They’re black, they’re round, they cost you eighty pound

Although most tyres are made to very high quality standards, there are still variations in the thickness of the rubber, the steel belts and the radial webbing that form the structure. One consequence of the variations is a slight weight difference around the tyre. This is well known and easily cured by balancing the wheel and tyre.

A less well known effect of the variability is something called run-out – a measure of how straight the tyre will run if fitted to a wheel and allowed to roll along a flat level surface. Some will run straight and true, others will veer to the left or right in varying degrees. You will see an indication of this on most new tyres – have you ever noticed coloured lines running around the tread on your new tyre? Some of these are to give the tyre distributors easy to read information about where the tyre should be shipped to, but one of them will be a run-out indicator – usually red or blue, and the extreme left or right hand line. The nearer to the centre it is, the straighter the tyre will run, and which side of the centre it is denotes the direction of the run-out.

A steering problem can arise if both tyres on the front axle happen to run out significantly in the same direction. Ideally, when you’re next buying new tyres you should select two with run-out of about the same amount, but in opposite directions – in other words, with the coloured lines both to the inside of the centre of the tyre, or both to the outside. That way the two will cancel each other out and you’ll get straight steering.

Regardless of the tyre combination, a regular weekly check of the tyre pressure – when they are cold – is the best way to avoid premature wear. You will feel the improvement in the fuel consumption as well. And a quick check for condition (no cuts, bulges, or screws sticking out of the rubber!) at the same time is good practice, too.