Diagnosing Problems From Tyre Wear

Firstly, let me state my views on rotating your tyres. This is the practice of swapping the front and back tyres to even out the wear. I personally don't think this is a particularly clever thing to do. Think about it: the tyres begin to wear in a pattern, however good or bad, that matches their position on the car. If you now change them all around, you end up with tyres worn for the rear being placed on the front and vice versa. The upside of it, of course, (which many people will tell you) is even overall tyre wear. By this, they mean wear in the tread depth. This is a valid point, but if you can't be bothered to buy a new pair of tyres when the old pair wear too much, then you shouldn't be on the road, let alone kidding yourself that putting worn front tyres on the back and partly worn back tyres on the front will cure your problem. But that's only my point of view.
Your tyre wear pattern can tell you a lot about any problems you might be having with the wheel/tyre/suspension geometry setup. The first two signs to look for are over- and under-inflation. These are relatively easy to spot:

Under-inflation	Correct	Over-inflation

Here's a generic fault-finding table for most types of tyre wear:

Problem	Cause
Shoulder Wear Both Shoulders wearing faster than the centre of the tread
	Under-inflation
	Repeated high-speed cornering
	Improper matching of rims and tyres
	Tyres haven't been rotated recently
Centre Wear The centre of the tread is wearing faster than the shoulders
	Over-inflation
	Improper matching of rims and tyres
	Tyres haven't been rotated recently
One-sided wear One side of the tyre wearing unusually fast
	Improper wheel alignment (especially camber)
	Tyres haven't been rotated recently
Spot wear A part (or a few parts) of the circumference of the tread are wearing faster than other parts.
	Faulty suspension, rotating parts or brake parts
	Dynamic imbalance of tyre/rim assembly
	Excessive runout of tyre and rim assembly
	Sudden braking and rapid starting
	Under inflation
Diagonal wear A part (or a few parts) of the tread are wearing diagonally faster than other parts.
	Faulty suspension, rotating parts or brake parts
	Improper wheel alignment
	Dynamic imbalance of tyre/rim assembly
	Tyres haven't been rotated recently
	Under inflation
Feather-edged wear The blocks or ribs of the tread are wearing in a feather-edge pattern
	Improper wheel alignment (faulty toe-in)
	Bent axle beam