I would like to upgrade to 18 in wheels on a 07 GMC Canyon (Colorado). Dealer specs tires that are 2 sizes too small. They say GM tested this size and it is the only one covered by warranty. They also say that the BIC would have to be reprogammed with a different tire size. Tire Rack and a tire dealer friend says stay with the correct 18 in size which the circumference matches the 15 in tire I have now. Will the MIL set when the speedometer is off by 2.1MPH? I could live with the speedometer not being exact but I don't want to have the BCI reset every spring and fall when I switch wheels and tires back and forth. I am using the 15s for snow. I hope a GM tech can answer this. Thanks.