How to Check an Alignment

Checking your own alignment only requires a few tools and some specialized knowledge.

Checking the alignment on your vehicle is a project virtually anyone can perform. There are no special tools required, just ordinary ones available at any hardware store and a little bit of trigonometry. The job involves taking measurements of the toe and the camber, both of which affect tire wear and tear, and straight-line stability and cornering. The toe is the measure of how well the front wheels are set parallel to one another. If they both point slightly inward, this is called toe-in. Both pointing slightly outward is called toe-out. Camber is the vertical angle of the wheels.

Things You'll Need

• 2 jack stands String Tape measure with inches and millimeters Carpenter’s level & cardboard strip whose length equals the tire rim diameter Electronic digital caliper

Instructions

1. Park the car on level ground with the steering wheel straight. Next, tie the string to both jack stands so it is parallel to the ground. The distance of the string from the ground should be even with the hub of the front and rear wheels. Place one jack stand 12 inches behind the rear tire and the other 12 inches forward of the front tire. Measure the distance of the string from the ground, close to the jack stands, to verify that both ends are the same distance and therefore the string is completely level.

2. Set the distance between the string and the front and rear hubs, adjusting the jack stands as necessary. The string should be 10 mm away from each hub, and it must be pulled tight between the jacks. On the front tire, measure the distance between the string and the front of the rim, and then measure the distance between the string and the back of the rim.

3. Subtract the rear measurement from the front measurement, and this gives the toe in millimeters. Plug the measurements into this handy formula to get the results for each tire: (front mm) – (rear mm) = mm toe. For example, if on the front tire, the front measurement is 9.5 mm and the rear is 10.5 mm, the simple formula yields the following difference: (9.5) – (10.5) = -1 mm toe, meaning the tire is toe-in by 1 millimeter. Negative numbers are toe-in and positive numbers are toe-out. Consult your owner’s manual for proper toe specifications. Repeat this procedure for the three remaining tires.

4. Tape the cardboard strip to the carpenter’s level so the strip rests on the bottom edge of the rim while the carpenter level stands against the tire, one end flat against the ground. Keep the end of the level on the ground, but in preparation for taking the measurement with the caliper, angle the level away from the tire an inch and a half. The bubble indicator should be away from the level zone.

5. Position the electronic digital caliper between the rim and the level. Using the level to push the caliper closed, watch the bubble indicator on the level until it is centered, and stop closing the caliper. Use this reading to calculate the camber using this formula: inverse tan (caliper measure mm / rim mm) = degrees of camber. Inverse tan, which is short for inverse tangent, is a trigonometric function used in calculating angles. For example, to fill in the formula blanks, convert the 18-inch rim to millimeters, 457.2 mm. Then suppose the caliper reading was 21.92 mm, the formula would look like this: inverse tan (21.92 mm / 457.2 mm) = 2.7 degrees of camber. Check the owner’s manual to compare this figure against the specified allowable range of camber.

References

• Ozebiz: Align
• Negative-Camber: Alignment