255/40-17 on stock rims?

Hi all,

In my never ending hunt for more grip on the track I went to 205/40-17 front and 245/35-18 rears. (worked just fine)

However, the Kumho V70As I used have been discontinued and there are few, if any tyres that both fir hte car AND get me safely to and from the track…

I bought a pair of 245/40-18 Trofeo Rs, but they are just too big for the Exige S2.

So my question is as follows:

Did anyone try to fit a 255/40-17 tyre to the stock rear rims?
If so, what tyre?