Do-It-Yourself 4 Wheel Alignment

By Thomas Mezger

 

The art of wheel alignment is not magic or requires expensive equipment or skill.  Step one is to build parallel reference line on each side of the car, or more specifically the wheels.  Step 2 is to make measurements.  Step three is to make the necessary changes.  Step four is to re-measure.

 

MAKING THE ALIGNMENT JIG

1.     Buy two lengths of electrical conduit about 85” long.  The length is not critical must be a few inches wider than the wheel track.

2.     Using a hacksaw cut a notch approximately ¼ of the way thru the conduit near each end of the conduit.  These are used for placing the fishing line. See Detail “A”.  The notches must be at the exact location on both conduits.  By clamping the conduits together makes cutting the notches on both in the same location easier.  The exact notch placement depends on your car’s track width.  Positioned the notch approximately ½ inch wider than the axle with the widest track.  (Note: There are many ways to construct the attachment points for the fishing line.  This is only one.  The notch method is quick, easy, keeps the fishing line from moving, and is repeatable. 

3.     Cut two lengths of 25 ft monofilament-fishing line.  6 lb test is fine.  Tie loops in the ends and place around the conduit into the notch.  The fishing lines must be equal in length and a few feet longer than the vehicle.

 

SETTING UP THE JIG

1.     The car should have a full tank of gas and tires air pressure set to spec. Drive the car on to a level surface.  If necessary, shim the area under the tires with wood or floor tiles to get all 4 tires level.  Make sure the steering wheel is straight.

2.     Place the conduit on the jack stands and held into place using “U” brackets.  The hold down device should allow the conduit to be slide side-to-side during set up without having to move the jack stands. Position conduit the same distance (35 inches in my case) from the wheels then make sure the fishing line is stretched tight.  Use bricks on the jack stands to hold them down on the floor if necessary.  The fishing lines should be positioned at the center of each wheel or 1 foot off the floor.  See Detail “B”.

3.     The two fishing lines and two conduits should now be parallel from side-to-side and front-to-back. 

 

Fishing Line

 

 

 

Toe in measurement

See Detail “C”

 

 

(View from Top)

 

 

Tires

 

 

Notches in conduit are approximately ½ inch wider than your car’s track (See Detail “A”)

 

 
 

 

 

Electrical Conduit

Can substitute gas pipe, flat iron, angle iron, square tubing, or 2x4 wood.  Anything straight will work.  Attach to jack stand loosely to allow conduit to slide side-to-side for easy set up.

 

 

Jack stand See Detail “B”

 

 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Optional: 

Create centerline and set up jig based on this reference point.

 

 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

 

 

  

 

 

 

 

 

 

  

 

Cut a notch 3 to 4 inches from each end of the conduit to make placement of the fishing line very exact.

 

 

Detail “B”
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   

Position conduit on jack stands 35 inches from each tire all the way around vehicle.  Pull fishing line tight.  You may need to place a brick on the jack stand to hold it down.

 

 MAKING TOE MEASUREMENTS

For Toe-In, take initial measurements from the fishing line to the front of each rim to determine which direction to move the conduit to get the fishing line the same distance at all 4 rims.  Take the difference it track width between front and rear into account.  On my car, the rear track is 1 inch wider than the front.  See Detail “C”. 

Write down all measurements because it can get confusing.  Use a 6” machinist ruler with accuracy of 1/64th of an inch.  These are available at any home supply store.

Move the front or rear conduit side-to-side until the measurements show the LEAST AMOUNT of variance in the toe between all 4 wheels.

 

If the toe is adjusted, make sure the final toe settings are equal on the right and left side.  In other words, if the left rear is set to 1/32nd inch toe-in, so is the right rear.  This is necessary to insure the thrust angle from the rear tires is on the car’s centerline.  Drive the car at least ½ mile then recheck.   You may want to check it after a couple of weeks.

 

Detail “C”

 
 

 

  Tire cross section

 

 

Rim

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fishing Line

 

 
 

 

 

 

Measure from rim bead to fishing line.  Write down measurements from each wheel and convert to degrees using conversion table. 

 

 

MAKING CAMBER MEASUREMENTS

1.        To measure camber, make sure vehicle is on level concrete.  Use a 2-foot carpenter’s level with two bolts threaded into each end to clear the tire and touch of the rim.  Use a bungee cord to temporarily attach level to rim. See Detail “D”.

2.        If you make any adjustments, you MUST drive the car at least ½ mile then measure again.  I know this from experience.  Just rolling the car back and forth a few feet does not work.

 

Detail “D”

 

 
 

 

 

Insert shims here to zero bubble.  Then convert to degrees

 (See conversion table).

 

 
 

 

Tire cross section

 

 
 

 

 

 

 

 

 

 

Measure here

 

 
 

Rim

 

 
 

 

 

 

 

 

 

 

 

 

 

Measure on level Garage Floor.  Drive car onto stack of floor tiles if necessary.  Attached level to wheel with bungee cord if desired.

 

 

Conversion of inches to degrees

All of the measurements made are in inches (or fractions there of) but the spec’s are in degrees.  To convert to degrees, first measure the distance between the two points in question.  Then convert that measurement to the circumference of a circle.  The formula (the cymbal ¶ is Pi):  

¶ x Diameter = Circumference

 

Example:

Assuming a 10 inch diameter, then:

¶ x 10 = Circumference

3.14159x 10  = 31.41 inches circumference

 

A circle has 360 degrees, so 31.41 inches in circumference divided by 360 = .08725 inches in circumference per degree.

 

Example:

Assuming a rim toe-in is 1/8th inch over 17” as shown in Detail “C”.  The calculation is:

¶ x 17 inches = Circumference

3.14159 x 17 inches = 53.407 inches

53.407 inches / 360 degrees = 0.1483 inches per degree

1/8th inch / 0.1483 = degrees

0.125 inches / 0.1483 inches per degree = 0.8429 degrees

 

Degree per inch table:

Since nobody wants to go through the math each time, I have provided a table with the most common measurement distances.  If your measurements are not here, you can extrapolate between two points.

 

 

 

CIRCLE DIAMETER

32nd Inch

Inch- Decimal

16.00

16.25

16.50

16.75

17.00

17.25

17.50

17.75

18.00

18.25

18.50

18.75

19.00

 

 

DEGREES

1

.03125

.22

.22

.22

.21

.21

.21

.20

.20

.20

.20

.19

.19

.19

2

.06250

.45

.44

.43

.43

.42

.42

.41

.40

.40

.39

.39

.38

.38

3

.09375

.67

.66

.65

.64

.63

.62

.61

.61

.60

.59

.58

.57

.57

4

.12500

.90

.88

.87

.86

.84

.83

.82

.81

.80

.78

.77

.76

.75

5

.15625

1.12

1.10

1.09

1.07

1.05

1.04

1.02

1.01

.99

.98

.97

.95

.94

6

.18750

1.34

1.32

1.3

1.28

1.26

1.25

1.23

1.21

1.19

1.18

1.16

1.15

1.13

7

.21875

1.57

1.54

1.52

1.50

1.47

1.45

1.43

1.41

1.39

1.37

1.35

1.34

1.32

8

.25000

1.79

1.76

1.74

1.71

1.69

1.66

1.64

1.61

1.59

1.57

1.55

1.53

1.51

9

.28125

2.01

1.98

1.95

1.92

1.90

1.87

1.84

1.82

1.79

1.77

1.74

1.72

1.70

 

 

 Parts list:

1.           Conduit – 2 pieces of approximately 85” in length.  Can be ½” or ¾” in diameter.

2.           “U” shaped conduit hold down brackets.  These are screwed to the 4 jack stands to provide a convenient mounting point for the conduit but allow the conduit to slide side-to-side for convenient adjustment during set up without moving the jack stands.

3.       Fishing line.  I like 6 lb test because it is thin and stretches tight between the conduits and permits accurate 1/32nd inch measurement.

4.       6 inch Machinist ruler.  Available at hardware or home supply store.

5.       4 jack stands.

6.       Bubble level with metal frame for camber measurement.

7.       Drill to attached bolts into bubble level.

8.       Bungee cord to attach level to rim for camber measurement.

9.       Shims of various thickness (wood is fine) for bubble level adjustment & measurement of camber.

 

 

Final note:

Remember, each wheel may be on a slightly on a different vertical plain.  That is not a problem.  Body panels may not be positioned the same in relationship to the wheels due to manufacturing tolerances.  What is important is to determine the EXACT direction each wheel is pointed and not the wheel’s relationship to any other reference points such as the body.  This is why I have not used any portion of the body in measurements.

 

Move front and rear conduit side to side until the MINIMUM values of toe-in are found at each wheel and the measurements are the same from side to side for both front and rear wheels.  This will be the vehicle’s real-world toe-in regardless to the body’s centerline.    This is especial important in determining the vehicles thrust angle which is the angle the rear tires are pushing the vehicle.  It is mandatory to do a 4-wheel alignment on vehicles with IRS.  You can have the correct total front and the correct total rear toe but if they are pointed toward one side, the car will dog track and will not handle right. 

 

Be aware the track width on the front tires is different than the rear tires.

 

An option you may want to consider would be to determine the centerline of the vehicle from which you can position your perimeter fishing line.  There are many ways to do this including taking half the distance between the tires on each axle then drawing a line using a carpenters chalk line on the garage floor then center your conduit over the centerline.  On my older 1971, Corvette I did make this part of my alignment procedure but for my 1996 Corvette after taking measurements, I felt it was not a material element.

 

  

DISCLAIMER

The technique outlined in this document is provided for educational purposes and for someone who enjoys the fun of working on their own car.  It is assumed that the person who uses this document knows and understands the risks of working on vehicles.  I cannot guarantee the results.  Anyone who uses these instructions does so at their own risk.

 

This document shall be reprinted without expressed written consent from the author, Tom Mezger.