Check Wheel Alignment Periodically
In a perfect world with perfect road conditions, you probably would not need to give much attention to your tyres and wheels. The rubber would wear out evenly and the balance would remain perfect. Of course, due to manufacturing variations, every tyre and wheel has a slight imbalance which is why a counterweight has to be added on the wheel to bring about proper balance.
Balancing wheels is recommended every six month, more frequently if you drive on rough roads. If you don’t have them balanced regularly, the tyres will wear out unevenly and cause uncomfortable vibrations. Unbalanced wheels/tyres also make the shock absorbers work more than necessary, accelerating their wear and tear.
The process of wheel balancing is quite straightforward and these days, there is computerised equipment to do it precisely. Generally, balancing can be done off the car but in some unusual conditions, there may be a need to do on-car balancing. In this case, a special machine which spins the wheel to a high speed is used to observe the imbalance.
While many motorists are aware of the need to do balancing periodically, not as many are aware of the need to also do wheel alignment, which is just as important. Like balancing, alignment should be done frequently if a lot of driving is done on rough ground – those who spend weekends driving off-road should take note! All the bumping around and dropping in and out of potholes gradually alters the alignment of the wheels. This will lead to irregular wear on the tyres as well as a deterioration in handling and grip. A very common indication of bad alignment is when the car pulls one side even when you are driving along a straight road.
Periodic alignment is also important as the tyres wear out and the suspension geometry will alter minutely. Also, whenever you put on a new set of tyres, it is a good idea to have the alignment checked. Again, the change in geometry may be invisible to the eye but if you care about your car, then you want everything to be precisely within specification.
Visual inspections can indicate if the alignment is off. Typically, if part of the tyre is wearing out faster, then the alignment is already out of spec. In fact, if such irregular wear is visible, the alignment has already been off for some time. However, not all irregular wear on tyres is due to alignment problems as incorrect inflation can also cause wear in the middle or on the sides. Generally, motorists who do not check tyre pressures regularly will find the outer sections of the treads wearing out quickly.
Unlike balancing, wheel alignment is a lengthier job and most shops have specialised computerised equipment. The precision to which adjustments have to be made are very fine – right down to degrees and millimetres. Each vehicle has different alignment specifications and this data is important for the job to be done properly. The data is usually in the alignment equipment so it is a matter of selecting the right model. Sometimes, data for rare cars (especially those reconditioned ones) is not available, in which case the mechanic will just ensure that the alignment is set in a general manner so that the tyres are not being ‘dragged’ along the road sideways.
The three elements involved in wheel alignment are angles referred to as caster, camber and toe. Caster is the angle between a vertical line and a line drawn through the centre of the ball joints (steering axis) when the vehicle is viewed from the side. The caster is considered ‘positive’ when the steering axis tilts toward the rear of the vehicle at the upper steering pivot.
Positive caster helps in maintaining directional control of a vehicle, ‘forcing’ the vehicle’s wheels to return a straight ahead position when cornering. You can feel this effect if you don’t hold the steering wheel tight as you drive around a corner. The geometry of most cars’ suspensions are set for positive caster but just how much depends on the philosophy of the chassis engineers as well as the type of car. If the caster is incorrect, there will be steering difficulty, increased road shocks and poorer straightline stability.
Camber is the angle between a perpendicular line and a line drawn through the centreline of the tyre when viewing from the front of the vehicle. When the camber is ‘positive’, the top of the left tyre tilts away from that of the right tyre. However, the amount of tilt is actually slight and may not always be visible to the eye. amber helps to distribute the vehicle’s weight across the tyre contact patch during cornering for reduced tread wear. It varies from vehicle to vehicle and although there are manufacturer’s specifications, some degree of variation is possible to achieve certain characteristics.
If the camber is not periodically checked and adjusted, there will be uneven tyre wear, poor steering response and it is likely that stability will be poor and the vehicle may wander.
Not all cars have adjustable camber, though. In some cars, the suspension units are designed with a fixed camber setting for cost reasons. This therefore makes assembly precision critical but generally, it is not a problem. Should a very bad bump or accident push the camber way off, the better tyre shops will have solutions to offer for adjusting the camber.
Toe refers to the angle between a line through the centre of a vehicle and lines drawn through the centrelines of the tyres when looking down from the top of the vehicle. Normally, in discussions on suspension geometry, terms such as ‘toe-in’ and ‘toe-out’ and these refer to the angle of the wheels. When they are closer together at the front than at the rear, the condition is called toe-in. When the wheels are closer together at the rear tan at the front, the condition is toe-out.
The toe adjustment is the most critical to tyre wear. Incorrect toe results in rapid and uneven wear. However, varying the toe can also bring about handling characteristics that may are different and perhaps better for certain types of drivers. For example, YS Khong, a former Malaysian rally champion, has his own philosophy in adjusting toe and usually suggests something different from what is recommended by the manufacturer. He says that it gives a better driving feel and nicer characteristics for sporty driving.
