Excess Rear Wheel Camber ????

[nkemp]

problem with using the fender as a reference is that they are not only different from car to car, they are different from side to side on the same car!

argh!!!

[DMCMW Dave]

- Driver side 1 1/4" difference top to bottom of the wheel
- Passenger side 1 1/2" difference to to bottom of wheel
- Crossmember is about 4 1/4"off the ground
Tires: 245/60 33PSI

That's an insane difference.

BTW with all the same settings, with the car settled, I'm at 5-1/2" frame to floor.

Strange things are afoot here. . . . .This is about where I'd start making comparison measurements between two cars in the shop. Just to try and find the difference whether it's in the frame, control arm mounting points, or ???

[nkemp]

In terms of camber, the rear suspension is pretty straight forward. The things that can affect it are:
- The carrier (but I believe carriers didn't vary)
- Control arm (upper and lower) length. (there are unsubstantiated rumors they varied but the old and new ones I have are the same length. Caution : Sample size is N=1)
- Mounting position of the inboard control arm points. The bottoms would be easy to measure. The tops, not so much.
- The shock lower mounting cup height
- The shock Upper mounting height

The last two are important since it seems the suspension does not move a parallelogram.

I now wonder about the rubber bushing on top the springs ... do they compress? Would it make that much difference? Would an additional spacer help?

I've seen many lowered cars that look great and do not have the adjustable control arms. Camber is slight, not nearly as bad as mine.

EDIT: ... One more thought (scary thought) is that the shock towers are moving inwards at the top. The crossmember should minimize that ... but a thought none the less.

[nkemp]

That's an insane difference.

... 5-1/2" frame to floor. ...

Due to variations in tires (wear, pressure, design, etc) I can see a little difference in ride height. Maybe 1/2" or more but that is only a guess. Tread wear could be 1/4" or morealone.

But yes, mine is way off and thus the investigation.

[Rich]

The latest geometry you report shows massive neg camber, something on the order of -5 deg., which I'm sure you can easily see is way off.

Your frame height is way low even though you're running what we think is a "good" shock height from bolt to spring cup. Let's guess something is wrong in translation on that attempt.

The new 4.25in frame height is the primary cause of the negative camber now.

Recommending to go up ~1.25in. on the shock collars (Dave's 5 13/16 plus 1.25 is about 7.0in) so you're close to 5.5in. rear x-member height and see what you get camber-wise. Guaranteed it'll be closer to spec but may still be excessively negative.

Set aside the linkage/parts issues til we all get numbers we understand.

[nkemp]

Rich, I'll adjust as you suggest but it is likely a tomorrow project (need to change mode from DeLorean mechanic to family member But in the past I did have them 7.5" from center of lower mounting bolt to top of white bushing/washer/spacer/disk- Using a square on the pavement, the difference in distance to the square from the top of the rim to the bottom is 1 3/8" (passenger) and about 1" difference on the driver side.

That said, those measurements were not that good so I want to remeasure them on the cement and more carefully once I get them readjusted.

Rich ... Your VIN is not that far from mine. One would assume they are similar.

[DMC5180]

Also weird, your 245/60 tires at 33 psi should create added ground clearance. Makes me wonder if you have the wrong Coils on the shocks.

Measure the weight on wheels coil length if you can.

[nkemp]

Yet another great day to get under the car ... The shocks are now set at 7" bottom of cup to the center of the lower mounting bolt:



EDIT: I tried using the table function just above this and it does not display. AND the forum software deletes extra spaces so follows is sorta a table.

Cup height .........Crossover height ..........Driver's difference .......Passenger difference
Cup height: 5 5/16" Crossover height : 4 1/4" Driver's difference 1 1/4" Passenger difference 1 1/2"
Cup height: 7" Crossover height : 5 1/2" Driver's difference 7/8" Passenger difference 1 1/8"
Cup height: 7 1/2" Crossover height : ??? Driver's difference 1 3/8" Passenger difference 1"

Notes:
- A 1" deviation across 16.1" (distance from measurements) is about = 3.554° = 3°33'15" = 0.062032 rad
- There is a lot of tire wear, especially to the inside, so it is possible that with new tires, the frame crossover height would be higher than above numbers.
- The 7 1/2" measurements are more suspect and I'm getting better at the measurements as I go

FYI ... IF the spring height is adjusted unweighted, then driving the car is very important. I drove it about a mile and the rear crossmember height dropped 1" (6.5 -> 5.5").

[nkemp]

Also weird, your 245/60 tires at 33 psi should create added ground clearance. Makes me wonder if you have the wrong Coils on the shocks.

Measure the weight on wheels coil length if you can.

I agree with "weird"!!! And I's swear it has gotten worse over the years but it is like the frog in the boiling water.

Weight on wheel Eibach spring length is about 9". I put the longer shocks on the rear (the fronts are not yet installed and uncompressed they are about 13")


FWIW … I have an original set of springs (not from my car) and they measure about 16" uncompressed and that is the length of the uncompressed set originally on my car and removed after maybe 50,000 miles. I didn't measure the uncompressed Eibach springs before installing

[David T]

At this point I would be examining the frame. If it is bent or rotten all bets are off. I know the front can rot enough to destroy any attempt at alignment, maybe your rear engine cradle is rotten or was in some way previously damaged and then repaired incorrectly. Refer to section R:02:XX in the Workshop Manual. What makes me especially suspicious of your frame is the fact that you can't get it near the same side-to-side. On most cars, even if the specs are way off they are at least consistent side to side. You have to consider tire wear but severe camber will negatively affect braking and handling. As for the equipment to do an alignment, you can do a good job with rulers, sticks, strings, levels, and chalk. You can do it much better and a lot faster with a laser guided, computerized alignment rack. I seriously doubt any substantial difference between early frames and later frames. The frames were built in jigs and they must have been the same jigs for the whole period of production. The only difference I have every seen in frames is manual vs automatic.