Hello everyone,
I just had a quick question I needed to ask. Earlier this year I decided to get new wheels and tires for my car. The wheels I had on my car at the current time (the ones I bought the car with) were Alba Lexo 540's. They actually looked very nice on the car. The only problem I encountered was that there was a crack in one of the wheels, causing me to loose half of my tire pressure within a matter of a week.

My old tire specs are 235/45z/R17.
My new tire specs are 245/30z/R20.

Obviously the circumference of the tire is larger than stock.

I have researched up the ying yang about speedometer recalibrations. I know that if I had had the Navigation system in my car I might have been able to adjust something along the lines of tire size. Since I do have a base, I don't have that luxury.

There HAS to be a way to compensate for the larger wheels whether it be a tuner, a honda OBD2 tool, or a program and cord that I can connect my laptop up to the cars computer port.

My gas mileage has been severely affected. I used to be able to get 18 mpg in the city if I really tried. Now it is more like 14 mpg.

I don't want to go back to stock sized wheels and tires. I finally found wheels that I like.

I need some input. This is driving me crazy.

 

mighty car mod from Australia had a DIY on this although it will require some work to yank the cluster out and tap into the wiring and adjust the speed as you travel accordingly by using a portable GPS or smart phone app.

 

You could use a 235/30/20 tire to help reduce the speedo error from 1.8% to 0.9%. If you can, I would fit on 225/30/20 and make the speedo dead accurate to stock size, 0% error.
The larger diameter tire is actually making your speedo run fast so your MPG calculation is actually on the conservative side. Sorry to break the bad news. But you gotta pay to play. Running 20s are a lot heavier then your stock tires or even 18s.