James wrote:

The smaller the wheel the less easily it will
be to pull it over a hard bump. Imagine the
wheel was the same radius as a brick. If you
pull the trailer and the wheel strikes
a brick it will not naturally lift up and
over the brick. Now imagine the wheel radius
is many times that of the height of the
brick. If you pull the trailer and the bigger
wheel hits a brick it will naturally ride up
and over the brick.

Bearing friction is hardly a factor.

"For pneumatic tires on hard pavement, it is
reported that the effect of diameter on
rolling resistance is negligible (within
a practical range of diameters)."

OK, great.

--
underground experts united
http://user.it.uu.se/~embe8573