Camber Adjustment: Early 911 Spring Plates

[tiwebber]

This is a really small project and most of you do this stuff in your sleep but hopefully this helps someone out there.

My right rear wheel rubs badly on the fender - i've posted about this. I measured camber and found that the left rear has about 1.6deg negative camber (negative camber means the top of the wheel leans towards the car a bit) while the right rear has no camber. People almost all suggested adding negative camber on the right rear wheel so that the wheel would lean more toward the car and then the tire might fit in the wheel well without rubbing.

Here's how I added negative camber to the right rear wheel:
First I jacked up the car and put floor jacks under the torsion bar covers. I then used the jack to support the trailing arm a bit so that there would not be too much tension then removed the wheel.


Once the wheel was removed I used a plumb bob hanging from a wheel bolt to the ground to mark a reference spot (both height and point) to see what affect the camber adjustments were having. I wanted to see the plumb bob raise off the ground and move towards the car a bit - this would indicate to me that the wheel was tilting towards the car from it current spot.

I then loosened off (just loosened a bit not removed) both bolts holding the spring plate to the trailing arm and loosened (again not removed) the bolt that affects camber. Once that was done I inserted a 12mm hex wrench (12mm is hard to find at a regular hardware store - I had to get it from an automotive supply store) into the slot at the back of the spring plate. The hex wrench had no space to move. My options were remove some interfering brake lines or remove the sway bar ball point end. I chose to remove the sway bar end (to do this I used leverage and a crow bar) but still had problems moving the hex wrench for adjustment. Lucky for me I had a 12mm hex socket that barely fit. I quickly found the hex socket needed to turn to the right (clockwise facing the spring plate) to raise the wheel up a bit (increase negative camber).
I kept turning until I had raised the plumb bob by about 3-4mm. I reassembled everything without too much trouble - I needed two crow bars (i dont have a C-clamp!) to get the sway bar end back on the ball point connection.

Last thing was to drive it to settle the suspension (it takes a while for the suspension to return to normal) and see if could notice any difference in handling. I did'nt notice anything which is fine by me because the handling seems OK to me. When I returned home I checked camber on the right to see if it looked about the same as the left which was my goal - but it was dark out so I will re-measure more closely tommorow. Only time and a bit of hard driving will tell if the tire rub is gone but at least the camber on both rear wheels appears to be the same.

[Chuck Moreland]

You're on the right track Tim. But that plumb bob method isn't going to yeild accurate results. You don't know if the sides are the same, you just know you moved it.

Take your measures with the wheel on the car, and resting on perfectly level ground (confirm with a water level). You can use a digital level held against the wheel. Alternatively you can drop a plumb line next to the wheel and measure the difference between the top and bottom of the rim.

[tiwebber]

Thanks Chuck. I was just using the plumb bob to help me see which way the wheel mount travelled when I adjusted the camber bolt. I did'nt know if I should turn the hex socked to the left or right to increase negative camber. So my theory was if the plumb bob raised off the ground or moved towards the car then I was adjusting the camber bolt the right way to add negative camber.

I used the plumb bob as you suggested to measure camber on the my wheels after I had "leveled" my garage using you water leveling method. The camber results for the rear of the car were -1.6deg for the left rear and 0deg. for the right rear. I did a quick comparison of camber after the the adjustments last night (using the plumb bob again) and the right side appears to match the left now...but I am going to check again. Both your methods worked great.

[dentist90]

Tire rubbing gone now?

[tiwebber]

I did'nt get a chance to have two big people in the car while I cornered hard to test if the rub was gone and now I have my suspension apart to replace the spring plate bushings and check the torsion bars. I am going to try and raise the car a bit from its current 24.5 (.5 of that came from the new bilstein sports) up to 25". I'll also try and get my camber back to where it was prior to installing these new bushings and reidexing the t-bars...it was about -1.6deg. I hope this does it. If not, my next stop is 15*7 wheels with more offset (if I want to put out more $'s) or smaller tires.

[jluetjen]

eh -- what size wheels and tires are you running now?

[tiwebber]

I have 7j*15 wheels (911.361.020.11 23mm offset) with 205/60/15 tires. There was about 24.5 inches from ground to fender lip with -1.6deg camber.

[74cookiecutter]

Tim, I run 205/60 15s Yoko's on my 74. and I don't have tire rub. I recently lowered it by 1". My ride ht is now 25.5 rear and 25.25 front empty. The rt side (passengerside) is about 1/8 lower on front and rear. Euro spec is 25 rear and 25.5 front I believe.

When I'm in the car it sits level at 25 1/8 front and rear and it's within an 1/8th all around. I weigh 165lbs.
My car has cookiecutter wheels though and this might effect the offset issue. I just finished resetting the ride ht week before last and then took it in for alignment. The rear camber is -1.4, Toe-in 0.
It feels great but I wish it was 3/4" lower in the rear for appearances not performance. I'm afraid of the tire rub.

I would tear back into the Spring plates but I just spent the money on the alignment...

For your situation I would drop the spring plate 2 degrees which should give you about 16 mm (5/8") of additional ht then check it after you drive it. If this puts you within 1/8 of 25" for the rear that would be great.

Keep us posted on what you find.

Robert