Bent Chassis or???

My beater 91miata has a hard pull to the left, at some point in it's life there was a wreck on the front driver's side corner. My friend that I bought it from has owned it since the late 90's and is not the culprit. The only visible damage is by the headlight bucket some of the metal is wrinkled and the nose piece in the top corner is slightly deformed. From my keen sense of deduction (sic) I can tell that this is where the damage occurred. I've measured the wheelbase and it seems that there is an appx. 1/8 in. difference, with the driver's side being shorter. Is there a grassroots way to determine if the chassis is bent or if it is a control arm or other various suspension piece.

I know on my honda after a vicious curbing by an old g/f that it didn't affect the chassis but did bend a lower control arm. Being that this miata was in some type of accident, I'm leaning heavily towards the chassis not being straight, but would love for the only problem to be the control arm. I'm really wanting to do a cheap restomod job on this car, but I don't want to sink to much money only to find out that it was pointless. I know that it will never be perfect, but I figure if it can be reasonably straight an alignment can dial out most of the bad habits.

Miata control arms are known for bending. Why don't you jack the front of the car up and (using jack stands) measure both front lower and upper arms to see if they are an exact mirror image of each other. dimensionally?

Why not try to measure the distance of something fixed to the chassis (or some distinct part of the chassis itself) on either side?

do you have improper wear on one specific tire? like a front? I think my chassis is bent and i have horrific wear on my right front with positive camber and the left rear tire is practically brand new... we will see after a whole new suspension upgrade...

I just had the alignment set, the toe was 1/32 each side, camber was equal, but caster was 3/4degree different left to right. When I bought the car last summer, the left front was worn more on the outside, too much toe in. I had it aligned 3 or so months after I bought it and the tire wear seemed to be even. I've been pretty good about looking at the tires since I suspect something is up, and they seem to wear fine.

I live at an apartment complex and while car repair isn't forbidden, I try to be nice and keep all 4 wheels on the ground. While I live on the redneck end of town, I live at one of the nicer complexes. I'll try to measure some fixed points while I'm at my parents fixing their tiller. Does anyone have a link or pdf of the fsm or at least chassis measurements for a 91 miata?

I've seen a couple of Miatae which have walloped curbs or similar and they had bent the underside of the bodyshell where the rear 'leg' of the front subframe bolts to the floorpan. It was pretty easy to see once the carpet was puled back, the mount bolt's plate etc was pushed up. Not insurmountable, one of them was fixed by loosening all the mounting bolts and adding shim washers on the bent side between the subframe and floorpan till it leveled out. The other had a lot of other damage (busted oil pan etc) and was totaled by the insurance company before I could snag it cheap.

On full frame cars most manuals will have reference points from which to measure. I am sure uni-body will have the same, I just dont have the experience with uni to know. The procedure goes something like this.

Jack the car up on a level surface. (you want the car level also)

At the left frontmost control arm attaching point drop a blumb bob down to the ground and mark that point. (best to remove the control arm and wrap the line either inside or outside the bolt always do it the same way at the front or rear of the boss) (make sense?)

Do the same for the left front rearmost attaching point.

(these are set points for the chassis, I hope I have explained what I mean)

Work your way back using reliable fixed points on the chassis (these are usualy notated in the manual) Subframe attaching points, rear control arms, rear subframe mounts, etc.

Do EXACTLY the same for the right side.

Now lower the car and get it out of the way.

Take a chalk line and a friend and snap a line form each point on the left to each point on the right. (you should have a buch of super emposed X's in the middle of your floor.

Lastly snap 1 line down the centre where the lines intersect. Now you have a bunch of super inposed X's and one straight line down the centre on the floor. If all is square they (the X's) should all intersect on this line. If not you can get a rough idea where the chassis is out by using a tape measure and measuring betwene each point.

You can get a rough idea if the chassis is bent on a horizontal plane (twisted) by measuring from these same points down to the floor while the chassis is in the air. That is another reason to get the car level. One or more corners will be higher than the others if the chassis is twisted.

If you dont move the car before snapping your lines you can move the centre line on the floor up to the chassis to mark the centre line of the chassis for future set up.

Who needs a laser alignment rack? You will need a fair amount of time and a lot of room to post the directions on a mesage board.

Feel free to ask questions as my explaining and spelling usualy suck.