Very weird. I got new tires which are 1.5" taller so my 3.42s are now effectively 3.31s A normal tank for me is 12.8 mpg. That's with just normal driving up to 2500 or so, and not 1 single WOT. This last tank I've been driving around a lot in 2nd gear and doing a lot of WOT. I expected my mileage to go way down. Instead it went up to 13.4 Only other change was a ported TB. Maybe this will make me reconsider 4.10s. Off the line acceleration is def. worse with the taller tires though, top of 2nd though is crazy.

 

Cool, but did you recalibrate your computer for the taller tire?

 

Dammit....I just got owned LOL. Forgot that my odo is now off

I know that my speedo reads a couple MPH higher than actual now. I guess this would mean my odo is now counting more distance than I'm actually traveling.

 

No, actually your speedo slows down with bigger tires so if anything you would have "theoretically" lost mileage. When you figure in the speedo error, on all my vehicles I've always picked up mileage. I don't doubt you for 1 minute.

 

Sorry I misspoke, you're correct. My speedo is reading slower than the speed I am actually going. It's weird on the highway, it will read 70 but I know I'm going closer to 75 than 70.

 

Use this wonderful calc: http://www.miata.net/garage/tirecalc.html

 

Oh and don't forget the bigger tires now will throw your tune off. Shift points of speed vs throttle position.

 

doesn't seem to be bothering the tune too much. I'm in no hurry to change it.

 

Not to over step hirdlej on the tire calc. But http://www.dakota-truck.net/TIRECALC/tirecalc.html is really good for the gears ratios and mileage. And http://www.bigcustomwheels.com/rt_specs.jsp is really great when comparing tire and rim sizes with adjustable offsets.