Several people asked how I do my alignment at home, so here goes:
I use a 6' Carpenters level to find a level spot (side to side) in my garage. If you cannot find one, use masonite shims under in the low spot(s) to make one. Most garages slope out for drainage, but this will not affect the alignment as long as it is level side to side. Set all 4 tire pressures to your normal pressure (~35 psi for street tires). Make sure the inside is relatively empty of heavy items.
I have a castor/camber gauge that is just a level that fits on the wheel, and reads off in degrees. They go for about $70 at any of the racer supply stores. Or just use a regular level with blocks attached to fit on the wheels. With the regular level, you will need a scale to read off the distance from level, and convert that to degrees. (For a 17" wheel, 1/2 degree is about 0.15").
How to Measure Castor and Camber: Use the level or castor/cambor gauge to read the camber of all 4 wheels. Camber is the tilt in or out looking from the front of the car. Write these numbers down. Negative camber is the tire/wheel tilting inward at the top. For the front, we need to measure castor. To due that, turn the wheel full lock to the left, and then measure the camber on both L and R wheels. Then turn the wheel full lock right and measure the camber. Subtract the two left wheel camber numbers and that will be the left wheel castor setting, and the do the same for the right wheel Note that you really want to turn the wheel +/- 20 degrees, but full lock is real close and much easier to duplicate. Also, the actual castor setting is not critical, but any difference side to side is since it will make the car pull to the side that has more castor. Toe must be measure/adjusted AFTER castor/camber is adjusted. Recommeded Settings: The follwing Settings are only a guideline, and I offer no warranty expressed or implied:
Street:
How to Adjust: For autocross settings on the late model, just jack up the front of the car, and remove all of the shims from the upper a-arm. This will give you about 1.1-1.3 degrees camber, more if your car is lowered.
For street, most Vettes come with 0.0 to + 0.5 degrees camber, so you probably want to remove some shims. Pulling out the same number of shims from each side of the a-arms changes only camber. Pulling out only shims from the rear of the a-arm increase negative camber and increases castor. The big shims are worth about 0.25 degrees (roughly), and there are several smaller sizes. For street, I would worry more about getting each side the same than the actual number. Try to keep the camber with 0.2 degrees, and the castor within 0.3 degrees side to side to minimize pull. For autocross, I would worry more about getting the most camber, and I accept more variation side to side since I want to maximize traction, not make the car feel comfortable on the street.
There is a chart in the shop manual you can follow, but it lets you go farther apart than I have stated. (It is really to let them do fast alignments within "factory specs")
In the rear, you have to remove the wheels, then loosen the inner lower control are bolt (185-ft-lbs), and rotate the bolt to increase or decrease camber. The washer is eccentric, moving the arm to the outside of the car increases camber, moving to the center of the car decreases camber. Be sure to Torque the bolts back up to 185 ft-lbs. Otherwise, these bolts can slip, changing your alignment. My torque wrench only goes to 150, so I stop there, but I check mine every few months, and I HAVE had them slip before.
The back is tricky. Use small increments. The lines on the washer about about 1 degree each, and there are lots of them, fooling you into thinking you need to move the bolt a lot. A little will do.
After you change Castor/Camber: Once you have changed your front and rear camber and front castor, put the wheels back on and drive around the block. Then measure again. This is an iterative process. You probably won't get it perfect the first time. This is why it takes a long time. Your local $29.95 guy just makes sure you are within factory specs, which are faily wide. Get the castor camber to where you are happy before continuing on to the toe.
Toe: Toe is the easiest to adjust, but must be done after the castor/cambor is changed, and you have driven around the block.
VERY IMPORTANT: If you jack you car up at ALL, you must drive around the block to settle the suspension before measuring castor/camber or toe. Otherwise the ride height is off, throwing all you measurements off. This is the single most common mistake I see the shops doing, not settling the suspension of the car. Pushing up and down on the fender of a Vette won't cut it, it is too stiff, and the tires are too wide. Drive it around the block.
For the front toe, I just use a steel tape measure. Measure the distance between the two tires from the front and then the rear. Subtract them to find the toe. Use the exact same tread front and rear, and make sure the tape is not hitting any components under the car. This takes two people, but my wife does not mind. Make sure the wheel is straight before you decide which side to adjust. You can do the front toe from under the hood. Just loosten the jamb nut on the tie-rod end and turn the steering arm to adjust. After you adjust, drive around again before you measure.
For the rear, you can use the above method in a hurry, but that is not really accurate enough. Since the rear wheels don't turn, you really need to measure each side independently. I use 4 jackstands, two on each side of the car, with a long string tied between them parallel to each side of the car. Note to due this right, you really need to find the centerline of the car by measuring from the suspension pickup points. I cheat, and just measure to the center of each wheel. Remember, that the rear track on a late model is 0.8" wider, so leave 0.4" more distance from the front wheels than the rear. From this parallel string set at the height of the center of the wheels, you can measure the distance from the front of the wheel to the rear. The difference is the toe in/out. I use the wheels to measure, not the tires. The specs I gave are at the tires, so you might have to adjust a little depending on the height of your tires. Once you have gone to the trouble of setting up the string, you could just as well measure the front toe in also. That might be easier to get the wheel straight.
To adjust the rear to, just loosen the jamb nut on the tie rod ends. You will probably need some vice grips or plies to move the rear toe rod since it is not machined for a wrench, and it is a tight fit near the mufflers. I do it without jacking up the car, but it is tight. Once you adjust the toe, you have to drive around the block again before you can measure to check the results.
In Conclusion: This process will take at least 2-3 hours, and may seem tedious, but it will give you an accurate alignment, plus you can change your own settings. I adjust my suspension every few months. I use a tire pyrometer to check tire temperatures, and try to keep them even for autocrossing. The settings will very by tire brand. The autocross settings I gave are for BFG. Yokohamas like more camber, but it is hard to get more unless you lower the car. If you are serious about doing it, I would recommend the camber gauge. But I used a standard level for years before I bought my camber gauge. You do *NOT* need a $40,000 computer system. Patience at home will be more accurate than a fancy alignment machine run by a rushed operator whose only goal is to be within the +/- 1 degree stock specs.
The most important setting for feel/handling is toe. Next is camber, and last is castor. More castor give better high speed stability at the expense of steering response. Differences side to side in castor, and too a lesser extent, camber, is usually what makes a car pull. Toe can do this also. Rear toe out is dangerous. The stock Vette does not have enough front camber to make it understeer, so it is safer for the average driver. My specs should get a street vette closer to neutral without giving up high speed stablility and without hurting tire wear too much.
I hope this was not too long. Good luck,
Chris Teague '90 Vette (ASP) teague@us17503.mdc.com