Hey guys, I'm about to hit the track with actual slicks FINALLY, lol. As I understand it I'm going from a 275/45/20 which is 29.7ish tall. I got some 28" Hoosiers for it. When I change the diameter in HPTuners will it bounce off the rev limiter before shifting or even shift at all? What do you do to prevent that? I'm pretty f n lost when it comes to hp! I'm running a 215/75-16 up front also.

 

You can change it in HPT and it will automatically change the shift points. But you really don't know if it will be perfect or not. You will have to fine tune the shift mph when you get to the track. I always make the shift mph four or five mph less than where it should shift. That way it will shift right at the WOT rpm you set. Hope that helps

 

just subtract about 5 mph from your 1-2 and 2-3 WOT upshift. if that dont work,, subtracto another 5mph..

 

The trans is going to shift based on wot rpm as long as the wot shift mph is met (or vice-versa in your case). Set the wot mph shift point according to a 28" tire and leave the tire size as your street tire. Mine is set up this way and I don't change the tune when I go to the track swapping out my 29" street tires with a 28" slick and it shifts at set rpm both on the street and track.

 

Okay thanks fellas... The 27" front won't affect anything correct? Mph is based off of the rear wheels right?

 

Yes, front tires don't matter