Just round the corner from me a bloke has bought a Kia Soul. Slightly smaller than my cmax but its got the biggest set of wheels I've seen [img]smileys/smiley3.gif[/img] on a smallish car - 18", apparently.
Quite apart from ride issues with wheels this big, it got me thinking [not something I do often] about the effect of wheel size on rpm and therefore mpg. My intuition tells me that the bigger the wheel circumference, or diameter, the less revolutions the engine needs to do at a given speed to cover a given distance. There seems therefore a point in having big wheels insofar as the engine needs to work less hard and therefore will use less fuel. Is my reasoning correct, or am I thinking nonsense, as usual?
My second point is, of course, what are the sizes of wheel that will fit a cmax, and, if I had bigger wheels fitted, would I then have to recalibrate everything [speedo, rev counter, computers, etc] which would make the whole mod impossible? Finally, is there anyone out there with a 1.6 petrol [100hp] zetec with 16"ers for comparison? My car has 15"ers and I get 3250 revs at 70mph with one on board on the flat.
Many thanks as always.