[JoeyBimX5din]

Originally Posted by jandref321

I hadn't considered the tire's circumference affect on the mpg gauge. The original person on Xoupost who used these size tires said that the speedo was exactly accurate with the larger tires since they manufacture a 2mph addition. I don't know how he tested it, maybe those speed trap things at the side of the road that tell you how fast you're going. But, that would partially explain why all the BMWs I've owned have had better gas mileage than advertised.

The actual speed difference always changes with speed though so you can't say its' accurate all the time anyway. I took my E46 M3 up to 175mph on the dash but gps was reading 162mph

The speed GPS aps they have for phones seem to work well. I believe there may be a built in amount of error in the factory calibration, in the above mentioned lift, my speedo was only a little fast by maybe a few percentage points.