Losing air in Rockshox Revelation.
widge34
Posts: 900
My Revelation RLT fork is losing air from the bottom chamber. Has the o ring blown? I have only had the fork 3 weeks from new.
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Widge.
Bird Zero 2
Trek Madone 3.5c H2 2013
Widge.
Bird Zero 2
Trek Madone 3.5c H2 2013
0
Comments
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How have you discovered the air loss?0
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Riding today. Forks felt a lot softer. Tried air pump on bottom chamber, reading zero, pumped it back up to 100psi. Top chamber was still fine. Reached bottom of run i was on, tried pressure again, bottom chamber back to zero.----
Widge.
Bird Zero 2
Trek Madone 3.5c H2 20130 -
Losing negative air will make the fork feel harder, not softer (it opposes the main air spring).
When you attach the pump the reading will be less than before as the pump is inflated by the very small negative air chamber.0 -
So if i am pumping the - air up to a 100psi why is it reading zero 5 mins later?----
Widge.
Bird Zero 2
Trek Madone 3.5c H2 20130 -
Because the air is going into the pump, reducing pressure in the neg chamber to one that the pump cannot read. Very common with small high pressure chambers.0
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So is there a problem with the forks or not? I'm a little confused now? Surely if i put 100psi into the forks, next time i attach the pump it should be reading something around 100psi----
Widge.
Bird Zero 2
Trek Madone 3.5c H2 20130 -
No, for the above reasons. The air migrates into the pump body when you attatch it. If the pump body is 4 times as large as the negative air chamber, then the reading will be unmeasureable now. When you unscrew the pump the hiss you hear is the air coming out of the pump that was in the neg chamber. But if you inflate back to 100psi, before you unscrew, 100psi it will be. Pumps are designed to measure the pressure after inflation, not before it.
The problem from your description seems very unlikely to be a neg chamber prob. As above, the fork will feel firmer, not softer (to start).
Reinflate the forks and make sure tha damper setting are steady.Measure sag. Leave overnight and measure sag again. If the same you have no problems.0 -
Thanks Supersonic. Will check it out tomorrow.----
Widge.
Bird Zero 2
Trek Madone 3.5c H2 20130 -
What about the + chamber? Should the same thing happen with it? As when i attach pump it reads what i initially pumped into it.----
Widge.
Bird Zero 2
Trek Madone 3.5c H2 20130 -
The positive chambe is much larger, so the pressure differential will be much less.
Their could be a problem, but the change is sag will reveal it.0 -
It won't reduce to zero by attaching the pump. It does drop by about 20psi
The pressure will equalize between the fork and pump, so it can't possibly be zero.
If it's reading zero, then that's what it is, you've lost your air.
100psi sound a bit low to start with, especially for negative, which is usually around 10 to 15 psi more than positive.
Have you tried the old "spit on the valve" test, to see if that's the problem?0 -
It depends on the pump! Some cannot measure this low. I lose about 80psi, am off the bottom of the start of the scale. Not saying it isn't leaking, hence the test, but the variations pump to pump are enormous.
Why is 100psi low? You don't know his preferred sag or settings. And it doesn't have to be 10-15psi more, it is entirely personal preference.0 -
I was assuming he was using the pump that comes with the forks. It would have to be a fairly large pump to drop to somewhere near zero.
I only said it sounded a little low, not that it definitely was low. He may only weigh 7 stone.
If it is leaking, I think it more likely to be the valve than a problem internally, but you never know.0 -
It could be, the water on the valve test is a good one.0
