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

[stlrj]

I use this angle finder placed on the door sill to rake the car. The ground must be perfectly flat, air psi correct, driver's weight, etc, etc. It costs $15-20. Spec is 1deg.

Ronin, where did you find that, in the Spec Book? Page? Official Porsche Spec?

I'm just trying to see if we can tell the difference between what is Spec or what becomes Spec over time as urban myth prevails unquestioned.

Cheers,

Joe Garcia
74 w/ 86 3.2
Redwood PCA since 1976

[RoninLB]

Originally posted by stlrj
Ronin, where did you find that, in the Spec Book? Page? Official Porsche Spec?

definately not in the P Worshop Manual.

I definately read about in in an old Pano article by Anderson or Allen Caldwell. I felt confortable using the door sill because I checked for any tub twisting before hand.

[randywebb]

The magnetic ones are the handiest ones, BTW.

There is also a new item made by Starrett I think that looks even nicer, thos it has the typical high price of all their tools.

[Gunter]

Thrasher: When you measure ride height, mark the position of the wheels/tires on the floor, then turn the car around and park the car in exactly the same spot and measure again. If there is a difference, your floor is not as level as you think.
I suggest that you install the bump steer kit (Make sure you loosen the U-joint in the smugglers box, with the steering wheel locked, before you push the rack up)
For the rear, I would go back to re-indexing the torsion bars with the eccentric bolts in the middle setting. (Disconnect sway bar and shocks, of course) When you are happy with the rear, leave it because the front adjustments are sooooo much easier.
There is no reason why 25" front, and 24.5 rear height should give any problems with the bump steer kit installed. These measurements result in a one degree nose-down attitude. Expect differences of at least 1/4" crosswise because not all tubs are equal. I have these heights with a Carrera spoiler in front, just be careful with curbs/driveways. I have a slight negative camber front and rear, a tiny toe-in, 7" & 8" wheels and I love it!
Aside from your height problems: Why are you running 245's on a 7 inch wheel? I can see 245's on 8" or 9" wheels.

[Thrasher]

Why are you running 245's on a 7 inch wheel? I can see 245's on 8" or 9" wheels.

They were already mounted on the Fuchs I recently bought, but seem to fit pretty well. I probably will return to the standard 225's whe I replace them, though.

Now another problem. Today I got back out there and started with the fronts using the "Ferch Tripod" method. Immediately, when I raised the back end, I noticed the driver side rear tire lifting much earlier than the passenger. When they'd both cleared the ground, the car was noticably leaning to the passenger side. The front ride height measurements were way different.

After some tweaking of front torsion bar indexing, I had them close and then dialed in the fronts to 25 1/2 with the adjusters. The front crossmember was nearly level and the adjusters pretty even. Great!

So, I dropped the car down and the fronts raise way up to 26 3/4 driver side and 27 1/4 passenger! I'm thinking the rear must be way off now. I raised the front end by the center of the crossmember (tripod) and measure the rears next - 24 3/4 passenger, 25 driver.

WTF? I'm off by 1/4" on one side in the rear and somehow that's jacking up my front end almost 2" ???

Something is not right here. I don't know what I can do now. I can't figure this out, because the front/rear ratio should take car of this.

Any suggestions are appreciated.

Craig

[RoninLB]

Originally posted by Thrasher

WTF? I'm off by 1/4" on one side in the rear and somehow that's jacking up my front end almost 2" ???

Something is not right here.
Any suggestions are appreciated.

Originally posted by RoninLB
I never used the method.
I can only guess that removing a small bit of spring tension from the rear by a rear center jack will enable you to level the front.. If raised to high then the front adjustment might not respond as easily.

[Thrasher]

RoninLB,

I see your point now that I re-read it, but in the archives Wil mentioned that it is not possible to shift weight fore/aft (or left/right) by raising/lowering one side of the car when it's raised as a tripod.

Seems counterintuitive to me, but I guess he's referring to the relatively low heights we're raising the car (< 45 degrees).

I'm going to try pulling the rear wheels and then lowering it down to 25" on the jack and re-measure the fronts to see if the higher jacking was indeed shifting weight forward and influencing the height.

Craig

[RoninLB]

Originally posted by Thrasher

I'm going to try pulling the rear wheels and then lowering it down to 25"

that sound like a great idea.
Sorry I don't have hard experience to offer.

[Wil Ferch]

I didn't enter into the discussion sooner because I had no concrete advice to offer..

At this point, I would kindly suggest that we review the basics to make sure we're not looking for exotic answers when the basics might have done it....

So....without any accusations -or such- of any kind, let me review:
- is the chassis "square"? Was it ever hit? Meassure left and right wheelbase...some of us get big surprises at this point ! Should be equal to at least a 1/10" or so.....
- when you adjusted the fronts.....you got them nearly equal and are the adjuster locations nearly equal, too? Are they both at ( say) midrange, or does one show the adjuster "tongue" high and the other low to get equal L-R front heights?
- you installed rear suspension bushings. What kind? If Neatrix, did you "bond" them to the spring plate or let them rotate? Factory rubber is bonded and spring plate angle, even if equal, may have more or less "rubber twist" preload when originally set to equal angle.
- when you adjust things and pronounce the goofy heights after lowering....is this the *immediate* setting , as recorded after coming down off the jacks....or did you first lower the car...and roll it forward and back a considrable distance? If you don't, you might get some goofy results.
- the tripod method is actually a factory procedure, and it seems to be important that the "pivot" point be as accurately positioned to true "centerline" as possible. Perform all necessary checks to make sure you're at "centerline".
- failing all of this....maybe we (all) are indeed getting a bit anal and are victims of torsion-bar-centerline factory measurement specs that may be wrong ( as I alluded to earlier). Maybe you need to simply do this --> get back to 25.5 front / 25 rear ( as it appears you once had)....even if the TB centerline spec is "off"....and with that setting go get a corner weight check done. Being "off" by 1/4" on either ends' L-R height measurement probably won't be a problem. Now check corner weights.....if LF/LR = RF/RR ( to a "close" degree)..then you'd be OK and this would confirm my suspicions that the factory specs on TB centerline measurements are indeed wrong....many can't seem to get this right....

Wil

[Thrasher]

This morning I raised the rear end, using the engine case (as central as I can get it) just enough to remove the rear wheels, then lowered it down to the 25" range. I say "range" because it was off a bit left-right. The driver rear was at 25 3/4" when the passenger side got to 25". The torsion bar centers were off a corresponding amount. Again, this is with the rear end jacked up to a tripod at roughly 25" fender height using the engine case.

Both Front fenders were set to 25 1/2". I also measured the ground to front torsion bar center and they were within 2mm of each other, but not near the factory spec for wheel center to torsion bar center. I thought the similar height, though to be a good sign, and maybe an indicator of a fairly true chassis.

I checked the rake and it was dead on 1 degree both door sills.

I remounted the rear wheels and lowered the car, watching the front end pop up to the 27 inch range, while the rears returned to nearly perfect 25".

Family duties took me away from the car, but I started thinking this could be shock absorber related. I did recently replace the rears with Boges, matching the Boges that the PO had put on the car just last year (and only about 3k miles).

I have the work order from Reid Vann (a pretty well respected shop in St. Louis) that states the correct part number for the front shock inserts. I also double-checked the boxes of my new rear shocks and the numbers are correct. I have not been able to verify the actual part numbers on the shock housings, though. But, I'd like to assume they're correct.

Could improper shocks cause this phenomenon?

Wil, thanks for re-entering. Here are the answers
1. I will do that, but what are good reference points that can be measured to that accuracy? Yes, I'm told that a deer ran into the right front wheel area about 2 years ago. I have the repair order from Reid Vann. They replaced the right front control arm, strut housing, ball joint and both tie rods, front strut inserts (shocks). They also aligned the car, notating some grinding was necessary to attain camber spec. However, the car drives pretty straight and again, Reid Vann is a very respected shop.

2. Yes, both "tongues" were relatively even in the range. That only happened after I reindexed the front torsion bars yesterday.

Yes, Neatrix bushings. But no, they were not glued in. The angle was checked with no load on the spring plates, before any twisting occurred. KurtV can you verify this?

3. After adjusting, I am bouncing the suspension by rolling it out into my driveway, then hitting the brakes abruptly going in reverse, then the same going forward. Sometimes I do take the car out for a short ride, but it doesn't seem to have any more effect than what I just described.

4. I think I had my jack pretty well centered in the rear, given the location of the engine case. I eyeballed it in the front on the crossmember, with the steering protective pan removed.

5. As for returning the car to euro fender heights, that would mean dropping the front end about 1.5 inches with the rear wheels on the ground. If I use the tripod method, I'm already there - but once the rear tires make contact with the floor, the front raises the 1.5 inches. I can't make it work both ways. I tried.

It's almost as though there is either not enough weight in the front end or too much weight in the rear end. My car is nearly 100% stock, and I've filled the gas tank to 3/4 and added my body weight to the driver seat.

I, too, think Occam's razor should be observed - it's got to be something simple.

[RoninLB]

Originally posted by Thrasher

Could improper shocks cause this phenomenon?

when I first set my height, the original/ 90k mi front T bar bushings needed a few miles to settle in.

[Wil Ferch]

Thanks for the additional detail, Thrasher.

You say this--->

"....This morning I raised the rear end, using the engine case (as central as I can get it) just enough to remove the rear wheels, then lowered it down to the 25" range. I say "range" because it was off a bit left-right. The driver rear was at 25 3/4" when the passenger side got to 25". The torsion bar centers were off a corresponding amount. Again, this is with the rear end jacked up to a tripod at roughly 25" fender height using the engine case...."

Maybe we need to focus on this...let me understand...the LR was 25 3/4" and the RR was 25".....I'm not quite sure where the TB centers are based on what you say. Is the LR TB center 3/4" higher off the ground than RR? Does this make sense? Has the "squareness" of the TB support tube been determined relative to the chassis?

I suspect there is still an issue from the deer hit. Simply take a metallic tape measure and measure from front hub centerline ( or more easily,,,,a tighter reference point like rear "edge" of wheel hub hole when the hub "cap" is removed).....to the same point on the rear wheel. Check both sides and compare.

On a lift.....do some sort of diagonal check...let's say the rear pivot of the LF suspension pivot to the RR banana arm pivot...and vice versa. I have a sneaking suspicion the chassis isn't "square" and a good shop can compensate to a degree.

I didn't read the whole thread, but didn't recall if front suspension bushings were refreshed. If they are plastic and weren't "honed" on the ID ( in an fixture to mimic "installed" external conmpresion), then there could be *binding* of the front suspension that doesn't freely come to rest at the same ride height.....Chuck Mooreland mentions this on occasion.....

Wil

[Thrasher]

Is the LR TB center 3/4" higher off the ground than RR? Does this make sense? Has the "squareness" of the TB support tube been determined relative to the chassis?

Yes, the LR TB center was about 3/4" higher on the LR. I don't know if it makes sense, but if my front end is evenly adjusted, then it does make sense that (in a square car) the back end should also be even - provided I don't have the back end jacked up slightly to one side. I'll try using a piece of wood on my jack that contacts the engine case right on the center. My jack has a fairly large pad that doesn't allow me to say I'm precisely centered. It wouldn't take much at center to represent 3/4 inch out at the fender.

Has the "squareness" of the TB support tube been determined relative to the chassis?

Not by me. I'll check this with a carpenter's square on both sides.

I will also check the wheelbase measurements and report back.

It may be a while before I can get the car on a lift to measure diagonals. I'll try to do it by crawling under the car with a helper in the meantime.

I didn't read the whole thread, but didn't recall if front suspension bushings were refreshed.

I don't see anything in the work order indicating any bushings were replaced, and I did not replace them, so I'll assume they're original. They are not plastic, and appear to be OE rubber.

Also, another update. I drove the car a little more last night and the rears settled in to the 24- 24 1/2 range, but the front is still way high. I'll try lifting the front to a tripod at center and see if that changes.

I guess that proves that my rolling back and forth isn't sufficient to settle the suspension. I may have some binding with the new Neatrix bushings and/or shocks, since I've only driven them about 150 miles.

Thanks again,

Craig

[Wil Ferch]

Two things...
1.) It appears you need to drive some miles before you get the suspension to settle out...rolling it a bit fore/aft in the driveway looks like it won't cut it.
2.) Even with the Neatrix bushings....look to see where the center bar is located relative to the springplate hole...is there a common, concentric "gap" all the way around, as found in the pics of this thread?

Should I replace my shocks? ('85)

If not, then this could explain a portion of the 3/4" apparent torsion tube height difference....that's still a lot. I'd check in that area....

Wil

[Thrasher]

Wil,

I know exactly what you're talking about. Here's a "before" pic of mine:



You can see how the rubber had flowed to the lower part. I was getting metal-metal contact on the spring plate/torsion bar cover when I hit bumps. The Neatrix have eliminated that.

I'm at work now and can't get an "after" pic or the measurements, but I'll check tonight.

I'll also triple-check my garage floor for level. I leveled it using a water tube level and VCT floor tiles.

From now on, I'll definitely be doing the "up the street and back" routine to settle the suspension.

[Rot 911]

Originally posted by Thrasher
Yes, Neatrix bushings. But no, they were not glued in. The angle was checked with no load on the spring plates, before any twisting occurred. KurtV can you verify this?

That is correct. I have done several height adjustments on 911, all the same as we did yours, with no problem!

I think you need to break this down to figure out what is happening. Right now I would forget about the front end and concentrate on the rear. Set the ride height at 25" and see what happens after driving for a day or so. If the rear end settles more than 1/4" I am going to guess that your rear shocks are leaking. If they hold steady then adjust the fronts.

[Thrasher]

I'll try that Kurt, but right now I can't get the rear up to 25" with the fronts are sitting so high at their current setting (which are correct when using the tripod and no influence from the rear suspension) without doing a rear t-bar reindex.

So, I have a real chicken and egg thing going. Since the fronts are easier to adjust, I can try dropping them down to bring up the rears. Hopefully that'll do it, because the rears are adjusted as high as they'll go with the eccentrics and I'd rather not reindex the rear t-bars only to find out it was unnecessary and then return them to the original settings.

Plus, I trust what KurtV and I did on setup of the rears. The only thing that concerns me is that we did that with the fronts not adjusted correctly and it's possible that led us to an inaccurate rear setting. If I could do it again, I'd say we should've removed the front wheels and done the tripod on the front crossmember when indexing the rear t-bars.

[Rot 911]

Craig, I am sure the tripod method works, but to be honest I have never done it that way.

[RoninLB]

Originally posted by Wil Ferch

- the tripod method is actually a factory procedure,

great.

I couldn't find it in the Workshop Manuals. Do you know where it's located ?

[Wil Ferch]

RoninLB:
I recall BA giving someone a specific response on this with pics and the factory "tool"...prolly in Excellence.
I have the manuals...I'll check and report back as time permits....

Wil