all i know is that basically if you go from the clio's basic alloys, 15" wheels, to say the 16" your speedo does not need re calibrated as the difference in rolling radia is negegable dy to the reduced profile onthe 16's tyre, all it dows is make the wheel 10mm wider and a bit stiffer
, however if you stick onsay 17s, no mater what profile tyre you put on it has a detromental effect to your speed, as it increases the rolling radius by a couple % so when your speedo reads 70 you are going about 76-77. same if you put 14's on it woudl read about 65-67mph. also if you done calibrate your speedo, it iwll affect your trip computer and the cars over all mileage, i mean just a couple % increase in rolling radius can add 100's of miles on the clock a year, and will affect your mpg, and miles till you need to refule reading etc.
I like the idea of putting the 16's on the car the should fit no probs and will give the car the theres somehting diferrent but i dont know what it is look, but they are really hard to source and from what ive seen more expensive than the aftermarket 16's.