ride height: fender lip vs. t-bar centers way out of wack

[Thrasher]

True, I replaced the shocks since the bushings, because when we pulled them loose, I noticed they were shot.

I ordered the Boges of the same part number, and even cross-referenced them on the Sachs website recently to be sure they were direct replacements. The very last number was different, but the Sachs website gives a range of that number all for the same application - like it's a revision number. The numbers are identical on both new shocks, but that last digit is the only difference from the old ones.

They are marked as "Gas" shocks, but I don't think they're high pressure.

It's entirely possible that the right rear (new) shock is not functioning properly, but it sure seems like it has better pressure than the ones I removed, and is similar to the other new one on the left rear.

I got the right side apart again last night and noticed that the spring plate angle was not at the 34 degrees I thought I'd set it at - more like 32.5 degrees.

I got the right t-bar reindexed at 35.5 degrees and will reassemble it tonight and report in. If the height is still off, I'll pull the rear shocks and swap them left-right to see if the odd behavior follows the shock.

Thanks for reading thru all of this. It's a little embarassing to be hung up on for so long, but maybe this will all help someone else in the future.

Craig

[jet911]

The problem may be your rear shocks. Very simple to rule out. Should have ordered Bilstiens...

[Thrasher]

Originally posted by jet911
The problem may be your rear shocks. Very simple to rule out. Should have ordered Bilstiens...

I just got the car in July, and the PO had just put on new Boges in front and I wanted to match those. I'll find out more tonight.

[Thrasher]

More lessons learned this weekend. Nothing is wrong with my springs or shocks, except that the rear torsion bars were not indexed correctly after the bushing replacement.

Yesterday, I went back to the tripod on the front end and noticed that my RR (which had been so low) now popped up to 25 3/4 and the LR (Which had been dead on) sunk to 24 1/2. That told me right there that the front had been so grossly off left-right that it was influencing the rears adversely.

When KurtV and I indexed the rears after the bushing refresh, we measured them with the front wheels on the ground. But, unknown to us, the front settings were so far off that our rear measurements were of no use. Kurt had used this method several times in the past with success, so why not on my car? Because he was lucky and I was unlucky. If you make the assumption that the fronts are close to balanced, then you'll be ok. But, in my case, the fronts were way off and we didn't get so lucky.

When I started playing with the tripod measuring, I was tweaking things more IN balance on each axle, but that threw my ride heights off. Classic case of ride height and corner balance not being in agreement. I had ride height ok when I left Kurt's place, but my corner balance was waaaaay off. When I started trying to balance it up, I threw ride height waaaaay off.

I still need to finish reindexing, but once I get my LR t-bar reindexed up (and at 35 degrees to match the RR), then I'll do a rear tripod and get the fronts equal L-R. If the rake is not correct F-R, then I'll just adjust the fronts up/down equally. Once I've got these dialed in, I'll try a corner balance and compare the results from the tripod to actual and let everyone know how close one can get using the tripod method.

I guess bottom line is, if you want to get you car balanced quickly, take it to a pro. If you don't mind taking a lot of time and want to learn about the 911 suspension, do it yourself.

[randywebb]

But, unknown to us, the front settings were so far off that our rear measurements were of no use.

- I'll repeat this, as it's useful information for us all.

[Thrasher]

Right. If KurtV is listening - do you recall what angle we set the spreing plates to ? I *think* we only set them back to the original angle and when we got the car together, the rears were really close to 25 so we called it close enough.

Now that I've set the RR to 35 degrees, as recommended by the spring plate angle calculator, I'm pretty sure it's correct, or at least very close.

Bottom line - I highly recommend:

1. using the spring plate angle calculator
2. checking your front heights and rear heights separately with the tripod method.

Once you have those balanced L-R, worry about F-R. I'd set the backs first, because you can easily predetermine the height using the spring plate angle. After that, then dial in the fronts.

[Rot 911]

Originally posted by Thrasher
Right. If KurtV is listening - do you recall what angle we set the spreing plates to ? I *think* we only set them back to the original angle and when we got the car together, the rears were really close to 25 so we called it close enough.

I am listening and I hope you are correct and this has been driving me crazy. Your car must really have been out of balance for this to be the cause! We did just set them back to the original angle.

[Thrasher]

Thanks Kurt - you don't remember the angle we set it to by chance?

I checked the "before" angle on the RR spring plate and it was only at 30 degrees. I've added 5 degrees and it's sitting at 25 3/4" now. That's with the front crossmember supported at its centerpoint and the front wheels removed.

I may have to drop it down a degree or so, but first I'm going to reindex the LR "up" to 35 degrees. That may shift some load to the RR and drop it closer to 25"

I'm not using the eccentrics until I'm sure I have the same spring plate angle on both sides. I'm just keeping them centered for now. I'll use the eccentrics to dial in the fine adjustments after that.

I'm getting pretty fast at reindexing the t-bars! Some air tools would be nice though.