Originally Posted by James T. Kirk
Apples and Oranges.
M3 curb weight:
Coupe: 3,704 lb (1,680 kg)
Sedan: 3,926 lb (1,781 kg)
Convertible: 4,145 lb (1,880 kg)
Cayman S curb weight:
2,954 lb (1,340 kg)
Yeah those numbers look odd. The sedan is only 40lbs heavier than the coupe. The vert is pretty close to what you have but I'm pretty sure the Coupe was somewhere around 3680 wet and the sedan 3720, but I'm too lazy to confirm.