Thanks HP2 and Travis. HP2, both sizes are OEM - 295s come on corvettes, and the 335 on vipers.
So when does the weight become a problem? Anybody running 335 35 18 on the road course? I'm just looking to find out if the extra unsprung weight of this wheel/tire combo affects acceleration, braking, control, and lap times, or if the extra footprint counters all those aspects.