I currently run 265/75/16s on my '02 Rodeo Sport, but I will be going up in size (again) to 285/75/16s this Spring. How can I get the speedometer calibrated properly to the new tire size(s), and how can I set the new shift points w/ larger tires for the automatic transmission?

Even with 265s, the shift points are off. I am using a K&N air filter and Flowmaster muffler, but those two combined should not make that much of a difference compared to the larger tires. The local tire shops say that I need to go to Isuzu to set it all up, but the Isuzu Service Dept. tells me I'm out of luck... Any help would be great!

A.M.