Laser Level method for determining Toe In.

Basically what Iím doing is placing a laser level against the outer edge of each of the front rims and letting the projection fall on a surface that is relatively close (4 feet) and then moving that surface to a point farther away (7 feet) and marking the projection again.

 I use a 2X4 board propped up on two stools as the surface and I mark the pinpoint beam projection (The red dots). I used a single board. I actually moved the car backwards instead of the board forward. 

You donít have to worry about getting the boards (or board)  in the correct position laterally because you will be subtracting one dimension from the other and dividing by two to get the average. Just keep your marks straight (which are the close measurements and which are the far measurements). If you were interested in comparing the toe in specifically on each side then you can use the laser beam positioned on the rear wheels as a means to get the board(s) in line laterally for each measurement.

My "a" dimension turned out to be 1.3125" and the distance "b" was 4' or 48 inches. So the toe in was the Arctan(1.3125 / 48)=1.556 degrees (Way to big)

The Arctan is sometimes displayed on your calculator as TAN-1

To get the toe in measurement as defined by the manual which is the distance the front edge of the tire is actually inboard from the back edge of the tire.

Sorry more Trigonometry! 

You just need to use the angle just calculated and solve the equation for "a" using 25" as the "b" dimension" (My tire was around 25" in diameter)

a=Tan(A)  X b

In My case 0.68" Which is way out of spec! it should be around 1/16"  -  1/8". I turned the adjuster rod on my front end about 2 turns and I ended up with a measurement of about 0.448 degrees (or 0.19" on a 25" diameter tire)

Here you can see that I needed to tape a couple of blocks (Purple)
 under the level to get it away from the wheel to clear the spokes
 and tire. These blocks have to be closely matched in thickness. 
The tape just serves to loosely hold the blocks in between the level
 and wheel rim surface. 

You can see that the blocks are
 rotated slightly so that I can bear the clamping force against
 the outer rim and get a repeatable measurement

Here you can "Barely" see the projected laser
 beam on my piece of wood sitting on the stool

 

Use this spreadsheet to calculate your toe-in

 

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Copyright © 2002, 2003, 2004 Rick Neves

 

 

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Last revised: June 04, 2015!

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