Post Master General
Join Date: Apr 2012
Location: Bowling Green, VA
I Ride: '09 ZX6R
USD forks have less flex than conventional designs. If the mass of the bike/rider combination remains similar, the loads applied to the frame wouldn't change significantly.
Think of the forces involved in a stoppie... Right on the edge of skidding the front, ~600 lbs on the front contact patch, which is a lever ~3' long ---1800 lbs of force presuming the surface is uniform. Add a pothole to the mix and take a guess on how much the peak load may be on the steering neck.
ALL of that potential energy has to be handled by the two sets of bearings, before you have to worry about frame flex.
Between the wheel, the steering neck bearings and fork tube flex....... loose bearings are a much bigger contributor.
Dirt bikes have been running USD forks for many generations without destroying the frames of the bike..... I think supercross probably puts an equal or greater load on a much lighter frame..... Less mass, but longer fork to lever the forces...
"Basic stuff fellas. Use your head for something other than to break your next fall."