Over on the US side of FChat, the recommended size for 355 rear tyres is 275/40/18 (OEM is 265/40/18). They reckon you only need to up the tyre pressures by a Psi to restore the handling balance. Seems like a good idea if a. you can get a better range of tyres in that size and b. the extra rear rubber adds a bit more grip. DOes anyone have any experience of fitting the larger rubber???