Sponsored by The Tire Rack

[Fraggy]

I am considering purchasing a CPO 09 335 sedan. The used car manager decided to put the sport line wheels from an F 30 on to that car using the original tires. The tire size is 225/45/18 versus the cars original 225/40/18.

I used the Tire Rack calculator and basically what it told me is that the new overall diameter would be nearly 1 inch larger. The calculator then went onto say that at 60 mph The speedometer would be reading 62 mph. I'm a bit confused by this, as my tiny brain leads me to believe that a larger overall tire, at 60 miles an hour would be turning more slowly than the smaller tire and showing a slower reading at 60 mph.

Please help me understand this, as I'm planning to look at the vehicle today and possibly purchase.

[Doctor///M]

not so sure about that swap... and yeah the sidewalls are thicker on the F30's. Is the F30 wheel setup a staggered one though? Make sure, cuz you don't wanna be running 225's in the back of the 09.

[Fraggy]

No, they're not staggered but that's okay for now I can live with it for a few months. I might even sell the wheels shortly too.

[bmw325i]

The calculator is right, think about it this way the larger diameter tire would cover more distance in one rotation than a smaller tire. I wouldn't worry about it though in fact your speedometer will be more accurate with the larger tires.

What I would worry about is traction with the 225's in the back I don't know whether or not that would be a problem

[Fraggy]

I'm gonna see how it all works out. I may sell them too as they fetch a pretty penny on the other board. But they look really nice on an E90 too.

And yes, my speedo should be almost correct now too