ohnoesaz

Not to mention erroneous readings on the overall odometer. Youre basically commiting odometer fraud one way or another.

Recalibrate it. Now.

Also, the heavier 20" rims, which could be what, 8lbs heavier each corner of unsprung weight, times 4 corners, times 6 to convert to sprung weight, you're basically carrying 190-200lbs extra on the car after the conversion.

At least they look cool......... they do look cool, right?

airborneallthway

Maybe it's lead foot syndrome?

moosestang

Your odometer would also be affected, so your calculations would be off to.

My speedometer is off by 2-3mph at 70, but at 50 or below it seems right on.

loots06

I did not change my revs with the Tuner, I'll have to do that when I get home as I drove my car to work today.

157dB

How are you computing this MPG reading?
The OE trip computer or good ol math?
Whats the revs per mile of the tires removed
and the tires installed? Did you factor the difference
between the two.

Legion5

Mpg is calculated with the front wheels and not the back wheels, if you entered your rear wheel measurement then it will cause the errors

Kara

WOW be sure and update us!

Tracedaddy

Did you inflate the tires???

I suspect it's one of the issues mentioned above but just a "horse-sense" question...Are you going to the gas station twice as often?

zkiller

That seems odd because the rear wheels are connected to the driveshaft, which is connected to the transmission which I believe has your speed sensors.Since the drivetrain all runs off the back wheels where how do the front wheels come in to play?
Thereforewhen you change the revs per mile you would base it on the rear tire size.

Haze28

Thats what I was thinking too. I have different size tires out back and have everything set to the rear tire size. I can't see why MPG would be measured by the fronts....