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  1. #1
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    Fox Float R Cavitation

    I've got a 2007 Fox Float R that sounds like it's cavitating if I dial in a faster rebound.

    I change out the seals, etc pretty regularly. Is it time for a Push overhaul or something?

  2. #2
    Save Jesus
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    You cannot cavitate these shocks on the rebound stroke, only the compression stroke.

    Take off the air can.

    Orient the shock with the thin shaft up.

    Push down on it.

    If it makes squishy noises, you have air in the oil section, so you need to send it to Push or any of the other suspension tuners.

    If the shaft pushes down easily and doesn't try very hard to push back up, then you have lost IFP pressure. This could also allow small air bubbles in the oil to expand. You might be able to get away with recharging the IFP pressure only and that will re-compress the bubbles in the oil section. A local tuning shop that works on other fox dampers like ATV or etc may be able to do this service.

  3. #3
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    Re: Fox Float R Cavitation

    Took off the air sleeve and did your test. No issues there. Takes some effort to compress and all the rebound settings work as expected - with no noticeable "slurping" sound that might normally be associated with cavitation.

    So maybe I've got a bad seal somewhere on the air sleeve?

    Ideas?

  4. #4
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    Re: Fox Float R Cavitation

    I threw the shock back on the bike without the air canister and actuated the suspension. There's definitely some sound coming from the piston. It almost sounds like a dry seal, but again, everything is working as expected, just that weird noise on the rebound stroke.

  5. #5
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    Take the shock back off the bike, and leave it in the small shaft up orientation for a few minutes without touching it. If there are small bubbles in the oil, they will rise to the top. Then actuate the shock only in the first 3/8" worth of travel and listen for noises. If no noises, the core of the shock is fine.

  6. #6
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    Re: Fox Float R Cavitation

    I'll give it a go. Thanks.

  7. #7
    Vorsprung Suspension
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    Quote Originally Posted by beanbag View Post
    Take the shock back off the bike, and leave it in the small shaft up orientation for a few minutes without touching it. If there are small bubbles in the oil, they will rise to the top. Then actuate the shock only in the first 3/8" worth of travel and listen for noises. If no noises, the core of the shock is fine.
    Good call - while doing this, check if the sound is happening consistently or not - if it's very consistent at the very top of the stroke, the noise is most likely coming from the hydraulic topout circuit, which is fine. If it's inconsistent and doesn't happen every time, then you have air in the oil, which can be a sign of needing a service or just a dodgy factory bleed. The FOX fill and bleed method is not particularly thorough and it is very common to find brand new shocks with quite a bit of air in them.

    Other than that, with certain valve configurations, it is normal for the shock to make a sucking noise during the rebound stroke - this is a byproduct of certain flow characteristics, even with a perfect bleed. FOX use fluted rebound needles in their FIT cartridges to cut that noise down, but such needles are not used in their rear shocks.
    VorsprungSuspension.com - fully engineered suspension retuning & servicing in Whistler, BC.

  8. #8
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    Re: Fox Float R Cavitation

    Ok, just tried this again. No sound at all with the air sleeve off and testing as directed. Absolutely no sound and smooth as a baby's bottom.

    Put the air sleeve back on, added the right amount of Float Fluid, pressurized the air spring and set the rebound to it's slowest position and then backed off five clicks.

    Sound is still there and definitely happening on the rebound. I had my son actuate the suspension while I listened.

    Just like I mentioned before, the faster the rebound, the more noticeable the sound. But, the shock seems to function normally. ??

    All the seals are pretty new but it sounds like cavitation. That's the best way I can describe it.

  9. #9
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    With the air can installed, is the noise right at the top of the stroke? Fox floats can make a "woosh" sound (both rebound and compression) when the air piston travels past the dimple in the air can that equalizes the pos/neg chambers. You can also feel a slight "notch" in the spring force when doing the "lean on the seat" test.

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