I'm confused. Isn't low speed for big hits, jumps and high speed for stutter bumps and whoops? After reading some of the other threads here about how people set their shocks up it just doesn't make sense to me.
Thats right on... your fine.. However most people confuse this stuff, Also the low speed interacts with the high speed and most ametuer tunners confuse low speed stact with high speed compression..
I read in Eric Gorr's book (Motocross and Off-Road Motorcycle Performance Handbook) that "The low-speed circuits work in two common track sections: braking for tight turns and accelerating on a straight with far-spaced, shallow whoops." and that "The high-speed circuits work in two common track sections: landing from big jumps and accelerating on a straight with tightly spaced, sharp-edged whoops."
So, I've been thinking I need to increase my forks HSC dampening to help prevent harsh bottoming when landing from big jumps. Is this correct?
My understanding is that jump landings are usually a low to midspeed issue. That being said, I "think" that the HSC clicker (shock) works in the lower range of the high speed circuit, if that makes any sense. Basically you are correct in your first assumptions, but so is the info in Eric's book. As Jer eluded, all the circuits overlap to a degree, and effect the external adjusters (clickers) range of operation.
Anssi is also correct, you must first be sure that your spring rates and sag settings are correct, then move to clickers, then valving (in that order).
With regards to your forks bottoming, have you tried raising the oil level? This will decrease the air chamber and help firm fork in the last 1/4, or so, of travel. Virtually cost free and works to some degree.
Please, I am no expert, so feel free to correct me if I am wandering.