# Mileage problems **URL:** \ **Category:** SON240sx Automotive\ **Created:** [May 3, 2009, 8:44pm UTC](https://forums.speedlife.net/t/mileage-problems/124138 "2009-05-03T20:44:06Z")\ **Posts on this page:** 1\ **Showing post:** 16
**Author:** ![AhmadG](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/ahmadg/32/5577_2.png) [@AhmadG](https://forums.speedlife.net/u/AhmadG)\ **Post date:** [May 6, 2009, 12:49am UTC](https://forums.speedlife.net/t/mileage-problems/124138/16 "2009-05-06T00:49:28Z")
> [@which wine to get?](https://forums.speedlife.net/t/which-wine-to-get/21822/49): > > no one ever seems to think about your tire sizes and gear ratio’s > > gawd! I multiply my odometer and speedometer readings by 1.031 to compensate for the increase in tire circumference going from 195/60/R15 to 225/45/R17. Go here to calculate the difference, its so useful, and quick. [http://www.miata.net/garage/tirecalc.html](http://www.miata.net/garage/tirecalc.html) I did a 5 spd. swap, but the final drive ratio should be identical to a manual car. 5th is a bit shorter than O/D on the auto, I’m doing 3350rpms at 120km/h. Seems a bit too high to me, that’s halfway to redline, cruising on the highway… I wanna scan my ECU, I have to save up some money to pay off debts and then buy that consult cable and software. Debts are obviously car related lol. --- _[View the full topic](https://forums.speedlife.net/t/mileage-problems/124138)._