Adjusting ride height

[Autoban]

I measured my car ('86 Cab) and the right side front and back is 1/2" higher than the left measured at the center of the wheels from the Ground to the fender lip. I read in the Bentley how and where to measure and calculate the ride height. The book also shows where the adjustment bolts are. My question is, do you adjust with the weight of the car on the wheels, or do you jack it up, make an adjustment and measure where you are after the car is back on the wheels (kind of trial and error method)? Can you even get to the adjustment bolts when the car is sitting on the wheels?

[Oh Haha]

You cannot access the adjustment bolts with the wheels on the ground unless you have a lift of sorts. There just isn't enough room to move and get the leverage needed to loosen/tighten the bolts/nuts.

I have no idea your level of ability but this is not for the novice. You can really mess up the handling of the car if you get it too far out.

You will need some special tools and may even end up having to re-set your torsion bars to get that .5 inch

You will need to adjust the front and rear the same to keep the corner weights close to what they are now.

I kindly suggest you read some of the threads on this subject before starting.

[don gilbert]

As Wayne said, if your not exp. at this, you can spend a long time on it. Without scales, it is a trail and error process. Tri pod method is prob. the best way for the garage.

[wholio94112]

...i recently replaced stock front and rear bushings with those from rebel racing - and i thought that would be the hard part...being an automotive illiterate, i read thread after thread, wayne's bible, and bentley - and about three weeks later, i finally got the height right...but the alignment was in the red all around, in every dimension...i lost where i started from in regards to the torsion bars...i got confused with the idea of "independent suspension, and tried to fine tune right side or left side rather than the front or the rear...hell my wife was ready to leave me...read up on the list angles of your spring plates, and make them mirror one another...have a good, solid hydraulic jack to give you control over the spring plate and trailing arm alignment - otherwise you'll eat up your eccentric bolts...believe me, i know!!!
...i did it, so you can too...just don't go in oblivious, be detail-oriented, take notes and pics - and call it a night before its too late...
...best of luck...

[Porboynz]

In my experience you can lower the front suspension while the car is on its wheels with an allen key by reaching in behind the front wheel. If for example you lowered the front right by 1/2 inch by unscrewing the adjuster you would quickly discover that the left rear measurement has changed as you transfer diagonal weight off it. I always take the weight off the adjuster screw when raising the front suspension again by jacking the wheel off the ground. Without getting into corner weighting discussions, you can also make minor ajustments to the rear suspension by marking the springplate then jacking the car up and making a small calculated adjustment. Always take the car for a short drive to resettle everything and measure again. 1/2 inch is not much in the scheme of things, is that with you sitting in the drivers seat? I do know what you mean though, once you are aware of an apparent small imperfection like this it plays on your mind, perfection is expected. Have a play, but be very careful to record everything you do so at worst you can return to where you were. If you have a set of scales you can use the fun factor increases when you have to juggle fender heights with corner weights. I think there is an excel spreadsheet somewhere in my PC that calculates the diagonal weights to assist with these adjustments. Now that my 911 is a road car only I settle with fender heights being within 1/4 inch of each other side to side and the front being 1/2 inch higher than the rear, looks good to me.

[Autoban]

Guys, thanks for all the replies. As far as my skills, I used to hot rod VWs including splitting engines. I have done suspension work and body work as well including painting. On my Porsche I have changed the shocks, adjusted valves, improved the shifting by replacing every bushing in the linkage, adjusted the clutch and other minor tune up work, but I haven't dropped the engine yet.
I know about the corner balancing and at this point I have only noticed the difference side to side. I bought the car in January and always thought it is not sitting right, now that I measured the car it will not let go of my mind .
Rather than using the measurement of the height of the fender lip, I will measure as it is described in the Bentley. This should take any tolerances of the body out of the equation. I will report back what I find, but it will not be until next weekend. The Bentley gives the +/- tolerance for the suspension setting. If my car is out of tolerance, then I will have to make the adjustments.
On another thought, I don't think every Porsche came out of the factory corner balanced. I think they assembled the cars to factory specification and by doing so the corner balancing comes out within specification.

[will hung]

In all honesty, your car is over 20 years old, if the bushings are original, they are toast. Look at your spring plates, if the torsion bar cap is setting in the upper radius of the opening in the spring plate, the spring plate bushings are done. Likewise, if the bushings look original, they are done. Having said that, you can get replacement rubber ones from Elephant racing that are reasonably priced (if you can resist the "while I'm in there" bug). Having bad bushings can cause goofy ride heights.

With your history with Bugs and what you've done to your 911 so far, you have more than enough talent to straighten your ride height. Adjusting the front is easy. Just take the front wheels off the ground, remove the wheels, adjust the control arm to where you want it with a jack, set the adjuster. Literally, if you want to lower the car a 1/2", just raise the control arm at the ball joint a 1/2" with your jack and adjust the adjuster. The rear is trickier.

If you haven't found this yet, it is very useful.
911 Spring Plate Angle Calculator

Weigh your car and get the magnetized angle finder from harbor freight. If you can't weight it, do what I did. I knew the ride height of my car and I knew the torsion bar size, so I back calculated my weight. I then used that weight to find the spring plate angle I needed. I set the spring plate to that new angle and my height was where I wanted it. Maybe it was beginner's luck, but it worked.

My suggestion to you would be to use the Bentley method to get a very accurate ride height measurement. If all you want to do is set the ride height, set the rear first since it's the trickiest. Make sure the left and right side are very close because you will get a cross effect if it isn't. Then adjust the front to match the rear. The key to all this is to have your torsion bars indexed very similar side to side so that the adjustment screws are very close.

The problem is, you'll then need an alignment. If you decide to rebuild your suspension later, you'll need to go through all this effort and expense again.

[Autoban]

Will, the ride height calculator is cool. I have the protractor to measure the setting of the spring plate. I used it to rig my airplane and believe me, there are a lot of setting you need to consider to get that thing to the correct specification and to fly straight.
I don't have the weight of my car, but it is all original except the radio. I remember the Bentley calls for a 32 degree setting of the spring plate on the original '86 Carrera. I will measure this also next weekend to determine where my car is compare to the factory setting. A good thought on this thread was also about the condition of all of the bushings. I have not thought of it yet. Maybe this is becoming a winter project to take all of it apart and to replace all the 26 year old bushings. The problem with old cars (same as with old airplanes), when you start something you can get into it very deep.

[will hung]

Yeah, I originally intended to replace my bushings. Then I completely tore the suspension apart and replaced every wear item and refinished all the metal parts and then rebuilt the brake system.

The thing about measuring the spring plate angle, it's measured slack. So it needs to be unbolted from the trailing arm and the lower rear spring plate bolt (and its spacer) needs to be removed. So to measure it, you'll most likely ruin the current alignment.