On Thu, 29 Jan 2009 17:17:50 -0800 (PST), Chalo
wrote:

But why dod you need more for rim protection when going fast? Or
shock absorbtion? Or wear resistance?

Because the energy contained in bumps goes up as the square of the
speed. It's four times easier to pinch flat or flat spot a rim at
30mph than at 15mph.

Bumps have only a horizontal component? Interesting.