Dumb question about suspension

ChrisEyles

Veteran
Location
Devon
I'm pretty sure this is a stupid question, but I can't figure it out in my head at the moment.

Stiction in an air fork is held to be a bad thing, reducing compliance over small bumps.

Platform damping in a fork is held to be a good thing, increasing pedalling efficiency (especially out of the saddle) and reducing brake dive.

How are the two different? Surely a bit of stiction would give a similar effect to the low speed compression of a platform damper, while any bump with enough force to bypass the low speed circuit damping would be enough to release the stiction in the fork.

Asking as I'm currently playing with an old Marzocchi bomber fork with quite a bit of stiction and it rides really similarly to my Rockshox Revs with lots of compression damping and a light floodgate (which is generally a good thing).

Am I missing something obvious here? Maybe I haven't ridden enough nice forks to "get it"?
 

Drago

Flouncing Nobber
Location
Poshshire
Paltform damping relies, in the main, on geometry for its funtction, rather than any physical energy absorption or dissipation properties. The Giant Maestro is the classic example, where by geometry and making the system fully floating, ie, mechanically isolated from the main frame trhough as system of linkages, that pedal bob as a result of variations in drivetrain input is effectively eliminated.

There is another issue. What is often referred to as 'pedal bob' is actually the contraction of the rear suspension as a result of variations in the input power as the rider stabs merrily away at each pedal in turn. Suspension bobbing up and down as a result of a rider physically bobbing up and down due to poor rider technique and thus directly loading and unloading the suspension is a different phenomenon altogether.
 
OP
ChrisEyles

ChrisEyles

Veteran
Location
Devon
That would all apply to pedalling forces, but (if I understand correctly) not brake dive or other low speed forces acting along the suspension axes, like pumping into a berm. To deal with these you need low speed compression damping (...or stiction?!).

Obviously stiction is non tuneable and you can't turn it on or off with a little lever, but for cross country applications I can't see why it would necessarily be considered a uniformly bad thing.
 
I think it’s something to do with the compression rate, you want your forks to react quickly to hitting bumps, able to react in milliseconds. But you really don’t want them to react to pedaling input, something measured in fractures of a whole second. Platform dampening is tuned to reduce input from pedaling, while allowing rapid reaction to bumps. Stiction messes with forks ability to smooth out rough trails, while at the same reducing pedal input.
 
OP
ChrisEyles

ChrisEyles

Veteran
Location
Devon
If fork travel speed (which would be affected directly by damping) and fork load (directly affected by stiction) are not necessarily well correlated, this would explain why platform damping would behave differently to stiction - which I guess could be the case on rapid but lightly loaded bumps.
 
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