Rear suspension/wheelbase set up

[Fastmax32168]

So I guess my whole car is built crooked. If I make my adjustable rear lower control arms the same length my wheelbase is about 1/4" longer on the drivers side. I guess that is the way it came as I have never found any evidence it was hit. I can get the wheelbase identical on both sides by adjusting the length of the control arms and offsetting one tire slightly to the rear and one tire slightly to the front. But now I have different suspension arcs on the left and right side due to the different length lower control arms. Is one of these evils preferable over the other?
Thanks
Roy

[cjbiagi]

I venture to say most passenger cars are not identical on each side. Part of the reason may not have anything to do with the rear of the car but rather the front. As you adjust the caster and camber you end up moving the spindle and therefore the wheel and tire assembly. Many times the cams or shims required to get the alignment correct may be different on each side putting the spindle in a slightly different position. Unless everything is perfectly squared when built there is bound to be some side to side differences if you look hard enough. I would try to make sure the rearend is squared in the chassis and then if needed move the entire rearend forward or back to center the wheels in the wheelwell. To think these old chassis are perfectly square is highly unlikely, even when they were new. If you look in a shop manual there are usually reference points to refer to rather than just measuring the wheelbase.I would think that is a more accurate way to figure out how the arms should be adjusted.

[Fastmax32168]

Clyde, As usual you are correct. I did not actually measure the wheelbase although I did use that term. I measured from several frame holes to the rear axle and from the front A-arm mounting points to the rear axle. The difference of 1/4" actually appears to be in the mounting holes for the lower control arms. The one on the drivers side is 1/4' further forward than the one on the passenger side. Making the lower control arms the same length pretty much centers the tires in the wheelwells. Making the measurement to the frame hole on each side the same places one tire forward and one tire back.
Roy

[chevyart]

roy usually the 2 large bolts that mount the front control arms are good, accurate measuring points. guys that do rear backhalves will plumb down from those bolts(center of them) and very carefully make a mark on floor(USING PLUMBOB) and connect those two marks with a chalkline and measure to rear axels to line up the housing. they also go to rear of chassis and find common points and do the same as front, find center of front and rear lines, and then make a centerline for whole car(front to back). sometimes you can find some good reference points under the rockers panels(jig holes) where car rides down the assembly line. any chance you lost a little measurement with slack in your tape measure, or maybe just a little off where you measured from. just some food for thought. let us know what you find art

[cjbiagi]

Using the front lower control arm bolts would be fine if they weren't mounted in eccentric holes with offset cams. As you adjust the cam bolts for the front suspension alignment you are also moving the centerline of the bolts. There is about a 1/2" swing in those bolts. Reference holes in the frame would probably be more accurate as that is what some of those are designed for.