Probably answered before but here goes...I want to put khumo auto x tires on my stock rims but have no idea about sizes...can some one please help??

It can't rub the wheel well...doubt it could anyway with 16" wheels but thought I would mention it

 

Well I have 245/45/16 Kumho's on my stock wheels, with 2 inch drop springs. They rubbed in the fromt slightly, but that was due to worn upper strut mounts. I changed the mounts and now she's fine

 

255/50R16 are the largest tires you can put on stock rims. You wouldn't want them on the car though cause they're too high profile for auto-x. 245/45R16 is almost the exact same diameter as the stock 225/50R16, so those are the best choice for stock rims.

 

go with 245/45/16 ..."Mazduh" should have put these on to begin with.....

 

As everyone said...245/45/ZR 16's. This is the best upgraded tire size for the stock rim. Will give you much more rear end cornering capabilities over stock size. This is also the prefered size used by autocrossers.