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  • RS Revelations; knocking sound!? Please help!
  • HermanShake
    Free Member

    Hey, I’ve recently developed play/knock when my fork is extended (mild trails with small bumps). I run 80 psi in both chambers. If I hold my front brake down and rock my bike front and back the knock appears.

    I hadn’t used it for a while (month-6 weeks), not topped the air up and it appeared. Then added 80 to each chamber and the same appeared. It rides fine, but I don’t want to fudge up my fork. I couldn’t remember if there’s an order to inflating the chambers, I did lower first.

    Haven’t serviced yet, but also haven’t ridden particularly harshly! Bike (Meta 5.5) is about 18 months old, regularly cleaned and not abused.

    z1ppy
    Full Member

    U-turn’s? They apparently knock….Sorry have to ask, you have checked it’s not you headset???

    Orderwise to setting pressure, top (postive) first, then bottom (negative) IIRC.

    bigjim
    Full Member

    Mine do it too, i think the left bushing needs replacing, I can’t be bothered paying so much though so might just run them into the ground.

    First check its not your headset and then holding the junction of stanchion and slider recreate the knocking sound, if you can feel movement between the two then that’s what I have and i think it must be the bushings.

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    jonb
    Free Member

    Are you not supposed to do upper first?

    Mine knock slightly if the pressure in the lower chamber has dropped. Something to do with them topping out. There’s something in the instructions about adjusting the rebound as well.

    CaptainMainwaring
    Free Member

    Absolutely definitely upper +ve chamber first. Lower chamber first will suck the forks down so you’ll be setting the +ve chamber effectively with the fork compressed. You will end up with way too little air in the +ve.

    And second the comments about checking your headset for play which may be the knocking sound

    Neb
    Full Member

    My RS pikes do exactly the same thing. I’ve read that its play in the thread of the u-turn adjuster. It only happens when the fork is not at the end of its u-turn range. When it is either fully extended or retracted the u-turn adjuster is locked in place against the end and can’t rattle.

    Its bloody annoying tho!

    PeterPoddy
    Free Member

    Probably needs a service by the sounds of it. TFT & LoCo will resize the bushings as part of a normal service. It’s VERY rare they actually need replacing 🙂

    takisawa2
    Full Member

    Does it do it with the fork at max & min travel ?
    If not then welcome to a “feature” of RS U-Turn air forks that doesnt make the sales brochure. Its play in the helix that controls the u-turn. If run at extents of travel the helix is held firm, in between it clunks. Doesnt affect performance, on mine it seemed to pretty much dissapear unless riding very slowly. (Common occurence for me).

    HermanShake
    Free Member

    Thanks for posts so far, BTW they’re not U-turn they’re MoCo lockout. I’m pretty sure it’s not headset but will check.

    I’ll sort my air out, check out the headset then wiggle the lot about to see if it seems like a bushing.

    RE topping out, I thought that’s what may be going on; it feels like it happens when the chambers are neutral (neither acting on the fork). When bigger bumps/compressions occur, the knock doesn’t.

    Judging by the manual recommendations, I’m probably due to service and would want to do so myself. Do air forks need servicing more than coil and oil? Any one else here done theirs?

    Cheers 😀

    bigjim
    Full Member

    I’ve done the lowers and was going to do the moco and u turn bits until I noticed the knocking on mine. I don’t want to send them off for a service though as I’m keen to do it myself (plus I’m a tightarse!). Not sure if there is a way of adjusting teh bushings without the magic tool though.

    nuke
    Full Member

    Since they’re not u-turn, worth doing this test as advised by TFT…stick your finger between the fork crown and the stanchion then rock the bike back and forward with the front brake on: can you feel your finger being pinched? If so, it’s the bushings.

    On the matter of the u-turn helix, I love to know a solution as the slight knocking on my Reba U-Turns is annoying. Having said that, I’ve had 2 sets of Rev U-Turns and a set of Pike U-Turns and never noticed a knocking on them.

    HermanShake
    Free Member

    FFS!! I can’t believe it was so bloody simple. One of the calliper mount bolts had loosened about half a turn and therefore was the problem.

    Well, I now know lots more about the fork and don’t need to service them…yet.

    Thanks again everyone, Mamma mia what a tit! 🙄

    Northwind
    Full Member

    I once became convinced some massive chunk was about to fall off my motorbike because of the horrendous crashing noise it made over every bump. Checked every bolt, swapped parts around, generally agonised over it for a week then realised I’d left the massive padlock from my chain attached to the steel luggage rack :mrgreen:

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