by Astraist » Wed Oct 03, 2012 11:21 pm
My view on the subject of tyres, as well as dampers, is that they are significant in more than one way, and the other way is poorly under rated. As of today, professionals in the fields of tyres (engineers, tyre fitters, tyre companies, the said article, etc...) are giving too much of a stress to the "secondary" or "passive" safety features of the tyre. i.e. it's ability to withstand pressure and not blow-out. For this end, even a bone-dry five year old tire with two millimeters of tread depth and 80,000 miles - will do.
However! I always address the subject of tyres from a primary or "active" safety perspective. A tyre needs to be more than just a piece of rubber that doesn't tear to bits as you drive. It should give you sufficient grip for cornering and mainly for braking in the event that a sudden stop is due.
True, this standard is not as easy to measure as a tyre's ressistance to rupture, but there usually is some limit you can true as to when the grip level of the tyre drops so dramatically that the stopping distances become all too long. I doubt that this factor has even been considered when collisions involving tyres are counted. If it was - the number of collisions that happened with the contribution of bad tyres would have increased dramatically.
I've found that tyres normaly age so much within merely three years, that they usually become unworthy of use even even if they have very few miles on them. In better weather conditions they can last longer, but I cannot imagine a tyre's compound remaining reasonably grippy after four years total.
The point is not to replace it when it breaks, or just before that, but replace it as a form of maintainence. The same applies for dampers. Sadly, leastways in my country, they only get replaced once they fail by squirting oil or getting stuck. However, even a damper with no hint of leakage becomes very "sloppy", so to speak, within 40-50 thousand miles and seriously reduces grip.