When you’re driving along in your car, all of the wheels are heading in the same direction as the car, aren’t they?
Well, no they are not!
General Tyre Safety Standard
The alignment of the wheels on the average car is specified such that (most of the time) the wheels and tyres are presented nice and squarely to the road. This alignment specification is designed to compensate for steering, braking and acceleration forces, suspension movement (as well as body-roll) during cornering, so that when any of the aforementioned actions take place, the wheel is still sitting squarely on the road. So when a wheel is out-of-alignment, the effect is that it will not be rolling “squarely” to the road. This means that some part of that tyre will be subjected to a higher contact pressure or “scrubbing” and will subsequently suffer increased wear rate.
Bridgestone’s advice to all motorists is to get your car wheel aligned very 10,000km (or yearly) to make sure you get the most out of your tyres.