covers and the difference is in the 1/8" range...easily explained by my less than perfectly even garage floor. Everything I'm seeing suggests the ride height is fairly even, it's the camber that's off.

I can get down to TRE if I need to. I don't have the time or inclination to chip away at this with someone who may or may not know what he's doing, so I'm leaning towards not taking it back to the alignment shop that just worked on it. I want it to be done right by people/someone who isn't guessing.

Here are a couple of pictures, I know it's tough to say much, but the difference in camber is noticeable to me.

Cheers

http://forums.pelicanparts.com/uploa...1410647880.jpg



http://forums.pelicanparts.com/uploa...1410647911.jpg

TRE can fix it. The other guy has already had his chance and that didn't get you anywhere.

JR