Just come back from a 2000 mile trip through France and was able to check and adjust settings on the Hagon shock that I have. I found the best setting for my 90 kg bulk was preload set at 12 thread spacings from the top and the rebound set at 1 1/2 turns of the screw clockwise from the stop. It took some time but the difference is remarkable . It just needs a lot of miles to stop check adjust start check etc. Maybe of some use - the road usage was not highway but mainly small roads and as twisty as they come.
NO it is a C spanner job , bit tricky - I tend to use a 3/8 extension bar and a hammer. The allen key rebound adjuster needs a dab of copaslip on it to protect it (although it doesnt protrude ).
You could always eat cakes and drink beer for a fortnight - probably the easiest option
Linear Mode
