How to do a String Line Wheel Alignment
This article will cover how to do a basic Formula Vee wheel alignment. This article refers to what is known as the string method which is the only practical method you can use at a racetrack.
Firstly, you need to get something that you can tie string to that has a height roughly at the axle height of the car. Two bars with pins the same distance apart set up on car stands will do. The idea here is to set two parallel strings either side of the car and have the car set up with its centreline parallel to the strings.
When you measure from the string to the car you won’t have the same measurement front to rear, but side to side will be. The measurement from both front axles to the string may be 100mm but both of the rear axles may be 90mm.
Providing that the string in front of and behind the car is the same distance apart, and both sides at the front axle are the same and both sides at the rear axle are the same, then the car should be parallel inside the “box”.
Depending on the type of rear suspension you have, you’ll need fairly flat ground, but not spirit level flat. For a twin coil over or rear torsion car, you will, but that’s not going to be covered here. Once you’ve got your car straight inside the “box”, you’ll need to set the steering wheel straight ahead and come up with a method to hold it there.
It must be noted that if you are going to adjust camber/caster, you have to do this first. Any time you change camber/caster (the eccentric nut under the top ball joint will do both) on a ball joint front end, toe will change. Measure out from the string to the front of the tyre, and then from the rear of the front tyre to the string. If those measurements are 95mm at the front and 100mm at the rear on the left-hand side, for example, then that side has 5mm toe out.
Repeat this measuring process for the remaining three corners and adjust according to the settings required. NOTE that measuring off the tyre, NOT the rim, will provide more accurate measurements. The rim’s straightness will depend on how many curbs it has hit, and some rims can be damaged enough to affect the measurement. These small deviations in the rim will affect your alignment. The tyre on the other hand will tend to even itself out due to tyre pressure.
This article provides a basic reference as to the method of checking toe in/toe out. What settings you adopt will depend on the manufacturer’s recommendations, however you can read the 2020 Dunlop Tyre article that will provide some additional insights.
Why not grab the spanners and have a go?