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Forks that use an air spring, as opposed to a coil spring, have to be pumped up to the desired pressure to work as intended (using a shock pump). From experience, I know that they lose pressure over time. However, I usually notice the pressure drop only after it becomes very apparent, and the time in which this loss occurs seems to vary somewhat, so I do not know what is the normal interval for reinflating forks, or the normal range for such interval. The service manual of my forks (all are RockShox) does not state this interval explicitly. Rather, it describes intervals for more elaborate service procedures (50 and 200 hour service) that involve deflating and reinflating the air spring as an inevitability, so I do not think that they should necessarily be taken as reinflating intervals.

I would like to know this primarily because it would give me an indication of whether my fork is damaged or in good condition (I can always check if my fork is losing air, but without knowing how often this loss normally occurs I cannot tell if the fork is fine or not). So, what is the normal fork reinflation interval?

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  • My shock looses 20 PSI every time I connect the gauge/pump. So I just reinflate it every 3-4 months no matter what.
    – Criggie ♦
    Jan 17, 2021 at 20:20
  • @Criggie that shouldn't happen. What kind of pump are you using?
    – Paul H
    Jan 17, 2021 at 21:23
  • @Paul H Why not? The pump will steal some of the fork/shock’s air to equalize its own internal pressure. Shocks have tiny air volumes, so even a tiny loss in terms of volume will result in a surprisingly large pressure drop.
    – MaplePanda
    Jan 18, 2021 at 1:04
  • To me it suggests a bad seal in the pump. Best I can tell, my repeated connections of my larger RockShox pump only steals about 5 out of 185 psi from my short-stroke (5 cm?) Fox DPS (i.e., no piggy pack)
    – Paul H
    Jan 18, 2021 at 1:08
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    @Jahaziel That’s a good technique to use, and many forks come with an o-ring on one of the stanchions specifically for that purpose. You just need to be aware of how close the seal gets to the crown during bottom out. With some forks, there might not be enough room for a full-size zip tie.
    – MaplePanda
    Jan 19, 2021 at 23:06

1 Answer 1

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For one, it depends on how sensitive you are to changes in suspension performance. You can’t really measure for any drop (your shock pump will initially steal some of the air chamber’s air in order to equalize the pressure), so you’d have to go by feel.

From my experience, leakage has been negligible, even after a few months. Topping the air up isn’t hard anyways, so it’s not a big issue. Just screw the pump on, get back to your original pressure, equalize the positive and negative air chambers (if applicable), and you’re good to go. If your fork/shock leaks faster than that, you probably need to do a service.

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  • I rushed to blab my comment above before reading your answer, which is exactly what I'm saying.
    – Jeff
    Jan 18, 2021 at 9:04
  • Thanks MaplePanda, all sensible points. But I find it weird than no one seems to know the exact, or at least a more precise answer to this question. Is it a month? Three months? Never? Each and every related thread I have read quickly delves into analysis of individual fork air loss problems or concludes that topping up is a simple procedure one should not worry about. On the other hand, Shwalbe tubes, for example, although orders of magnitude less expensive than a good fork, come with a note reminding the users to top them up about once a month. This is an industry oversight in my opinion.
    – Mick
    Jan 19, 2021 at 12:36
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    @Mick A properly sealed fork should go months without significant pressure loss (inevitably, no seal is perfect). Seasonal variations in temperature mean that you would be adjusting your pressure that frequently anyways if you were sensitive to changes that small. Tubes don’t really wear out the same way that suspension seals do.
    – MaplePanda
    Jan 19, 2021 at 23:09

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