From the Reba manual: "More negative air pressure results in a suspension set-up that is more active, especially to small bump input."
As far as I understand, that would be wrong.
What the negative pressure does, is that it strives to compress the fork. With higher negative pressure, the spring curve will start at a smaller force, and then go up to about the same bottom-out point as with a lower pressure, but through a steeper curve. A smaller force will be required to start compressing it from unloaded. And the fork will get more sag.
Now, when you sit on the bike and get that bigger sag, you will be at a steeper point on the spring curve. Therefore, when you hit a bump the fork will not compress as easily. It will be less active. Not more active.
So, if you want a "plusher" ride, you want a smaller negative pressure. Not a bigger. If you then want to maintain 20% sag, you need to decrease the positive pressure as well. Because it's not possible to maintain both the sag and the bottom-out force, and get a more active set-up. You have to compromise at least one of them.
Currently riding my own Reba at 100 pos, 80 neg (160 lbs), and still experimenting.
Should I contact RockShox for an explanation, or did I get something wrong?
As far as I understand, that would be wrong.
What the negative pressure does, is that it strives to compress the fork. With higher negative pressure, the spring curve will start at a smaller force, and then go up to about the same bottom-out point as with a lower pressure, but through a steeper curve. A smaller force will be required to start compressing it from unloaded. And the fork will get more sag.
Now, when you sit on the bike and get that bigger sag, you will be at a steeper point on the spring curve. Therefore, when you hit a bump the fork will not compress as easily. It will be less active. Not more active.
So, if you want a "plusher" ride, you want a smaller negative pressure. Not a bigger. If you then want to maintain 20% sag, you need to decrease the positive pressure as well. Because it's not possible to maintain both the sag and the bottom-out force, and get a more active set-up. You have to compromise at least one of them.
Currently riding my own Reba at 100 pos, 80 neg (160 lbs), and still experimenting.
Should I contact RockShox for an explanation, or did I get something wrong?
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