Quote Originally Posted by Ldub
Most go with a taller sidewall profile (smaller rim diameter) & a little extra width (tire wider than rim) to protect the rim when off-roading.
Most of the time, when playing in the dirt/rocks, tires get aired down to lower pressure to increase traction by enlarging the "footprint".
I've also heard a rule of thumb for airing down/rock crawling etc... is rim diameter is no bigger than half the tire diameter... i.e. 16" rim with a 32" tire.