Strange wheel alignment problem

[Michael]

After doing the bumpsteer crossmember mod, I discovered a weird wheel alignment problem with my V8 Z: in the front, the driver’s-side wheel appears to stick further outboard than the passenger’s-side wheel. But in the back, the situation is reversed. The car has 14x7 wheels with 225-60 tires, and stock suspension components, with the possible exception of the springs (courtesy of the previous owner).

 

Making reasonably accurate measurements in the rear, I found that the left vs. right control arms do not measurably differ in length, and the distance from the control arm outer pivot (that ~8" shaft that's so hard to hammer out) to the wheel rim lip has a left vs. right difference of at most maybe 1/16". In other words, at the bottom, the left and right wheels are pretty much symmetric about the car's centerline. Not so at the top! The rear right wheel has significantly more camber than the left rear. With the rear jacked up, a broom stick leaning vertically against the tire also touches the left wheel fender lip, but is 3/4" outboard of the right fender lip! In other words, standing in back of the car and looking at the rear wheels, the left wheel is at the 11 o'clock position, and the right wheel is at the 2 o'clock position (1 o'clock would have been symmetrical).

 

With the car on jackstands, the wheels are of course hanging down, so both have high camber, but the right-side rear wheel is ridiculous. Evidently the right-side McPherson strut has a different angle between the strut and the stub axle axis! Weird.

 

At the front, the situation is similar, but reversed; using the lowest point at the wheel rims as reference, and measuring to things like control arm pivot points, reference points on the steering crossmember, and so forth, I get pretty much the same numbers. So the "bottoms" of the wheels in the front are also nearly symmetric about the car's centerline. However, the minimum gap between the coil spring perch and the inboard surface of the tire on the driver's side is about 0.5", maybe even 0.75". On the passenger side, it is almost ZERO - so that tire almost rubs! That explains the visual effect of left-right asymmetry, but it does not explain the mechanical cause. I did, by the way, switch the left and right wheels, just to make sure that there was no funny asymmetry in the wheels themselves - and there isn't any. What's going on????!

 

Looking at old photos of the car, with its original wheels and before the V8 swap, I can discern tell-tale signs of the same stuff going on. So this is not something that happened in the history of the car since I bought it - either due to the steering crossmember mod, or the V8 swap. And for what little time I drove the car after the V8 conversion, I did not notice any bias in the car's tracking. In other words, it FELT correctly aligned.

 

Opinions? This can’t be a feature of the stock Datsun design, right? Nor is it the result of any obvious accidents or mechanical damage (none that I can tell, at least). Could the spindles be bent? That might account for the problem in the front, but in the rear???

 

By the way, a NEW photo description of my car is hosted on Pete Paraska’s site (thanks again, Pete!) at http://mywebpages.comcast.net/pparaska/MichaelOlsBBZ.htm. It contains construction photos and details of the roll cage, engine mounts, etc.

[Guest Drewz]

Any 4 wheel alignment shop can do the measurements during the alignment to try and define the problem area. Could be a swayed frontend, bent fenderwell, bent strut, etc. The spec.'s versus actual readings can be compared to dramatically figure it out or you could get it measured at a frame shop. Just a few ideas!!

[johnc]

Assuming nothing is bent...

 

Sounds like the car's racked. Basically the front crossmember is pushed to the left and the rear suspension mounting points (the front and rear crossmembers) are pushed to the right.

 

For the front, unbolt the engine and support it on a jack. Loosen the front crossmember and try pushing it to the right. You mght need to use a bottle jack. Snug it up and measure to the front tension rod mounts to see if things are square. If you can get it square, buy new nuts, bolts, backing plates, and torque to spec.

 

For the rear, you first have to replace the bushings. I suggest you also check and replace the lower caps that clamp the control arms in place. They distort over time. Also, buy all new nuts, bolts, washers, and locks.

 

Assemble the rear crossmembers and control arms and lightly snug in place. Measure to some known good points on the frame to determine if things are square. Carefully tighten to spec and then re-measure. If things move, then one of the crossmembers is probably bent.

[Guest Anonymous]

Alignment Problems:

The best thing to do is to take your car to

a good body shop with wheel alignment machine.

Alot of wheel alignment shops (Goodyear,

Firestone,etc) usually can not correct if the

problem is major (such as bent frame etc). If

there's not a good body in your area, post your

alignment specifications - maybe I can give some

ideas. It can be difficult as frame alinment is

vital to good wheel alignment. Also, you didn't

mention tire wear, car pulling left or right?

 

Sunny

[Trevor]

Measuring the gaps from a broomstick to the fender lip might not be the most accurate way to judge suspension alignment. I would consider the external sheet metal of a 30 year old car the least symmentrical components side-to-side. This is Not to be critical of the condition of your car, it may "look" smooth and perfect. But professional restorers notice and remark that even Cobras and Ferraris are not symmetrical.

 

Use a plumb bob and a string. Last I head the Earth's gravity was pretty close from one point along side of a car to the other 50" away. Measure from the string to the wheel lip top and bottom. to determine that the camber is the same side-to-side.

[Modern Motorsports Ltd]

Good points Trevor, I've also found great variances in fender lip height relative to 'fixed' frame points etc.

 

Michael, have you measured it up with your wheels etc all bolted up and car sitting on the ground and rolled (ie. not just set down after being on jackstands)? You mention it's up on stands at present and typically struts don't hang down equally and can be quite different in full unloaded droop due to various binding in related joints/restrictions etc. The camber etc as Trevor comments must be done/measured loaded and 'rolled' to have a degree of accuracy for comment/curiousity etc.

 

good luck

[pparaska]

Michael,

 

(My email and web site have changed, so I editted your post to fix that.)

 

Have you measured the lengths of the strut tubes, left versus right? How about the isolators at the top of the spring/strut cartridge? Is the angle between the stub axle and the strut tube the same left to right side of the car? How about the strut tube to spindle angle?