The charts are damping force. Notice it's force as a function of velocity. Spring rate would have been force by position.
As for it being linear, that's what modern shocks go for. A simple damper that is just a piston with hole in it will be very progressive. The force will go way up as velocity increases and make the suspension harsh. A shim stack like in a motocross bike tries to make the damping be more linear with respect to velocity. When it moves faster the shims flex and let more oil through, where a simple piston would maintain a more constant flow rate and let the force spike.
It's funny that modern dampers are designed to be less progressive, which is the opposite of what most people think. But it does make sense. You want the suspension to move fast when it hits a sharp bump. If it tightened up at high speeds it would be harsh on square edged bumps and mushy on rollers.
Josh Vanderhoof
Sole Proprietor jlv@mxsimulator.com
If you email, put "MX Simulator" in the subject to make sure it gets through my spam filter.
