What's the effect of changing fork oil level?

[McRider]

Changing fork oil level seems to be a tuning option, but I'm not sure what it does. It seems to me the only change would be in the amount of air being compressed in the fork tube as the fork approaches bottoming. Thus you could get a more progressive spring action, and more resistance to bottoming. However, this would seem to be pretty minimal since the range from maximum to minimum oil level specified in the service manual is so small. I guess my basic question is: what problem would you be trying to solve by changing fork oil level, and does it work with the KDX?

 

[bradf]

You pretty much have it. Oil level changes can be felt. Changing from 85mm to 120mm creates more air cushion so the initial movement of the forks is easier, softer. Riding a very slow rocky trail (sharp edge bumps) could warrant this. It is a fine tuning rider preference adjustment.