4" vs. 6" vs. 8" wheels. Advantages?

[Chris is me]

Originally Posted by EricH

On width, ideal physics says no difference, while reality says wider is better. I'll let the idealists and the realists argue that one out, preferably by testing.

If you're going to assert reality contradicts physics, please at least cite a source of test results or other evidence. Statements of fact without backing like this are how misconceptions are made.

Anyway, there are a lot of reasons to like smaller wheels. The wheels themselves weigh less, and less of a reduction is needed to achieve the same output properties as a larger wheel. The primary drawback is that smaller wheels require more effort to climb obstacles with - a smaller wheel inherently has lower potential ground clearance than a larger wheel. With proper design this can be worked around - many teams climbed the bump this year with 4" wheels and the bump was a rather aggressive obstacle.