Good point, they do tend to crack and perish after 'X' amount of years if not driven regularly but should have been picked up by the person doing the MOT long before causing steering problems, as per the UK, here in Spain many things determine whether a cars tyre passes the ITV (MOT), age being used as a final decision maker if there is any speculation at to condition, small cracks for example, somewhere between small allowing a pass to possibly too large to not.
Obviously the 1.6 mm wear limit (1 mm on commercials), of course but also general condition, 'blocking' that is out of shape tread pattern normally showing after a tyre has been run flat damaging the internal structure and then being repaired, cracking between the treads, tyre wall damage no canvas to be showing in cuts and nicks and of course bulges, age is taken in consideration only if there are other issues although around eight years seems to be the turning point between a pass or a fail. Re cracks in the tread, this seems to be isolated to certain brands and also origin, for example China and Siberia seem to be worse, I used to replace more tyres from cracking due to the heat than for actually being worn out.
As an aside, tyres MUST match across the axle for example brand A and A on the front axle and B and B on the rear is fine, but A and B on the same axle is an automatic fail, so more often than not a damaged tyre say halfway through it's life will mean the purchase of two new ones.
Regards
Dave
