Eccentric...how far will it move?
 

I have replaced everything in the suspension that was worn or aged. I have a 81 SC with adjustable spring plates. Can someone tell me how far I can expect the eccentric nut to raise or lower the car (range of travel)? I currently have it set in the center of travel but will have to mill a thin wrench before I can adjust tomorrow.

Mark

About 3/8" in each direction.

Kurt's nailed it. And that's assuming it's in the middle of its range when you start. You'll need to reset the torsion bars if you need more.

Ian

Oh and unless you just like grinding on wrenches, a bike shop with have the thin wrench you need for around $10.

I'm can't figure where I'm going wrong. I leveled the car in all directions on jackstands. I confirmed that I have standard 24.1mm
rear torsion bars. I then re-indexed the spring plates at exactly 34 deg. as recommended in the Bently manual for Euro spec hight.

When I've reassembled and taken it of the jacks my fender hight at the rear is about 25". It seems to high and 3/8" travel by the eccentric doesn't appear to be enough. Am I on the right track?

Kurt,
Thanks for the wrench tip. There are several good bike shops near-by.
Mark

Mark, the euro ride height is 25 1/2" in front and 25" in the rear so your rear height is just right.

What size are your wheels & tires? Height varies with different combinations.

Ian

Edit: Or should I say visually acceptable height . . .

I don't know from memory what size my tires are and I won't have access to the car until tomorrow morning. Maybe I'm "swallowing the camel and gagging on the nat". It just seems there is a lot of distance between the tire and fender lip.

As I recall they are the recommended size from the manual...

Make sure to move the car before remeasuring. Settles the suspension.

In my experience, I've found that moving the car isn't enough. I go for a quick drive in between trying to determine ride height. It's a pain in the you know what, but it settles the suspension better than simply moving the car and pushing down on the bumpers, IMHO anyway.

Edward

I agree. It takes longer, but when I perform suspension work on a 911 I always drive the car down the street and back between settings....and check the settings. So I'm anal :), but my work ain't no $19.99 Midas alignment ;-)

Something else...I only use the fender measurement as a secondary check. I use the torsion bar centers to set rake before corner balancing and alignment work.

The spring plate doesn't move much at the eccentric bolt, but keep in mind that the distance at the wheel is larger for the same angle of movement.

Doctor doctor, it hurts when I do that...

Figure out what your car weighs, then go here:

http://rennlight.com/cgi-bin/spring.cgi

Your car would have to weigh around 2600lbs in order to use a 34 degree angle with 24.1mm bars.

That 25"R Euro height is based on a 25" dia tire.

...and the angle quoted by Bentley ( nothing more than a repeat of the factory manual)....needs to go deeper if you have hi-pressure gas shocks ..or not. Especially difficult if you had one style and are changing to another....

...the angle used is then altered by 1 degree because hi-p gas shocks tend to raise the ride height....

Wil

I should have been more specific. Yes, driving it is what I mean by "moving the car". :) You know, rotate the tires!! :D

Souk what is your rake measurement at the T bars (how much and where do you measure it at)? I have been using the rocker and it isnt that accurate.

While we're at it, may I ask a question on angle of rake?

I've heard the "rule of thumb" that the front fender lip should be about .5" higher than the rear fender lip, and this should amount to an "appropriate" 1 degree of rake. We all know that fenderlip measurement vary, so what is the best way to determine proper rake?

FWIW, what I've done in the past is get rough measurements at the fenderlips, get it close to that .5" differential, then finalize heights according to fixed chassis points (eg. t-bar at rear or swaybar allen bolt up front) and the "tripod" method. What do you guys do to determine/set rake ...especially for a track car?

Edward

Sorry it took so long to get back. My tires are :front 205/55R16
and the rears:225/50R116. They are Falken Azenis. I got my wrench modified to fit the eccentric and experimented some with adjustments. I'm currently sitting at 25" at all four corners. Tomorrow as time allows I will measure the proper way .....torsion bar centers and wheel centers... to see how close to spec I am.

I have the front end pretty well aligned and when I reworked the rear I set the camber and toe in what I think was neutral position.

My question: will setting the camber and toe seriously effect the ride height?

Forgot to add that a quick measurement with a tape sets the tire diameter at 25".