Tire size changes in HP Tuners

[vipermike2002]

I put on my winter tires a few days ago and would like the pcm to account for the size difference so my speedometer isnt off. My summer tires are 245 50 R16's my winter tires are 225 50 R16's. I previously (with DHP Powertuner) I just changed the pulses per mile, but it seems HP Tuners has some calculator, so I tried that. It asks for the tire height and gear. I plugged those values in and hit enter or whatever. Flashed the car and went out for a drive. The first thing I noticed is that the part throttle shifts are ALOT firmer (I like this) then I went WOT and the car proceeded to make a 6500+ RPM shift. This did not en tice me and probably not my stock valve springs either. My car used to shift at maybe 6200 at most, so this wasn't normal. I went and looked over the file I flashed onto the car after I used the HPT calculator to account for the tire size change. Seems settings in the speedometer section were changed, Part throttle shift speeds, wot shift speeds, and TCC settings were changed. I flashed back the settings that were loaded before and went for a drive. Everything was back to normal, but I still would like to know the correct way to account for a tire size change. If I use the HPT tire size calculator do I need to adjust the shift points again?
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[vipermike2002]

Yes I noticed the scale trans after I let it adjust. 2000 GTP. stock 2.93 gearing.

[Ivan]

This adjustment maybe different from car to car even on the same brand, but inyour Grand Prix its probably the same as my V6 Firebird, so..., in the unit conversion calc filll the tire size calc with the tire specs (ej. 225 50 16) ant it will give you the tire height. Divide the tire height by the diff gear (2.93) and write that number on the new speedometer space in the VCM editor, select auto scale if you want HPTuner to adjust the shift points and hit commit, save with a new name and flash.