Thanks for the input, everyone, very helpful. The OEM tire size is 275/55R20 (sorry for not including that in my original post), and I'm gathering that the general consensus is that a new wheel size is not necessary, so I'm looking at replacing the current tires with the Michelin-LTX M/S2. I guess my younger brother implied that our Sequoia's big rims were more for looks than towing, but he lives in Tahoe and does a lot of complicated rock crawling. He drives a Ford F350 van customized as a deep-off road rig, and it's all function! We're not planning on doing anything more backcountry than the occasional graded dirt road in summer in a national forest campground, and we're definitely keeping the GVWR below 5000. Thanks again, I'll let you all know what we go with for a TT!
