Originally Posted by JameB
I'd always go for manufacturer's figures but how fast you go round corners will make a bigger different to your tyre wear over the long term than a few PSI here or there.
If I recall correctly, BMW's recommended pressures for my old E46 were something ridiculous like 28psi front 32 rear. I'd suggest these have a lot more to do with turning the car into an understeering pig to avoid lawsuits from inexperienced American RWDers than with providing an enjoyable motoring experience.
Whatever, they certainly stuffed the steering feel and made it handle very much like my wife's 10 year old Saab 9000