Alignment Frustration
 

I took my car to a highly recommended shop to have an alignment done on my '86 911. After his mechanic worked on the car for about 3 hours, he told me he could not adjust the "toe" on the right rear wheel. He indicated that the eccentric bolt did not affect any readings or adjustments at all. The equipment he uses is Hunter, which I understand is top-notch stuff. Any thoughts as to what may be going on here? Any recommendations for alignment shops in Maryland near Baltimore? The upside is that the shop did not charge for their time; the downside is that my time spent at the shop, waiting for the car, caused me to screw up a family movie night out for my wife's birthday...something tells me the lack of alignment carries a price after all.

As always, any help is appreciated.

Mike

did they put all 4 tires on sliders?

What is meant by "put all 4 tires on sliders"?

The car is parked on metal "pads" that allow the tire to be moved while the car is at ride height. Adjustments can then be made without having to jack the car up to get to the hardware.

I really don't know, wouldn't that be part of the alignment rig? There was much frustration at the shop. In any event, I am on the hunt for another shop in the Baltimore area.

Most likely the alignment rig would be so equipped. Seeing as how they have a Hunter, one could believe that they know how to use it.

I wouldn't worry about it too much.


Did they give you a readout of your specs before and after?

Post them here and we can see how "bad" it is.

I think the springplate and the right side trailing arm are too far apart. The gap needs to be cinched down, or the eccentric bolt head will turn and turn, and not act against the trailing arm. You are trying to pull the trailing arm either forward or back in relation to the spring plate, which has a circular hole for the eccentric threads.

The technique is to loosen the two rear springplate bolts, the swaybar mounting bolt, the shock mounting bolt, lower the trailing arm and spring plate, then adjust the toe and camber eccentrics. If the adjusting eccentric bolt stops working, then you have to tighten the eccentric bolt nuts up to squeeze the springplate and trailing arm together. It may take a couple of tries of tighten-loosen-adjust, then loosen-adjust-tighten before you get the trailing arm right where you want it.

Sorry if this is not making sense. You can do this adjustment at home with the right tools. It's a wonderful system really. It works, and it's light.

Our cars are old. Not many people know how to do it right anymore. Find a specialist that specifically knows torsion bar 911s.

The toe and camber bolts are cams. Understanding how the cam lobes affect the measurements is the first order of business. The cams can also be turned such that they contact each other and prevent additional adjustment. When that happens one cam can be rotated the opposite direction to nearly 360 degree to continue to increase/decrease the adjustment.

Unless the lobe on the toe cam bolt has been damaged or worn to the base circle (not likely) or the trailing arm slot damaged, the wrench should have been able to make adjustments.

The shock does not have to be disconnected. The trailing arm and springplate can be greased too to make it easier to adjust. This requires some disassembly then reassembly before making adjustments.

Thanks for all the very helpful responses. Am I correct in understanding that all of the adjustments are at the spring plates and not the trailing arms?

Thanks again.

Mike

http://forums.pelicanparts.com/uploa...1240172008.jpg

From this thread:http://forums.pelicanparts.com/porsche-911-technical-forum/469819-rear-wheel-toe-question.html

Soukus, have you found a way to measure the angle of the eccentric lobe to angle of toe/ camber? All I have ever been able to do is trial and error before I get the right amount of either.

Mike, the bolts have oblong holes to allow them to change the orientation of the trailing arm relative to the spring plate. The idea of greasing the spring plate sounds pretty good to me. I have to try that next time.

dad911, thats an intresting picture. The green dots intrigue me. Did you find a way to calculate the adjustment process for toe and camber? I understand the ride height adjustment. That one is pretty easy.

I have leads on 2 different alignment shops and will check them out first thing Monday. What damage might I do if I drive the car (other than wear on the tires)?

The adjustment (rotation of the cams to the toe or camber) is too crude for precise predetermination. What I do is dimple the bolt with a punch. See the dots on the end of the bolt in "dad's" picture? I put a dimple (with a metal punch) on the end to mark the top of the lobe of each bolt. This gives me a visible reference when I'm turning the bolt. I watch the bolt on the outside end and turn with a hand under and up around the trailing arm.

I suppose your could equate the cam rotation to the min and max toe (or camber) then devide the lobe swipe/rotation by the difference. That would get you started for a particular car, then you'll still have to fine tune it. I think the changes will vary slightly from chassis to chassis. I'm not sure the benefit of all this is adequate to go to the trouble.

I just take the bolts out, clean them and then dimple for the lobe reference, then set left and right lobe positions to match on both sides (toe cam lobes all to the front (3 and 9 o'clock toward front of car) and camber cam lobe at middle). Then I measure to determine where things are then adjust from there. Having a reference for the cam lobe really helps. By doing this, setting the toe and camber is the easiest part of a suspension rebuild...relative to right height setting in the rear....and corner balancing. Still..not difficult...wiggling around to make the adjustments for corner balancing in a tight garage is more time consuming :(

You shouldn't damage anything.

Thanks, I'm going to dimple them and use a dab of yellow paint next time. Shoot, I might even grease the eccentric lobe just to make it easier.

I do the same for the height adjuster bolt. Set the bolts on a work bench after you clean them up, and a small dimple is all you need. When you're making adjustments, you're only inches away from the bolts so even a small dimple will be visible. If you make them too big, then your precision may deminish.

My springloaded punch has a very small tip, so I might have to use it a few times to enlarge the hole enough to see it. What I like about this idea is that the dimple will outlast paint, which can be periodically refreshed.

On the ride height adjustment, I loosen the 4 bolts on the torsion bar cover, and move it outward. I move the spring plate outward enough to make it easier to get the ride height wrench in there. I also switched to longer torsion bar cover bolts for extra strength.

McMaster Carr has forged wrenches that fit perfectly between the chassis and the springplate. They are far better than the cheap cut wrenches you find for height adjustment. I have one in 36mm and 24mm. I've never had to loosen the springplate cover. On a rebuild I also put some grease between the springplate(s)...makes ride height adjustment smooth as butter.

Oh...I have bought stuff there. Thanks for the tip!!! McMaster-Carr