dr bob

I carefully read Cap't Earl's alignmnet instruction, and decided to make a laser fixture that's a little easier for the toe check.

The end pieces are 1.5" aluminum angle stock, 7.5" long each. The center section is 21" long, 2" extruded aluminum square stock, 3/16" wall, for stiffness and convenience. The laser levels are H-F specials, bedded in 5-minute epoxy.

The biggest part of the fab time was getting the lasers zero'd in. I built a holding fixture, and placed an aiming target grid at the other end of the garage, about 45' away. Found that the lazers were close in the vertical but way skewed horizontal. The vertical was corrected during the bedding process in the epoxy, while the horizontal was corrected by turning the laser on the mounting face. They are now within 1/32 of parallel in either plane at 45'.

Once the glue dried, they were bungied to the wheels and leveled. I used a carpenter's square to transfer the beam center to tape marks on the floor. Then a tape measure and a little bit of calculator gave me the readings. I simplified the calculations some for the trigonometrically-challenged: With readings taken 86" apart (front-to-back), 1/8" of difference equals 15' (fifteen minutes, or 1/4 of one degree) of toe. To get the toe at 45 minutes per the WSM, I made marks at 30"and 116" in front of each wheel. Look for 3/8" narrower at the outer marks and you have it perfect.

I took a hint from the camber instruction, and used the plumb-bob and dril bit method of calculating the angle. The same laser bracket, rotated 90 degrees on the wheel, made the measurement easy and repeatable. I didn't use the slide plates though, so I had to roll the car out and back after each camber adjustment to let the tires move on the floor. The theory is that you are measuring from the wheel so it shouldn't make a difference, bit it's better to let any tension in the tire relax for consistent results.


Thanks to Earl Gilstrom for the inspiration and all the tips and reminders on his website.

H2

Very good info. Thanks, Bob

Harvey

mark kibort

i have one even easier

take a level and push it against the front and rear of the wheel, mark the ground.

do the other side.

move car back and measure the front marks to the rear marks.

1/8" differnce works out to be near .25 degrees. width is 72" or so, and the formula is this.

lets say you get 1/8" difference front marks to rear marks total distance between them. toe would be 1/16" divided by 18" and then take the inv-Tangent of that figure and get the invidual toe in degrees. wala!

dr bob

Turns out I am math-challenged on this. Pay no attention to the man behind the curtain... 1.125" at 86" is the correct number. Tangent of the angle (in degrees) times the distance between the marks.

MK, your post made me get out the calculator and verify my numbers. Thanks!

UKKid35

You didn't mention the one critcal component which most of us may be lacking - the perfectly level garage floor.

dr bob

I don't think it needs to be perfectly level as much as it needs to be flat. Using the carpenter's square, I lined up the lasers so the beam is at the same height from the floor (about 12" on mine at the center of the wheel) for both the close and further readings, and the effects of static caster/camber on toe measurement appear to be virtually eliminated.

I guess I need to do the Gilstrom procedure with the water level and pads to verify my readings, and certainly before I start charging for 928 toe-in adjustments anyway. In the big picture, I can easily pay for a set of slide plates for a fraction of the cost of the tire wear avoided. When I get home again...

Ed Hughes

Why can't you shoot the lasers to some plywood or poster board at the front, and then at the rear of the car. Setting them at equal distance from the wheel centers. Mark the dots, measure between the front dots and the rear dots, and take the difference in measurements between the front shot and the rear shot to get your toe?

dr bob

Ed--

You can do exactly what you describe. That's the method MK suggests, but with the measurement points further apart. It works if you know how far the two surfaces are from the laser, so you can work out the angles from the two distances. The laser mount needs to be rigid if you don't want to move the car during the process.

Many folks use string instead of lasers, although that isn't quite as much fun.


My idea was to make a set of tools that can be used relatively quickly, with accurate and reproducible results. The two lasers are on supports that are quickly attached to the rim edges with bungies. After that it's a square, some painters tape on the floor, and a tape measure. After spending a couple hours getting the lasers perfectly zero'd on the brackets, the actual measurement was really anti-climactic; It took less than 10 minutes to get the base measurements and calculate angles, make two corrective adjustments with measurements in between, and close it all up ready to drive. Can't do that with string or laser, with the multiple differential calcs needed with the somewhat flexible fixtures that some are using.

One is no more or less accurate than the other, although the fore-and-aft method that Earl Gilstrom describes will cause the rack to be centered in the car and the wheels to be centered at that point too. That's a decided advantage, especially if the car has had damage. My lasers sit far enough out from the wheels to allow them to ce centered by looking backwards and getting them centered up on the rear wheels, using a scale to measure the beam to wheel face dimension and make them the same.


Great inputs and suggestions! Keep 'em coming!

mark kibort

am i missing something:

i calculate 1/16" from the front of the rim to the rear of the rim differece . if the distance between the dots is 18" thats :
.0625" / 18" Inverse Tangent = .2 degrees. (thats each side) this is to say that you will probably have 1/8" difference between both the front and rear tires. in otherwords, this would be total toe of .4 degrees.

Now, if you are shinning a laser on the wall in front and those dots are 86" away and you start from whatever the total toe us, the value you get is not really relavant, as you have to know what Zero is.
but, you could be 1" off from measureing how far the lasers are apart at the wheels at 86". that would be .33 degrees each wheel, or .66 degrees total toe.

I might be missing something how the lasers are setting up to measure the toe.

Its no different than how i measure camber at the track. put on a level, and measure the distance at the top of the rim vs the bottom off the rim compared to vertical. 17mm is about 2 degrees camber (about 3/4" to make the level pure vertical)
17mm/482mm INV Tangent= 2degrees camber. (or .7"/19")

Mk

borland

Make sure you calculations are the correct. I double checked mine a few times before getting them correct. Since my two HFT laser levels were slightly different in calibration, I have them labeled #1 and #2.





Dual tick marks on gage are for laser #1 or #2, so I can mix and match using them on both sides of the car.

mark kibort

I dont understand what you are measuring here.

Ive double checked my calculations. opposite/adjacent legs are the tangent. since you know only the legs and not the angle you take the INV tangent of that ratio. on an 18 vertical line, which is "adjacent " to the angle you are looking for, and the distance the hyp is off the adjacent is the "opposite". You then are able to find the angle (camber or toe) by taking the inverse tanget of this value.

I think i still remember that correctly. someone chime in here if im wrong

Mk

dr bob

Mark--

Draw a line between the two front wheels, another line parallel to it at 30" forward and onother line at 116", 86" away from the first. Think trapezoid.

Mount the two lasers in the wheels, and make the beams parallel to the floor.

Using a carpenters square, find the point on the floor where the laser is directly above the first line and the second line, on each side. Measure the distance between the marks on the 30" line, and record it. Measure the distance between the two marks on the 116" line and record it. .75 degrees is 1.125" difference between the two. The distance at the 116" line needs to be 1.125" smaller than the distance at the 30" line. Formula is 86 * tan(.75) for the 45 minutes of toe-in spec'd, right? Help me out if I'm using the wrong formula. Is toe-in measured per wheel or total? I'm thinking the WSM spec is total.

I'm using the same math you are, but you are backing in to the result I'm starting with. As you suggest, 1" of difference at 86" separation is .33 degrees per wheel, or .66 total. To get to .75 total (the spec in the WSM) that one inch grows to an inch and an eighth. You start out with a difference (1/16 * 2) and a space (18") to discover the angle (.33 * 2). I started with the target angle (.75) and the space (86") to discover the difference (1.125")


I'm still chasing a problem that seems to be with loose rack bushings. I pull the wheels off and I can see the rack housing going up and down in there as I load and unload the tie rods, so it needs at least a set of spacers to limit vertical travel. No reason to try to get good toe settings if the rack is moving, but at least I can see where some of the problem is. More when I get more time to work on it.

Ed Hughes

Another aid here is to use the internet for all it's worth. After beefing up my 911's springs (torsion bars) recently, I did my first alignment. Here's an online angle calculator. http://www.1728.com/trig.htm

All you need is two known sides, which you have here with this method-it does the rest.

And to think I took a couple of semesters of Calculus in college. That was time well spent.

mark kibort

the problem is what with this calcuator is that it wants 2 sides, but not the adjacent and opposite sides. Or, a side and a angle, and we are trying to find out the angle.

thats why, just mark two points just below the wheel on the ground! its SIMPLE. think trapazoid as Bob said. the angle is the distance the tires are toe'ed in or out, divided by the width of the rim. (or wider if you want)

that number *INV TAN and you get an angle. either camber or toe, it doesnt matter. totally saves you the effort in to mounting lasers to wood, calabrating, measuring many data points infront of the car, etc etc.

Ive done my own checking of toe and camber for years now and on the hunter machine it is within 10% of their values. if you are worried about a non level surface (not really an issue for toe, more for camber) just do this measuremet and calculation and then turn the car around and do it in the opposite direction and average the two calculations.

Mk

mark kibort

Man, you are reallly going at this the LONG way!!

but you are on the right track.

I had that bushing issue, and i used a belview washer to fix it. it doesnt take much. when had the time, i did them all with the the new bushings.

Mk