Had my speedometer recalibrated by a dealer yesterday and had the opportunity to watch the tech do it. All he did was go into his computer and select the new tire size.....is this all that they need to do? Took less than 5 minutes. Seems simple but I guess if it's all computer driven...

Info on the truck and tires:
2012 Eco Supercrew
Went from stock 265/60 R18 to 275/55 R20

 

Ya you gotta have thier special tool (computer) or a programmer but thats all there is too it (assuming you have stock gearing)

 

@M&D - That's all they did was hook their computer up to my truck and selected the new size. The tech did it for me at no cost which is nice but he said that they charge close to $100 for it. I guess with the right tools it can be a quick fix. Just seemed way to simple....

 

Ya its interesting how much these new vehicles, even trucks, are computer controlled.

 

I was at the dealer today, they told me that my computer was set to the largest tire size available and that there wasn't anything else they could do. I went from stock 275/55/20 to 275/65/20. Thankfully there was no charge.

 

I went from 275/55/20 to 275/65/20, they never said anything about not being able to do it. I checked the speed afterwards and at 70 mph it's 2 mph over. Anything 50 or under was 1 -2 over and 40 and less was pretty much exact. I can live with that. And my dealer did it for no money.

 

is the Raptor tire.....which is just over a 34" diameter tire....

Your 275/65-20s area about 34", too.

Some dealers seem to be able to program any available size, while others can only program sizes that came with the trim level of the particular truck.

I used a Hypertech Speedometer Calibrator to adjust from 275/55-20 to 275/65-20.

Northlight

 

Im gonna try another dealer and see what happens if not i guess im gonna buy a tuner