When I reset my Smarty for the tire height (35"), does this make all things correct...meaning the mileage computer in the overhead, odometer, RPM's, and speedometer...so if my computer says I drove 400 miles did I actually drive 400 miles? The taller tires seem to lower the RPM's a nice bit at the higher speeds, just want to make sure everything is reading accurately. Thanks.

 

Yep...when you reset tire size with Smarty, it resets the overhead and odometer.

 

The mileage computer in the overhead will never be right. It will set the ABS correct for Odometer/Speedometer and Trip computer. But the overhead is going to be off, some worse than others. My overhead reads anywhere from 4-5 mpg high depending on the Smarty/TST/EZ settings. It was not right when the truck was stock and performance boxes/downloaders just make it worse.

 

And I have found the Smarty to be off slightly. When I installed 35 inch tires (new Toyo MTs), made the change with the Smarty to 35 inches, and then checked against a GPS, I was still off. Had to make fine tune adjustments, I think I am at 34.83 or something like that now... I don't think alot of people ever check there MPH against a GPS and make adjustments, which is one of the reason I take most mileage claims with a grain of salt...

 

Many manufacturers also round up on the tire height from actual measurements. You can usually find the actual tire height with the tire specs on their websites. I think rim width also affects tire height a little.

 

I have had to adjust actual ABS rev per mile even after the dealer set to available option with DRBIII. I have BFG 285/70/17s 32.1" is about as close to GPS as I can get. Manufacturer specs says 32.7". If you measure the actual rolling diameter after on the truck it is usually less than manufacturer specs.

 

Ya, I've found the same with the speedo. and had to adjust to match the GPS. Thanks for the info.