I'm considering pushing 37s off until 2017 or at least until after next summer. My 35s have so much life left in them and there are other things I can spend my money on. My truck has already proven I don't NEED them.
I think this would be a great choice. The 37s will be a much bigger upgrade in Washington than in Moab. Ground clearance isn't the biggest issue on the vast majority of trails. Maximize your value in the tires you have...
What kind of RPM were your turning on the highway going to California? The the tire diameter should be under 7% different so at 3,000 it should only be a couple hundred RPM difference. Is that enough to get you out of the powerband or really impact your fuel economy? I know some engines are more picky that others.
I'm not sure my nearly stock gearing is really the best combo with my midrange cam...it doesn't seem to pull at higher RPM like my 85 did.
