Read it again:

 

If it's not intuitive to you, then either (a) do the calculations of speedometer conversion and shift mph conversion so you can see that the net effect is nil or (b) simply put the tires on and see for yourself that it shifts at the same place.

Wow. I just looked at your profile - you are a computer programmer and you can't see this?

 

I see what your saying, but it only works if you originally tune for the smaller tire then switch to the larger, but if for some reason it is tuned for the larger tire and the smaller is put on it won't work...

Hence why you said not changing the tune... The reason I wasn't thinking about that is because I will be doing the rear and tires at the same time and was going to have to retune anyway and was thinking about tuning for the bigger tire from the start and that is why the issue stuck in my head...

 

Yeah if you programmed it for the track tires then your speedo would be off on the street.

I'd just program it for the street tires.

 

Why would you need to worry about any of this? Program the mph lower than when you'd want to shift to occur, that way the pcm uses the rpm to know when to shift.
You really don't want to trust your VSS after a nice hard launch on an A4, do you?

 

I know this is an old thread, but would this work? Have the computer programmed to shift at a lower speed than needed, and have it shift on RPM instead of speed? I'm confused how something like this would work.