[Ducati Scotty]

It's all about trail.

http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometry

Wikipedia did a bang up job on this one.  Trail affects the handling of a motorcycle more than any other geometry factor.  Basically the contact patch of the tire is behind the pivot axis of the steering head.  This is just like a shopping cart wheel.  Make the trail longer and the bike becomes more stable as the wheel has a longer lever pulling it in line.  By installing a taller wheel in front you tip the front end up, kick the rake out a bit more to the front, and increase the trail.  The bike will probably be noticeably more stable, a little less nimble, and take a little more steering effort.

Scott

[HMR]

Ah so, thanks. So longer travel shocks at the rear with a 21-inch wheel up front should then get me back to more or less normal trail? The regular RE shocks are quite pathetic in the dirt...
http://www.youtube.com/watch?v=zOmvG6Ha9HY

HMR
Mumbai

It's all about trail.

http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometry

Wikipedia did a bang up job on this one.  Trail affects the handling of a motorcycle more than any other geometry factor.  Basically the contact patch of the tire is behind the pivot axis of the steering head.  This is just like a shopping cart wheel.  Make the trail longer and the bike becomes more stable as the wheel has a longer lever pulling it in line.  By installing a taller wheel in front you tip the front end up, kick the rake out a bit more to the front, and increase the trail.  The bike will probably be noticeably more stable, a little less nimble, and take a little more steering effort.

Scott