guys you are quibbling over a 3% difference in rolling radius, get outside and enjoy the weather

Sussex put some more mileage on the car to wear the tyre tread down a bit ;)

Gotta love the debates LMAO

Good debate but aren't we missing the bigger picture - 17" alloys look so much better than the 15" ones??

Thanks for all your help (interspersed with debate on physics!!)

MPG definately about 5-7mpg lower than I got on my 15"s and acceleration is not quite as good. But will give it a bit of time. Its not just a case of the MPG reader being out as I am checking the miles to empty gauge and the fuel dial as well as well as the miles covered since I pressed the trip.

As for looks? The 17" titanium X alloys are gorgeous!

Lol thanks guys.. I'm pretty adament that the reduced acceleration will be due to the rolling radius, NOT any difference in tyre profiele or wideness though.

Lol thanks guys.. I'm pretty adament that the reduced acceleration will be due to the rolling radius, NOT any difference in tyre profiele or wideness though.

You should take into account that wider, larger alloys will be heavier (probably) so it would take more power to get them spinning in the first place, but this would probably only effect acceleration and not top speed

Also worth mentioning that a larger circumference will travel a greater distance with one turn of the axel

i.e. a greater top speed.

Do the 17" have a wider profile than the 15"?

Do the 17" have a different grip to the 15"?

Do the 17" weigh more than the 15"?

I know this all depends on the tyre not particularly the wheel itself, but would still be interesting to know how the standard provided tyres on both the 15" and 17" compare.