Stock, the STi comes with 17x8 rims shod with 225/45/17 Bridgestone Potenza RE070. Not a bad setup, but there's room for improvement.

I've searched the forums for a definitive answer, but none has yet been found. What's the optimal plus size tire for the STi?

Keeping in mind that 225/45/17 is stock, the closest thing I can find is 255/40/17, but that will require an 8.5-inch rim, right? And it probably will cause a lot of rubbing under the fenders.

235/45/17 is an option, and it will likely cause no rubbing, but that runs the speedometer too slowly and messes with gearing by 1.4% meaning 60mph on stock tires equals 59.1mph. Not too bad, but not the best setup, either.

Now 245/45 could work, but I'm not sure if a) it will rub or b) if 2.77% speedometer error will mess with the car too much. The problem is, Toyo doesn't make the RA-1 in that size, and Michelin doesn't make the PS2 in that size.

Going a little slimmer, 245/40 will run the speedometer 1% too fast making 60mph 60.6 mph. But Michelin does make the PS2s in that size. Its just generally not a popular tire size.

Obviously, the best solution would be to get 255/35/18s and 9" wide wheels but that would require a chargespeed kit and spacers. :P


Thanks in advance.

 

You are making you life too hard. The 245/40s should fit w/o rubbing on the on OE 8 in wheels, or if you insist 255/40s would probably work on those wheels, although 8.5 or 9in wheels would be better. 245/45s would be way too tall -about 6 or 7/10s of an inch too tall.