Not often will wheel alignment be on the minds of the average motorist. It does not form part of any particular service regimen or MOT test. Some will be reactive to problems resulting from poor alignment such as when steering or handling are adversely affected, or when uneven tyre wear becomes apparent after a few thousand miles of driving. Others will be slightly more proactive with regard to the alignment process – for example they may have it checked after a tyre replacement for peace of mind against their new purchase. A vehicle with an alignment that falls within the specifications of the manufacturer will not only enhance the roadholding capability but improve fuel consumption, so its role should not be underestimated. With the abundance of so-called ‘fourwheel alignment’ services typically seen in many fast-fit centres across the country I investigated whether such an alignment process can be performed by a DIYer and if any potential savings can be made in the process. As you will see over the next few pages, I ran an alignment on my 2006 BMW 130i in my home garage using the string method without the need for any expensive equipment.
What is wheel alignment?
While there are many components that make up a vehicle’s suspension system, they all perform a specific function to ensure the road wheels are in the best orientation. Not only does a wheel turn left and right, which the suspension must accommodate for, it also tilts inwards and outwards as the chassis moves up and down. Each of these movements can be tweaked in relation to each other to ensure maximum contact with the road surface is accomplished improving handling, fuel economy and avoiding uneven braking. As components wear, such as track control bushes, or even when the suspension system is subjected to harsh forces (eg. driving over potholes) the ideal angles that the manufacturer sets at the factory begin to deviate away from the ideal. The alignment process attempts to correct any deviations back again, although it is not a substitution for poor quality or worn-out suspension; the alignment should be made once these parts have been replaced.
The adjustment of various suspension and steering components is performed through changing three main alignment angles – toe, camber and caster. The first two of these affect tyre wear and handling the most. Assuming that the steering wheel is fixed dead-straight, adjusting toe will control how much the wheels point forward independently. If viewing the wheels from above, ‘toe in’ (a positive number measured in degrees) will have the wheels pointing slightly towards the middle of the vehicle, while ‘toe out’ (a negative number) will have them pointing slightly outwards. A vehicle set with zero or neutral toe means the wheels are perfectly straight ahead. The camber angle is where either the upper part of the wheel is closer to t
