Piorun, that is one of the tire calculator sites that I use often and the one I used to run the calculation in my post. There's another site that I also use that gives a little better comparison but for the particular setup I'm looking at the math for speed seemed to go in a different direction. So maybe their formula is a little different. They also run a calculation to remain within 3% of original size so as to not put any stress on the brakes if you don't upgrade them. Here is the site:
http://www.1010tires.com/tiresizecalculator.asp
This site also seems to give the rim width range the tire can be put on and it looks like the tire I want to use will work but my concern is whether given the wide will the tire clear things in the wheel well. I'm guessing it will in the rear but in the front when you turn the maximum in either direction is what I'm worried about.
PT145