MoPaR oR No CaR
I did a quick check at TireRack.com and found the calculation for tire diameter based on the tire size, no snooping required. :lol:Wow, your quick, I went and snoped around a couple of lots to get the same measurements.
Anyway, about the fuel, the online chat with the engineer the other week, this came up, now everything regarding this revolved around the SRT platform, but he said that the auto with (??) gears, vs. the 6 spd with 3.92's, the stick should get the same to 1 maybe 2 mpg better, that's if you can believe the engineers , in the RT with the 5.7 and all of the changes they made to that engine for this year, it'll probably be more of a difference. If you really look at the gear break downs in the sticks, the first 4 gears are set up for performance, 5 and 6 are definetly getting into the overdrive category, which is pretty much how he described it. Image that.
I don't think the wheel/tire combo's will matter hardly at all unless you change the tire package to something off what they have figured, i.e. 26" or 29" diameters, something like that.
I had been under the impression that the different rear gears were to compensate for overall diameter differences, but that doesn't appear to be the case here, although a 1/2 inch may make a bigger difference than I know. Rather, the desired gear for maximum performance is the 3.92 and to prevent potential shredding of the rear tires during fast starts they need to install 20" wheels with Z rated rubber. By keeping the 3.73 rear for the 18" wheels, they're safe with lower rated, taller rubber and slightly slower starts. I'm guessing that the 6 speed R/T with the 3.73 rear will get a little better mileage than the 3.92 too.
This is all speculation mind you, and someone here with more experience than me is welcome to throw the BS flag.