Odin said:
I'm running 215x40x16 but I'm going to change back to 205's because I think the bigger tyres, Put to much strain on the transmission.
I feel its better to let the tyres loose some grip rather than break me gear casing, Also I think it handled better on the 205's personally.
215/40/16 comapred to 205/45/16 will put "marginally" less strain on your gearbox, will have "marginally" more sideways grip but "marginally" less braking/accelerating grip and for what its worth be "marginally" closer in diameter to OE.
BUT this all depends so much on your choice of tyre and even the same tyre in a different size can be produced differently so the rule book is really just a guide.
I was looking at a semi slick in a 205/45/16 vs a road tyre in a 215/40/16 but this boiled down to semi slick vs road tyre for what I do, the size is just noise.
Rob, having said all that, bigger profile tyres on your car might work better because you have such stiff springs your sidewalls become your only suspension.
IIRC, you used to run Toyo T1S, these have a soggy sidewall in any size but that might have been helping your ride. Even if you moved to T1R, they have a marginally stiffer sidewall. On my everyday car, the previous owner has some uber-sports Bridgestone S03's. They were hugely grippy but the said PO also ran them at around 28psi becasue they were uncomfortable on poor roads. Changing only the tyre to a more sports-touring orientated tyre, I can run a more motorway/response friendly 35psi.