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I'm playing around with my Revelation Dual Air U-turn fork right now. It has two shock pumps connected to the pos and neg chambers. When I compress the fork, the gauge for the pos chamber goes up, and the gauge for the neg chamber goes down. So as the fork is compressed, the pos pressure increases and neg pressure decreases. It really does seem to work like a "negative spring". But I'm confused as to why.

Previously I though the pos and negative chambers were analogous to two coil springs with different coefficients stacked on top of each other. I'm not sure how to reconcile this with the physical structure of the dual air cartridge, which (as I understand it) is just a tube with a floating piston in the middle, with both sides pressurized. In order for the bottom chamber pressure to decrease as I observe, the volume of the bottom chamber must be increased as the fork is compressed. At the same time, the volume of the top chamber must be decreased to create the observed pressure increase. How is this accomplished?

I know it's been discussed a few times on the board but I haven't found a thread that concisely explains the dual air workings (some posters can't seem to agree on the basic workings).
 

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as you said the piston is floating and attached/fixed to the lowers, so when the fork compresses the stanchions go into lowers, causing what you described the positive chamber gets smaller and the negative gets bigger.

the negative air chamber is called like that because it IS a negative air spring
 
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