According to FOX published in Pink Bike article quoted here verbatim
Source:
http://www.pinkbike.com/news/To-The-Point-Rebound-Damping-2013.html
The order of setup should always be: measure sag, adjust spring until proper sag is attained, adjust rebound, adjust compression damping. This follows the order of importance of each element: the correct spring rate is the most important, then the correct rebound setting, then
the compression setting.[end quote]
ABOUT REBOUND
Don’t trust that the person at the demo booth or shop did it correctly. If they ask you for your weight, and don’t measure sag, they are doing it wrong. If they change the spring pressure and don’t check rebound, they are doing it wrong. And don’t forget to check the tire pressure! Tires can have a huge impact on how suspension feels. [end quote]
If rebound is set too fast, it will result in your wheel falling into more holes, instead
of skipping over the top of them, as it should. It will result in a bike that feels skittish and
uncontrolled, and will be scary off of jumps. You will get bucked, you will bounce upon
landing (even if you kept it rubber-side-down), and it will be a wild ride. At high lean angles
it can result in loss of traction. [end quote]
If rebound is set too slow it can “pack down,” where successive hits result in the wheel
getting deeper and deeper into the travel. This will result in not having enough travel to
deal with subsequent hits. Most people don’t realize that a symptom of too much rebound
damping is harshness on compression. This is due to the bike riding deeper in the travel,
and your hands and feet working against higher forces in the springs. A common fix for
harshness is to reduce compression damping, but if you are packing down, it will exacerbate
the problem. Another symptom of slow rebound is your bike sitting too deep in turns
(especially fast berms). If your bike has the rebound set properly, you won’t be thinking about
rebound while you are riding.[end quote]
There is a very limited range of rebound velocities that result in a good setup. Some
people may prefer rebound on the slower side of this spectrum, and some on the faster side.
This is worth repeating: the useable spectrum for a given rider is only about 3 clicks wide. [end quote]
...in general, rebound damping is much higher than compression damping and rebound shaft velocities are about one-third of compression velocities. [end quote]
Ok that FOX article was great but........
Second article http://www.sportrider.com/tech/146_9608_tech/viewall.html
From the second article:
The fundamental difference between compression and rebound velocity profiles is due to the fact that compression is forced by the shape of the bump, while rebound, though affected by other forces, is pushed mostly by the spring. [end quote]
This means that, for compression damping, the shape of the bump is far more important than its size. A square-edged bump results in extremely high shaft velocities, while even a big dip will typically cause fairly low velocities. [end quote]
Now definitions in the third article:
http://www.cyclemonkey.com/suspension_101.shtml#Compression%20Damping
Compression Damping
Controls the speed at which the fork collapses
or compresses as it encounters an obstacle. Too little compression
damping (fork moves too fast) and the fork will go through all its
travel on smaller sized bumps and bottom out. Too much compression
damping and the fork will feel harsh and will not achieve full travel.
Some forks offer this as an external adjustment while others are pre-set
from the factory. Those forks without external adjusters can usually
be adjusted internally if necessary. Additionally, many of the forks on
the market intended for more aggressive riding will have two external
compression adjustments: high and low speed.
High-Speed Compression Damping
Controls the motion of the fork during high shaft velocities such as large impacts or sharp/sudden impacts. This adjustment can be used to reduce bottom out (higher/slower setting) or reduce spiking during sudden impacts (lower/faster setting).
Controls the motion of the fork during high shaft velocities such as large impacts or sharp/sudden impacts. This adjustment can be used to reduce bottom out (higher/slower setting) or reduce spiking during sudden impacts (lower/faster setting).
Low-Speed Compression Damping
Controls the motion of the fork during low shaft velocities such braking and small bumps. This adjustment can be used to reduce brake dive and wallowy feel (higher/slower setting) or make the fork more sensitive to small bumps and track better in loose conditions (lower/faster setting)
Controls the motion of the fork during low shaft velocities such braking and small bumps. This adjustment can be used to reduce brake dive and wallowy feel (higher/slower setting) or make the fork more sensitive to small bumps and track better in loose conditions (lower/faster setting)
Rebound Damping
Controls the speed at which the fork opens or
rebounds after it has hit an obstacle. Too little rebound damping (too
fast) and the fork will open too quickly, possibly bouncing the wheel
off the ground, throwing the rider off balance, or providing poor
traction. Too much rebound damping (too slow) and the fork will not
open fast enough to respond to the next impact and will give a harsh
ride. It will not have reached full extension before the next bump and
will move further and further into the travel until it gets to the end
and has packed up. Try adjusting the rebound knob so that the fork is
as fast as possible without feeling uncontrolled. Alternatively, have a
friend watch you ride off a curb, seated, and adjust the rebound so
that the fork bounces exactly once.
