View Full Version : Alignment Questions

08-21-2004, 12:05 PM
What is the best way to economically align my car? I would like accurate tools without spending too much. I would also like to be able to use them to align my rear axles if practical/possible (that way I can shape the tubes as needed per the discussion on "Axle Flange Alignment" in the old forum within the "Suspension" section). I will post this in "Tools" also...

Jeff Andre'

08-21-2004, 12:22 PM
I've heard that some string, long 2x4's, and a level work. I just don't know how to explain how to use them......

Q ship
08-21-2004, 04:11 PM
Jeff, I have seen a couple of very informative posts over at CC.com(suspension forum), you could try searching there-or (better yet) maybe Norm Peterson will weigh in here..he had very good info and tech on doing this over there. I'm not far enough along to get up to speed on it yet, but I really like the idea of doing it myself.

David Pozzi
08-21-2004, 08:12 PM
Here are some alignment links I had saved.
http://www.smartracingproducts.com/pdfs/SmartCamber%20Manual%20Rev7.pdf SMARTLEVEL MANUAL SHOWS CASTER CALC.
http://www.smartracingproducts.com/ProdCat/AlSuTool/alsutools.htm SMART LEVEL AND CHARTS


Norm Peterson
08-23-2004, 04:33 AM
Jeff, I have seen a couple of very informative posts over at CC.com(suspension forum), you could try searching there . . .MFE has also posted some DIY alignment info on both corner-carvers and on corral.net, and I think a google on 'DIY Alignment' will turn up a page by Cal Sanders for some additional thoughts.

Here's mine:

The most important word is PATIENCE.

Find a level (or at least flat) surface, inflate your tires to where youíll be running them, and load the car approximately as it will be driven. If it isnít perfectly level, you can either shim the low wheel spots up to level or correct your measured angles once you know how far out it is. And at least simulate the driverís weight with something like barbell plates.

For a number of years, all I needed was a carpenter's 12" combination square with a bubble level in the handle, a small scale that measured in 0.01" increments (it was just something I had; 1/32" graduation is probably sufficient for most work). Plus 4 jackstands, two lengths of black thread, a plumb bob (or something that'll work like one; a church key on a thread will do in a pinch), a steel tape or two, and a calculator that has trig functions.

Camber is measured by placing one end of the C-square against the wheel rim, moving the other end until there's "zero bubble" in the level, and measuring the gap at the other end. Since the wheel is somewhat larger than the 12Ē C-square is long, you'll be a few inches ahead of or behind the axle centerline. I normally took measurements at both locations as a check on my work. Be sure that the square is perpendicular to the pavement as seen in side view. Then a little math and use of either the arcsin or the arctan function (the difference is negligible at the magnitude of the angles you'll be working with) will give you the camber angle. Or, since it's close enough to 0.15* per 1/32" gap over the 12" length of the square's ruler, you can use that conversion for most work.

Eyes that now appreciate reading glasses for close work and a desire to simplify the math still further led me to fab up a caster-camber gauge that uses a dial indicator (around $30 plus the dial indicator) in place of the C-square. There is a pic link on the first page of this thread (http://corner-carvers.com/forums/showthread.php?s=&threadid=13211&perpage=40&highlight=Wheel%20alignment%20tech%20long), and some full-size pics on the second page (warning to unaccelerated dial-up users about page 2 load time). Welding was held to an absolute minimum to avoid distortion, so itíll never win any beauty contests.

Caster is most easily determined by taking camber readings with the front wheels turned right, then again with the wheels turned left the same amount, taking the algebraic difference and applying a factor. This factor depends on the steer angle you use. If you can get 30* steer out of the front wheels, this factor is 1.00. At 14.5* (a much easier angle to obtain), it's 2.00, a 20* steer angle uses 1.46 as a factor (meaning that SmartCamber's 1.5 factor is pretty good, being less than 0.2* off in 6* caster), and the 1.5 factor actually comes up at 19.4* steer. Thereís a discussion of the general solution here ( http://www.hunter.com/pub/undercar/2573T/steer.htm) complete with exact formulae, but the factor ends up being pretty close to 0.5/[sin(steer angle)]. FYI, what that SAE paper identifies as 'toe' (T1, T2) I've been calling 'steer angle' to avoid confusion with that other alignment setting.

Toe is measured from the strings, stretched over the jackstands and set to be parallel to the car centerline. If you're a little off, there won't be any problems with total toe, though if you were going to get into measuring rear toe and thrust angle they would be off slightly. Anyway, this setup requires some patience. Initially, set the strings to be the same distance off some equivalent left and right side chassis references. Working off the wheel centers will work if all you're concerned with is front toe but will involve more math and/or offsetting the strings unequally if your rear axle isnít quite centered and you want to measure rear toe and thrust angle. Measure the distance between the strings with the plumb bob and the steel tape(s) in front of and behind the car. Adjust both strings equally until the distance between them is the same at both ends of the car.

Once the strings are parallel, you measure between the string and the wheel rim at the front and at the rear of each front wheel using the same little scale. Measure the distance between your measuring points on the wheel and you can now either calculate the toe as an angle or scale it up to the outside tire diameter to get a toe measurement in inches. That's toe per side, and may be either 'in' or 'out'. Total toe is the algebraic sum of these angles (or inches), considering toe-out to be of opposite sign to toe-in. I think the industry convention is + for toe-in expressed as an angle, BTW.

If your measurements are reasonably close to your desired settings, the sequence of adjusting things is caster, camber, and finally toe. If you're way off where you want to be, it's probably easiest if you roughly set camber, set caster, go back to camber, and then do toe. Then go back and check everything. This does get easier with a little practice.

There is a mathematical solution for setting caster and camber in one shot, though you need to know precisely where all the pivot point centers are in 3-D space relative to one another and how the adjustment moves them (likely at some skew angle). Sometime I may attempt a spreadsheet solution, but it's not a current priority. And you still need to go back and check.


08-27-2004, 04:50 PM
Thanks David and Norm,
I do have more time than money so the patience is kinda forced on me. Plus I get a week off every month so that will be the time I will tackle alignment stuff. Sorry it took me so long to respond, I used to do 99%+ of my forum viewing at work but this new forum is not allowed by my corporate WebSense program :comp3:

Jeff Andre'