TREAD DEPTH
It is important to check your tyres every week, check the depth of the tread, tyres should be replaced at 2mm minimum.
The law states you must have 1.6mm across the central 3/4 of the tread with visible tread on the remainder, remember if stopped by the Police it is 3 points for each illegal tyre plus a hefty fine.
Check to ensure that the sidewall of the tyre does not have any cuts or bulges.
If your tyre is old the rubber deteriorates and you can have cracking appear on the side wall of in the tread itself, at this point the tyre will need to be replaced.