Hi Stephen, I would certainly recommend replacing these tyres. At this age, they are likely to have become very hard and quite possibly likely to fail if operating under arduous conditions – high speed/high temperature. I would also imagine that their performance in the rain would be rather suspect. I think there is a general tyre industry code suggesting that tyres should be replaced at around 10 years old regardless of visual condition due to the ageing degradation of the rubber.

Unless you desperately want to keep the original spec Pirelli P4000 tyres (there are very few tyres available in this size now – maybe only from Pirelli?), there are many other modern tyres available in a slightly different size. I’ve fitted Bridgestone Turanza 215/65R15 on my car (with the original wheels) – the outside diameter of this tyre is slightly smaller than the original Pirelli’s, so the car is now slightly lower geared and the speedo reads about 4-5mph faster than the true speed, and so you will be revving a little higher for the same speed than with the Pirelli’s (only a couple of hundred rpm difference). I think that this is a minor inconvenience for the benefit of having a more modern high performance tyre.

Personally, I think also that these modern  tyres with a slightly lower profile look better on the XJS that the P4000’s – I reckon that these tyres look just too big for the car.

Hope this helps, all the best. Norman.