How do I keep my rear camber from changing?

[A/SP911]

I have had a problem with the right rear of my 1980 911SC (with a steel widebody) changing camber settings when autocrossing for quite some time now and nothing I try seems to fix it.

I'm sure that the 275/40/R17 Hoosier autocross tires on 11" rims on the rear do put quite a bit of stress on the suspension but why would the left side be OK? I've had the camber shift positive enough to have the tire hit the fender wall which is unaccepable. I've replaced all the bolts including the eccentric twice with OEM parts, I took the trailing arm apart and cleaned it up, and even over torqued the bolts trying to make it stop.

Here are a couple of dumb questions that I have never found out the answer too as there aren't a lot of 911's involved in competition around these parts.

1) Is there any chance that between the plates on the trailing arm there is supposed to be that caulking stuff like on the front strut mounts? (I told you these are dumb questions...)

2) My aftermarket swaybar is attached to the end of the eccentric. Having never seen where a factory rear bar mounts or where other swaybar manufacturers mount theirs, could this be the cause of my problem?
3) Is their any chance that I could add the Rear CamberMax kit that Pelican Parts sells to help the eccentric keep it's setting?

Any thoughts? The season's about to begin and I don't want to be stuck under the car adjusting it between runs again.

Thanks
S.Chapman
A/SP 911
C/S 914
E/S 944

[jluetjen]

Have you ever checked your bushings?

[A/SP911]

I replaced the spring plate bushings with Neatrix last year and the rear trailing arm inner bushings on the bannna with Delrin the year before...

Thanks
S.Chapman

[Eagledriver]

Is the camber eccentric bolt turning? If not I don't see how you could be getting a camber change unless you are exceeding the range of the camber eccentric. The Delrin inner bushings cause the suspension to bind especially with large negative camber settings. Maybe this is part of the problem. My sway bar hooks up to the toe excentric bolt hole. Maybe yours is supposed to be there as well.

-Andy

[Tyson Schmidt]

Yeah, I'm with Andy. The inner banana bushing needs to either be rubber, or a mono-ball, period.

The arm needs to be able to twist as it moves through it's range of motion. The plastic solid bushings don't allow this, and will eventually break apart.

It may be the core of your problem here, but it's hard to say.

[A/SP911]

Originally posted by Eagledriver
Is the camber eccentric bolt turning? If not I don't see how you could be getting a camber change unless you are exceeding the range of the camber eccentric.

Yes, the camber bolt turns which I could never figure out why as the two large locating bolts don't back off. I rough it in at -2 deg with my smart camber gauge (no sense getting it accurately aligned at a shop) and it gains varying camber amounts depending on the course. I remember at the Cdn Nationals in Sanair a few years ago gaining 1.5 degrees as part of the course involved using the oval banking which really put a load on it when transitioning from the level infield course. I had to set it back after each run and drive slower on the latter parts of the course.

You can almost see the wheel starting to move in this picture:

The Delrin inner bushings cause the suspension to bind especially with large negative camber settings. Maybe this is part of the problem. My sway bar hooks up to the toe excentric bolt hole. Maybe yours is supposed to be there as well.

I had the problem before I changed the rubber bushings out. Also I went back and checked my notes and they are the Poly Graphite bushings not Delrin. Do the Poly graphite bushings bind?

I haven't autocrossed this car in a few years as I'm concentrating on my CS 914 but I took it out to a club event on street tires (2nd place overall FTD out of 30 cars ) and while I didn't have a camber guage with me I can no longer get my fingers between the fender lip and tires... Aaargh!

Any more ideas?

Thanks
S.Chapman

[Tyson Schmidt]

Yes, the poly-graphite bushings bind as well. Switch to mono-balls at your next opportunity.

The rotating camber eccentric is odd to say the least. Are you using the Schnorr washer under the nut? Although I can't imagine why it would turn even without this lockwasher.

[A/SP911]

I'll do that. My front torsion bar bushings also need replaced so this would be a good time to take care of it all at once. Maybe the bushings I replaced originally were not rubber?

I swapped out the eccentric, washer, and bolt with new ones. If I remember right the washer had a bunch of little teeth cut into it. I can't understand why it turns either as wouldn't I be correct in assuming that the eccentric just positions things and the locating bolts holds everything in place?

BTW I just looked under the car and noticed that the toe adjustment has no way to connect to an end link. Any chance that these eccentrics are interchangable and a mechanic got them swapped?

Hmmm... I'm starting to think that I have two problems that are creating one big one

Thanks
S.Chapman

[Chuck Moreland]

Originally posted by A/SP911
and even over torqued the bolts trying to make it stop.

Perhaps you have stretched the bolts and now they won't maintain torque. They'll need to be replaced.

My advice is to torque to factory specs. More is not better.

Is your wrench properly calibrated?

There are 3 clamping bolts, make sure they are all properly torqued.

Make sure they all have correct lock nuts.

Lose the plastic bushing.

The cambermax won't solve the problem, it is designed to easily setup the camber but not designed to support the weight of the car.

[A/SP911]

Good advice! Where's the 3rd mounting bolt? Going by memory I can only think of the two on the end of the spring plate fastened by part# 27, 30, and 28



Thanks
S.Chapman

[Quicksilver]

The 3 bolts are clearly shown in the picture. They are #27, #31, and #32.

31 and 32 are the special eccentric bolts.

[dfink]

I would say take the sway bar off the ecentric bolt and mount the sway to the trailing arm.

[Chuck Moreland]

From what I see in the diagram, the clamping bolts are 2x #27 and #31.

#31 is the camber eccentric bolt which does double duty, both an adjuster and a clamp.

The toe eccentric #32 does not clamp, it only adjusts. And it is bolted to the spring plate only, not the trailing arm. Hence moving the sway bar off the toe eccentric will not help.

[cbeers]

Wouldn't #33 be the clamping bolt for the ride height side of the plate?

I thought #31 is the eccentric for ride height?

Just checking.

-Chris

[dfink]

Originally posted by Chuck Moreland
From what I see in the diagram, the clamping bolts are 2x #27 and #31.

#31 is the camber eccentric bolt which does double duty, both an adjuster and a clamp.

The toe eccentric #32 does not clamp, it only adjusts. And it is bolted to the spring plate only, not the trailing arm. Hence moving the sway bar off the toe eccentric will not help.

You are correct sway bar could be attached to the toe location. I thought however that he had the sway attached to the camber ecentric. Seems like attaching the sway that far up the spring plate would offer little effect. Attaching to the trailing arm would offer maxmimum leverage for the sway to do it's job.
If he still can't hold the settings perhaps get everything set and tight. Then remove the toe ecentric and replace with a bolt, 2 washers and a nut. That should clamp the two plates.

[dfink]

Never mind the nut and bolt idea there is no room on the back side for a washer.

[A/SP911]

Here's the full link with the parts list I got off of our Host.

-There are two #27's that hold the bannana arm to the spring plate (the second bolt is not shown but goes in the top hole)

-#31 is the Camber eccentric (and third locating bolt ...and what my swaybar is attached too)

-#32 is the Toe eccentric

Ride height is only fine tuned by adjusting the bolts on the spring plate that aren't shown on that diaghram. Hopefully this will help with the confusion.

Originally posted by dfink
I would say take the sway bar off the ecentric bolt and mount the sway to the trailing arm.

Anybody got any pictures of how they may have done this?

Thanks
S.Chapman

[A/SP911]

We'll I just ordered up some Elephant Racing monoballs and bolt hardware from Pelican Parts. Here's hoping it solves my problem!

Thanks for all your help guys!
S.Chapman
A/SP 911
C/S 914
E/S 944

BTW has anybody ever come up with a way to attached their rear swaybar directly to the trailing arm instead of the eccentrics?

[chrisp]

If I remember correctly I believe the race shop that does my alignments replaces the two large clamping bolts every alignment. In fact I think they may have even commented that if the clamping bolts are doing their job, the alignment bolts can be removed.

[A/SP911]

It's been a few months since posting this question about my de-cambering rear ...but I thought I should share with the board that the Elephant Racing monoballs did the trick.

It took me a while to source all the bolt hardware, get it installed, set the corner weights, and align it all up again ...but it all paid off with a really good showing at the Slalom at Slemon in PEI this past weekend besting a gaggle of S2000's, 350Z's, Vette's, M3's, etc...

Why do they even sell the plastic inner bushings? After I disconnected the trailing arm it was quite apparent that the inner banana arm would only move in one dimension causing a major bind in the travel.

Here's a picture of the same type of corner as at the Cdn Nationals but the rear tire is staying put.



Funny side effect since I installed the rear monoballs, front strut monoballs, and the torsion bar polybronze bushings though... my front tire doesn't lift as much as it used to (even with the exact same swaybar settings)

Thanks for all your help guys!
Stacy
A/SP 911