Changing Tire Size, Slightly...do I Need To Re-program?

[chrisa]

'08 NBS Sierra, going from factory 245/70r17 to (new wheels) 265/65r18. the new size is like an inch taller. should i reprogram for speedo, or trans shift points?

[Knowklew]

yes

[03z71]

You certainly don't have to (it looks like your speedo will be 3.5% off which isn't too much, but this would be a perfect excuse for a custom tune. Bottom line, if you're thinking about getting a tune, do it, if you have no intention to get one, you should be fine without...