Dick Burleson has a good tire changing video and a good off road riding technique video - these were done in the mid-90s. The riding one shows him going through a muddy section spinning the rear wheel to keep it "clear"...
Spinning versus not depends on the mud. If it is "gumbo" and is packing up into the knobs - then you spin the wheel to fling the mud off and get better traction. You want to concentrate on keeping the knobbies clear of mud. Also when you get a clear spot in the trail without mud - e.g. road crossing, etc. - you get up to as high a speed possible to clear the front wheel of mud too.
If it is a mud sand mix - or a mud that is heavily saturated with water - it won't stick to the tire much. Max acceleration without wheel spin can be used in this situation.
jeff
|