I'm doing my alignment for an upcoming trackday... Going to maximize camber, then caster, and probably do 0 on the toe.

I've got a couple of newbie questions... What bolts do you loosen to adjust camber... I did only the bolt on the lower suspension arm closest to the center of the car... And the caster is the bolt on the lower suspension closest to the center of the car and the back of the car?
Any other bolts to loosen?

I have both those mentioned loose, and am trying to bang on the suspension(tire off, on jack stand), to get the bottom suspension arm to come out,, make more negative camber, but it won't go to the extreme edge of the slot. I was just gently banging for now, but I thought I'd come check. Can you get the suspension arm all the way to the extreme in that slot,, or is something else stoping it?

If anyone has any pics or a writeup for a camaro, i'd appreciate it.
thanks,
J

 

How can you accurately measure what you are doing?

 

I'm going to use the modified level and trig... And string the car for toe.

 

Once you know just what it is that you're measuring and how to measure it, it's surprisingly simple and can even be done using only tools commonly found in home workshops.

25 years worth of DIY-in-the-driveway alignment experience.


jrummi - there is a special tool for moving the control arms, and some people have made their own versions, but most DIY'ers just use a pry bar or large screwdriver. I have no idea whether or not something's hanging yours up. Are both bolts on each side sufficiently loose without being in danger of falling out?

Norm

 

I got the lower arms to move easier by jacking them up.

Which way do I want to go on the caster... Its the rear bolt on the lower control arm,, correct? The vertical bolt,, and the horzontal one is the camber,, right? That vertical bolt seems to have an IN/Out slide and not a forward back slide like I was expecting. I guess I'll try moving the control arm out,, so that the vertical bolt is all the way to the outside of the slot. Is this right?

 

Picture the control arm free to pivot about the camber bolt (or make a little cardboard model and hold the camber bolt position fixed with a thumbtack). Moving the arm out-ward at the rear bolt position will cause the ball joint location to move forward (which increases +caster in the case of adjustable lower arms).

I suggest that you make your camber measurements off the wheel rather than the tire, as tire sidewalls may bulge somewhat non-uniformly (most noticeably at the bottom, but may elsewhere as well) and have raised lettering that will introduce errors into your calculations. Obviously, a bent or badly dinged wheel will throw things off, but this problem would mess up measurements taken off the tire as well (and has been known to escape the notice/attention of alignment techs). A carpenter's combination square with the little bubble level in the 'handle' can be used to work to within 0.15*. I do have a fairly lengthy write-up for the G-body (the uppers are adjustable and set with shims instead of the lowers by bolt clamping loads) that discusses most things in fairly general terms.

Norm

 

Where is the write up?
Thanks for the help....

 

The most important word is PATIENCE.

Find a level (or at least flat) surface, inflate your tires to where you’ll be running them, and load the car approximately as it will be driven. If it isn’t 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 driver’s 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.

Turn plates can be approximated with several sheets of newspaper, or grease between sheets of plastic or between flat squares of sheetmetal. Or you can roll the car backward and forward a bit.

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 12” 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.

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, and 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). There’s a discussion of the general solution here complete with exact formulae, but the factor ends up being pretty close to 0.5/[sin(steer angle)]. FYI, what I've been calling 'steer angle' is referred to in that SAE paper as toe; so don’t confuse the paper’s terminology 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 isn’t 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. Note that wind gusts can move the threads and throw your measurements off, so pick a calm day, or park such that the wind isn't directly hitting either of the threads.

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.

Toe is corrected by adjusting the tierods.

Caster and camber adjustment methods vary considerably, but with OE control arm suspensions you basically move the inner pivot locations of one of the arms around to change these settings. Typically, you loosen the nuts/bolts that hold the adjustments, physically move the arms to the new positions, and retighten the fasteners. You may have shims to positively maintain your adjustments, or your car’s arrangement may depend on friction and fastener torque to hold things in place.

As to the accuracy of the method outlined above, it’ll work to within about 0.1* camber with a little practice and patience. That’s comparable to the thinnest available shim for GM front suspensions, and is about as good as you’re likely to get outside of a race shop. And with a small scale that’s graduated a little finer, say to 0.01”, you can work to about 0.05* camber and below 1/32” toe tolerances in still air (a breeze will move even a fairly taut thread around enough for an 0.01” scale to pick up and affect the toe reading).

As an update, 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 ~$35 dial indicator) in place of the C-square. Welding was held to an absolute minimum to avoid distortion, so it’ll never win any beauty contests. I can take some pics. In addition to being faster, a dial indicator caster-camber gauge is more accurate (not to mention being far easier to read). You can buy C-C gauges from the various circle track supply houses for about $130 US if you don’t feel up to the fabrication.

I also have a pair of cheapie lasers that project lines rather than spots that I haven’t used yet. My next DIY alignment equipment will be some arrangement of bracketry to mount these to the wheels such that the beam planes are parallel to the wheel planes. Then I’ll be able to leave the parallel strings in the toolbox unless I’m investigating thrust angle.

If your measurements are reasonably close to your desired settings, the sequence of adjusting a suspension that has one adjustment directly inboard of the balljoint is camber, caster, and finally 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.

Norm