Fak… ok. The bitchin HD5 is a far cry from fun still. It climbs well but the suspension is lifeless. So I decided to open up the fork and see what we could change…
All this Ibis tune is..
they basically took two shims off the rebound stack.
And they increased the range of adjustment of the base valve float.
Taking two shims off the rebound does next to nothing in this Fox design. It reduces low speed rebound damping but does so in what was designed as the high speed circuit. So essentially they just made low speed rebound next to zero and did not address high speed rebound at all…The rebound is still too slow when you need it fast and too fast where you need it slow…
Ok.. so also, (compression) generally you never give a base valve any float at all. The base valve is just to control low speed damping forces really precisely. The oil flow is really low. And the forces are really low at higher speeds already. If you want to change the forces of that valve you need to change the shims. By adding “float” they basically just made a big hole and just make it useless. The effect here is no control entering corners and a dead feel at slow speed pops.
Fox just did not make this easy. There are no usual shim stacks in this fork and no easy way to model it… so trial and error…
This is the 3rd iteration of my work. The previous two rounds were focused on reducing the force of the single 0.1mm rebound shim backed by the keeper and “leaf spring” of this lame ass design…
Today…
I added bypass into the high speed rebound circuit by installing a too small face shim… For tuning the added float can be compensated for with closing the low speed bypass circuit. This was the simplest method I could devise with this Fox design. It’s super fast now. (I think in the future I may flip the valve upside down and see how that works.)
I also reduced the float in the high speed mid valve compression circuit to give back some “pop” (reduced OEM float by 0.1mm.) The concept was this: the low speed rebound bypass will be closed more to compensate for my change (increase) to the rebound stack bypass. With that closing of the mid valve bypass circuit via the low speed compression needle a small change in compression stack float will make a big difference to high speed forces.
On the base valve I rebuilt the stack into a two stage stack. And removed Ibis’ added “float”. This is just the proper way to work with a base valve. Two face shims instead of four are now separated by a 0.1mm cross over. I should be able to run with the “high speed” adjuster knob turned way in now…
Looking forward to testing.
As Much Dirt As Possible 