What tyres should I buy ?

[Mark_B]

I just thought about the nitrogen thing for a minute, then realised... isn't compressed air composed of 4/5 th's nitrogen?, so after filling with air, up to 20% of it (not being nitrogen) leaks out, compared with pure nitrogen. Then, the leaked gas is replaced by more air, of which more than 80% again stays put. Then after that, only up to 4% is lost this time. Then the next top up, only 0.8% at most is lost.

Hey- how about filling tyres with helium? - it might make the car a lot lighter!

[poprivet]

I thought they used Nitrogen as it is completely free of water vapor, which is the main cause of pressure to temperature variations.

Helium would leak out very quickly due to the molecular size. In my motorcycle tyres I use Ultraseal and good old air to prevent leaks, and to run the tyres cooler. Would be expensive for 4 Jag tyres though.
Pop