It started brief... then I walked away from the computer... then I came back and added a bit, then had to run again... then when I got back I just said WTF and finished was I was thinking I was going to say
.
Regarding rolling resistance, Jimbo, it's actually more of a function of a few things:
1) how much you load your tire vs. what the load rating of the tire is,
2) the nature of the construction and tread compound (the stickier or more performance, the more rolling resistance), and
3) the operating tire pressure. Tire size is a factor, but it turns out to be a minor influence (not insignificant, just minor when compared to the other three).
Which brings me to a really rough segue... tire pressure. Once you've established a tire size, you have a lot of leeway with pressure - generally you want to optimize the tire footprint by selecting the appropriate tire pressure for the size tire you've picked
when operating at your load. So, even if you end up picking a really oversized tire, you can improve your grip by lowering the tire pressure (because it's likely if you have a car that would normally use a 90 load rating and you chose a 98 load rating tire, at normal tire pressures your tire would likely be overinflated).
Ran into this when autocrossing - in a Calais, it was necessary to drop the rear tire pressures down to about 18 psi when running competition - because the weight distribution was about 64% front, the rear tires at normal pressures had too much for the load placed on them (about half what was on the front tires).
I hope this is helping...
