245s will fit perfectly OK on a 7.5" rim.
the OP was quoting 40 profiles for both sizes
yes they will fit, but everything I've read recommends a 8" rim for a 245 tyre,
Gaz, you need to look a little deeper at this - yes, 245
is recommended for an 8" rim width. However, it is also permissible to fit it on a rim as narrow as 7.5", or as wide as 9". So whilst 8" is the
ideal width, there is clearly a wider scope for narrower or wider rims for the 245.
it may give a comfier ride but would lose some sharpness to the handling
Huh, disagree with both. If you are going from a 225/40 to a 245/40, then all other things being equal (tyre make/type, load index, etc), then there would be no change in comfort. And there would be no loss in 'sharpness' to the handling either, in fact, wider tyres will improve handling stability during hard cornering.
and would affect the speedo readings too
Agreed - but rather than speculating, the maths need to be done. Don't fo rget that on the standard sized boots, the GTIs speedo over-reads (just like all cars). So, as an example, at 5,000 rpm in 4th gear (DSG), on the OEM 225/40 size, the speedo reads 90mph, but the genuine actual speed is 83 (speedo over-reads by 7mph) - but at the same revs and gear with 235/40 boots, the speedo reads 89mph, but now the genuine actual speed is 84 (speedo over-reads by 5mph). So, if anything, 245/40 will make the speedo even more accurate.
