Rockshox forks dualair positive and negative air pressure settings - Bike Forum

Re: Rockshox forks dualair positive and negative air pressure settings

LoCo — Sat, 31 Mar 2012 09:41:36 +0000

What James siad basically, I tend to run 10 psi mor in the +VE chamber as find them too 'divey' otherwise, unless the low speed compression is increased enough to over come it but them you lose a blittle small bump sensitivity (from lots of low speed) so do it on air pressure.
Other set up guidance can be found here:

http://locotuning.co.uk/tech-info.html

Re: Rockshox forks dualair positive and negative air pressure settings

james — Sat, 31 Mar 2012 09:32:31 +0000

If you fork valves and your shock pump are working properly you shouldn't lose any pressure when you disconnect the shockpump. The air loss you can hear is the air escaping from the shockpump

It is when you connect the shockpump to the fork that some of the air in the fork fills the shock pump equalising the 2, and so it reads less than when the shock pump was last connected

I have found certain shock pumps with certain fork/shock valve combinations not to work properly and can leak on disconnection, could be some element of wear going onm but not sure

Oh and because the +ve chamber will be much bigger than the -ve chamber, the -ve chamber will drop more pressure when connecting to it than when connecting to the +ve

Re: Rockshox forks dualair positive and negative air pressure settings

chives — Sat, 31 Mar 2012 08:41:45 +0000

How are you all measuring 5psi differences in neg pressure?? I reckon I lose way more than that just unscrewing the shock pump.. 8O

Re: Rockshox forks dualair positive and negative air pressure settings

muddydwarf — Sat, 31 Mar 2012 08:10:40 +0000

I have some 2009 Pikes, and i find i have to run them with 15/20psi less in the negative chamber or the forks have a marked tendency to 'suck down' their travel. I can actually see the slow creep of this happening when i equalise the pressures!

Re: Rockshox forks dualair positive and negative air pressure settings

retro83 — Sat, 31 Mar 2012 08:04:18 +0000

jonke - Member
So it sounds like its just a way to change compression damping?

I think I prefer a dial to do this

No it's more like an equivalent to preload adjustment on a coil fork.

I always used to run the neg 5 psi higher than the pos, but on the 2011/2012 forks i think about 5 PSI less works well. Not sure if it's just my tastes have changed or if they've changed the air spring.

Re: Rockshox forks dualair positive and negative air pressure settings

Bazz — Sat, 31 Mar 2012 07:49:09 +0000

I always run about 5psi less -ve as it helps stop brake dive, which i detest.

Re: Rockshox forks dualair positive and negative air pressure settings

jonke — Sat, 31 Mar 2012 07:36:10 +0000

So it sounds like its just a way to change compression damping?

I think I prefer a dial to do this ;-)

Re: Rockshox forks dualair positive and negative air pressure settings

james — Fri, 30 Mar 2012 20:55:59 +0000

+ve and -ve pressures the same, the fork maybe sits a little bit into the travel ('unsagged'/bike not weighted) and dives 'normally'

-ve pressure > +ve pressure, more plush/dive-prone, but sits unto the travel a bit more when 'unsagged'/bike not weighted

+ve pressure > -ve pressure, more firm/skittish, feels like it takes more bump to get it to start moving

10psi difference will make a noticable effect

I sometimes maybe run 5psi more -ve than +ve, but its still a touch dive-prone when pushing it (for me)
It basically gives you more options, though I don't really use them

"More negative pressure = more active initial compression stroke"
More plush/prone to fork dive

Re: Rockshox forks dualair positive and negative air pressure settings

PJM1974 — Fri, 30 Mar 2012 20:48:01 +0000

Less negative pressure - the fork is less sensitive and can feel a little harsh, however it reduces pedal bob and can make the bike sag less.

More negative pressure - the for is more sensitive to terrain at the expense of being more prone to pedal bob. Makes the fork sink a little further into it's sag.

FWIW I always balance the two or run slightly more negative pressure (5psi). Feels better that way innit.

Rockshox forks dualair positive and negative air pressure settings

jonke — Fri, 30 Mar 2012 20:40:14 +0000

Can someone explain this to me?

Whats difference does more or less of the -ve air pressure make? I looked on the Rockshox website which say to start with the same amount of -ve pressue as +ve then adjust to feel and also More negative pressure = more active initial compression stroke.

What is a More negative pressure = more active initial compression stroke?