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

[548swimmer]

Originally Posted by Chris is me

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.

Unfortunately, in the case of polymers, this is not a misconception. On a microscopic level, polymer-based materials (such as the rubber on wheel treads) have "knobs" that protrude and grab on to the microscopic "hooks" of fibrous materials (such as carpet). For this reason, increasing the contact pad increases the number of "knob" to "hook" interactions, which in turn provides an increase of traction. Idealistic entry-level physics states that F=uN, and so as long as the normal force and coefficient of friction remain the same, (it is commonplace to assume that surface area has no affect on the coefficient for basic physics because the other equations are far to complex for classroom labs) no change in frictional force will occur, regardless of the surface area.

Think of it like Velcro. What's harder to pull straight off, one hook grabbing on to one loop, or one inch of hooks on one inch of loops.

"F= uN" is physics

To build on what Ether said, this is only a rough approximation of the resistant force felt by an object, and lumps together everything from microscopic surface roughness to how deep one object sinks into another (e.g. a marble on carpet). There are, however, many other equations that these factors into account.

Sorry if this repeats any of the information on the linked threads, it's just nice to have all the important information in one place.

EDIT:

big1boom got to it first