Tyre age and grip

Tyres lose grip as they age, regardless of use and tread depth. We do see many classic Jaguars come to us with 15 or 20 year-old tyres, or sometimes with the original 1980’s tyres. While they may still pass the MoT on tread depth, they will certainly have reduced grip. I have experienced this many times when conducting road tests, and I find the car losing back-end grip when I wouldn’t expect it. This is of course very dangerous, since one needs maximum grip in an emergency, yet one would not notice the issue when driving leisurely.

Tyre manufacturers have a vested interest in selling tyres as frequently as possible, but nevertheless their recommendations make sense. A decent article here: https://www.uniroyal-tyres.com/car/service-knowledge/the-importance-of-tyre-age-as-well-as-tread-depth/

The age of the tyre can be easily found by looking for the age code on the sidewall (sometimes on the inside). This is 4 digits, preceded by the letters “DoT” and some miscellaneous numbers/letters. The first 2 letters are the week (1-52) and the last 2 the year of manufacture, e.g. DoT 3608 is week 36 of 2008. Even earlier tyres have a 3 digit code, sometimes with a right-facing triangle before them, indicating the tyre are either 1980 year or 1990 year respectively – in both cases too old to use….