I have recently gone to a tire that is taller than stock and could swear that there is a difference in the way the car is shifting and when. Could the tire height difference actually have anything to do with this? I figure since shifts are computer controlled and based somewhat on speed data this is possible. Answers either way will be appreciated

 

bump.....

 

Taller tires will make it upshift later. Speedo will be off too.

If you get techincal about it you can look at your tach and speedo and see that shifts will still happen at the same rpm and mph. Problem is the the mph is off, you're actually going faster than it's reading.

 

yep he is right if you have a tuner have uhm retune for the new tire size. I think some hand helds can also adjust for tire sizes.

 

Yep, computer looks at vehicle speed and rpm when determining shifting. Both must meet a given parameter when shifting at WOT (ie, you must be above x rpm and above x mph before shift is commanded). Different tire diameter changes that. Nothing a tune can't fix.