Playing a race weekend (full practice 60mins, full qualifying, long race lengths) I have noticed the tyre life in practice is alot less than in qualifying and race. Practice on hards gives you approx 15 laps of life, but in qualifying and race you get 30-40 approx of life (screenshots supplied).
I noticed this on Miami with Williams (continuing a two player career after a two week break). I have tested it with different teams and tracks and the same behaviour is displayed.
I suspect this to be a bug since the last v1.03 update, as I didn't experience this issue previously.
