Originally Posted by Jpjr
what could be more important than a meaty tire with a sidewall for trail running? it's really that simple. loaded overlands used to come with 18"s standard and now they offer 20"s because the wheel well opening got so much bigger.
The wheel well opening has nothing to do with it. The total diameter (wheel + tire) is the same whether you have 18" or 20" rims. The difference is that the tire on the 20" wheel has a lower aspect ratio (smaller sidewall). If this weren't the case, your speedometer would be off.
In years past, one of the ways that people would improve the performance of their sporty cars was to go "+1" or "+2" - this meant increasing the wheel size by one or two inches and picking a tire with a lower aspect ratio to maintain the same diameter.
The reason for going +1 is that tires with a lower aspect ratio deform less under hard cornering and can maintain more of the contact patch. The original trade-off for going +1 or +2 was a harsher ride.
As is so often the case, something that began as a performance item (e.g. spoilers) soon was adapted to be "eye candy" for the street. Tire technology has gotten better too -- if you tried 1980's tires on some of the silly 24" rims you see today, your fillings would rattle out.
It would be silly to pick 20" wheels over 18" wheels for cornering performance in a JGC - you're unlikely to be taking it to the track where something would matter; however it's certain NOT silly to prefer the look of the 20" wheels. For the record, I like the look of the 20" wheels too.
Since I am planning to take my Jeep off-road though, I prefer the functionality of the 18" wheels with the higher aspect ratio tires.