How exactly do u know how much air is to go in your tyre??

ok. you will find a white sticker either in door shut either side or in the glove box. failing that in your hand book, failing that tell me what model you have and i should be able to tell you.

no man.if only it were that easy..these arent the stock tyres....they are 205-45/16

my stock tyres are 15's tho..dont remember exact specs

I drive an mr2 with 205/50/16 and 225/50/16's can vary quiet a lot depend on how you like your car to drive but I find 32 front 35 rear suits me just fine....

ok thx.....

is there some theory behind determinig tyre presssure??

am sure there is but I've gone through asking around then seeing what the car feels like...