Great idea, but doesn't the increased diameter (and therefore circumference) corrupt the speedo reading ?
Going from 60 to 65 profile makes a difference in circumference of just over 3%. So speedo at 30mph will only change by about 1mph and at 70 mph, by just over 2mph. So not a worry at all, as speedos are usually high reading anyway.
It's the way I am going to go when I change my tyres next year.
