'90 Runner, 2wd, auto. Just ID'd my rear (so to speak) and got a G252 axle code. As I understand it, that's the 4.56 gearing. Stock tire size is 225/75/15 with a 31/10.5/15 option. Will I be overgeared (?) if I go with the 225's???? I'd rather go with the 31's for a bit more clearance and appearance, but don't want to sacrifice mpg's as it'll be my commuter.

I know the 4.56 is correct for 31's on a manual tranny, but what about auto's??? Can I go with 31's without robbing mpgs?
Qdude <img src="/forums/images/graemlins/notooth.gif" alt="" /> <img src="/forums/images/graemlins/notooth.gif" alt="" />

Auto's w/31's had 4.87 oem gears, so you wont be over geared w/the the 225's. However your mpg will suffer w/31's. My sister got only 13 combined w/her '95 3.0 runner w/31's and 4.56 gears. Since you only have a 2wd and want to run 31's, it will only cost you about $2-300 to get a used 4.87 rear oem diff.

How bad your mpg loss will be w/31's depends on what it s now. Than figure what 11% less will cost you, since 31's are 10.71% taller than the 225's, you will basically go only 89 miles on the same amount of gas that you used to go 100 miles.

Depending on your current mpg and how far you commute, the extra $300 for the 4.87 diff may not be that much w/the current cost of gas.

You could always go with an LT235/75R15 or a 30x9.50.15 they are both about the same size just one is metric sizing and one is standard. The 235's will also be in stock at any tire store. Then you would be right in between the two sizes I think 225 are way too small looking and then your mileage wouldn't really suffer too much if you even notice.

Brian