Instinct knocking noise (no, it's not chain slap)- Mtbr.com
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  1. #1
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    Upset Instinct knocking noise (no, it's not chain slap)

    What's up guys! I have an issue with my '19 BC edition Instinct. I get a knocking sound from the rear end on successive "chattery" hits. Such as repetitive roots, etc. There is no chain slapping on carbon, and I honestly don't believe it is chain slap. I'm not new to carbon full suspensions at all, so I know the chain on carbon slapping sound (which then leads me to follow up with Mastic tape).

    The pivots all seem solid. The rear axle is tight. I've run two different rear wheels with the same noise. I've tightened everything to spec (multiple times). I've heard about some out of spec DU bushing from Fox, but I can't feel any movement at all by wiggling the shock.

    Any ideas? I have seen this discussed in the forum but without any definitive answers.

    Thanks!

  2. #2
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    I've put a few foam blocks along the top of my chainstay and it made it a lot better but I do still get the odd knock on big successive hits but I still think my last bit of noise is still just chain slap. Some have suggested the chain guard and I have thought of doing a run without it.

  3. #3
    Jii
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    Mine knocks too. All pivots and shock bushings/hardware nice and tight. Tried without the chainguard but didn't help. Figure it's got to be chain slap, since it's always when I'm in the higher gears (smaller cogs).

    E: gotta check if I can get away with shortening the chain by a link and see if that helps.
    Last edited by Jii; 01-15-2019 at 03:02 AM.
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  4. #4
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    This is chainslap. Had the same issue with my 2018 BC Edition, there is only minor clearance between chain and frame. I just use now a Lizzard Skins neoprene protector and all knocking noise is gone.

  5. #5
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    I think the knocking has to do with the DPX2. Back when the 2019 Fox service information came out, there was a note on their website that the 2019 shock piston band fixes the "knock" issue. If you compare the 2018 vs 2019 drawings on Fox's website you'll note that they now require the piston (mid valve) band to be measured with a funnel and adjusted with a press (fox proprietary tools).

    My X2 BC edition no longer makes the knocking noise, but I concede that I added mastic tape to the chain stay and to where the brake cable crosses on the inside of the chain stay.
    Last edited by skileh; 01-16-2019 at 10:42 PM.

  6. #6
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    Hmmm... Interesting... I need another shock to test.

    And I understand people saying it could be chain slap, it's just bizarre if that's the case for this noise. Also, I have removed the chain guide to see if that would help. It didn't.

  7. #7
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    Diagnosing noise like this is a PITA, but I'd check the following:

    1. Feel for play in the shock hardware, including the Ride9 chips. If there's no detectable play:
    2. Increase platform/compression damping on the shock and see if things get worse. If yes, it's the shock, if not:
    3. Check the swingarm and chainstay pivot for a loose bolt. You can usually trigger this one by compressing the suspension once, hard, and then putting pressure on the forward crankarm while locking the back brake. If that's silent as well:
    4. Tape some foam or bubble-wrap around the chainstay and see if that removes the last bit of chain slap.

  8. #8
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    Quote Originally Posted by eric View Post
    Diagnosing noise like this is a PITA, but I'd check the following:

    1. Feel for play in the shock hardware, including the Ride9 chips. If there's no detectable play:
    2. Increase platform/compression damping on the shock and see if things get worse. If yes, it's the shock, if not:
    3. Check the swingarm and chainstay pivot for a loose bolt. You can usually trigger this one by compressing the suspension once, hard, and then putting pressure on the forward crankarm while locking the back brake. If that's silent as well:
    4. Tape some foam or bubble-wrap around the chainstay and see if that removes the last bit of chain slap.
    Thanks for the tips!! I really appreciate it!

  9. #9
    Jii
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    Quote Originally Posted by Boover View Post
    Hmmm... Interesting... I need another shock to test.
    I have the non-BC Instinct with the DPS so itís the shock only if both models knock.

    However, this thread inspired me to get a neoprene chainstay guard and test if that lessens the noise.

  10. #10
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    Quote Originally Posted by Jii View Post
    I have the non-BC Instinct with the DPS so itís the shock only if both models knock.

    However, this thread inspired me to get a neoprene chainstay guard and test if that lessens the noise.
    Does your non-BC Instinct also exhibit this knock issue?

  11. #11
    Jii
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    Quote Originally Posted by skileh View Post
    Does your non-BC Instinct also exhibit this knock issue?
    Yup, see message #3

    E: Remembered that this issue was brought up earlier too (by you) but apparently there was no fix other than the suspicion that the shock's the culprit?https://forums.mtbr.com/rocky-mounta...l#post13723412
    Last edited by Jii; 01-17-2019 at 12:54 AM.
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  12. #12
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    Add some additional chainstay protection and hit some chatter at speed, but in the largest gear. If noise lessens you know its slap. I thought something was broken with my c70 and it was slap.

  13. #13
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    I'd imagine with the 50t cog there will be chain slap considering how long the chains must be in the lowest gear. No clutch can make up for it.

    I really hope that mine doesn't, I just bought a '19 BC Edition in alloy and those kind of noises make me overthink everything. There are factory chain slap "blocks" over the chainstay that might muffle the sound, but maybe make a different noise.

    One thing's for certain, I'm gonna miss the feel of my Shimano 11 speed XT drivetrain... But I wanted the BC for the suspension, so hopefully the DPX2 doesn't have a chronic issue that makes a knocking noise.
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  14. #14
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    Likely to be chain slap. Friend with altitude changed the shock, linkage and still knocked. In the end wrapped shit out of the chainstay and got rid of 90% of the noise.

  15. #15
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    I had a terrible noise on my 2019 Instinct. With the bike stationary, If I pushed down on the saddle to emulate movement I heard this clicking type noise. The shock came out, checked connections etc. Wasnt that. Shop had it, pull all pivots out and regreased. Not that. They looked at various other things.

    In the end it was a cable tie that was too tight on the rear cable!!

  16. #16
    Jii
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    Quote Originally Posted by Jii View Post
    However, this thread inspired me to get a neoprene chainstay guard and test if that lessens the noise.
    Update: No knocking noises since I installed the chainstay guard.
    RM Instinct C70 2019
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  17. #17
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    Quote Originally Posted by Boover View Post
    What's up guys! I have an issue with my '19 BC edition Instinct. I get a knocking sound from the rear end on successive "chattery" hits. Such as repetitive roots, etc. There is no chain slapping on carbon, and I honestly don't believe it is chain slap. I'm not new to carbon full suspensions at all, so I know the chain on carbon slapping sound (which then leads me to follow up with Mastic tape).

    The pivots all seem solid. The rear axle is tight. I've run two different rear wheels with the same noise. I've tightened everything to spec (multiple times). I've heard about some out of spec DU bushing from Fox, but I can't feel any movement at all by wiggling the shock.

    Any ideas? I have seen this discussed in the forum but without any definitive answers.

    Thanks!
    I have the same issue with my 2018 with a fresh 2018 fox x2 shock. Following for a response.

  18. #18
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    Quote Originally Posted by Jii View Post
    Update: No knocking noises since I installed the chainstay guard.
    which guard exactly did you get?

  19. #19
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    Which rims do you have? Sometimes the welding plate inside can get loose! Not a problem for safety at all but extreme annoying. Can be solved with glue.


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  20. #20
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    Wow! Just looped an old 26" tube around my chainstay and all noise disappeared. Happy as.

  21. #21
    Jii
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    Quote Originally Posted by lucifuge View Post
    which guard exactly did you get?
    Just a generic neoprene one. I've since taken it off and the knocking came back
    RM Instinct C70 2019
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  22. #22
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    Having a really terrible knocking noise on a Rocky Mountain Altitude, pretty frustrated at this bike. It is my brothers bike and ive never had noises like this thing is making. It sounds like the bike is doing damage at the rear end. I have added some chainstay protection but havent gotten too crazy with it yet. I may try the neoprene guard, I torque the pivots after every ride to check, sometimes the shock bolts loosen just a hair, wonder if their spec is a little low.

  23. #23
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    I have a 2020 Instinct BC70 and have lots of noise too. Anyone though of, or used, one of these: https://chaintameruk.co.uk/

  24. #24
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    I bought these 3M rubber feet from a local electronics store today. I will see how they go. The actually sit really flush on the chainstay even though it looks like there is a gap! Hopoefully this will silence things on my 2020 Instinct BC.

    Instinct knocking noise (no, it's not chain slap)-img_9155.jpgInstinct knocking noise (no, it's not chain slap)-img_9156.jpgInstinct knocking noise (no, it's not chain slap)-img_9157.jpg

  25. #25
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    When I was changing the ride 9 chips I noticed the chips fit in a little on the loose side, I decided to pack it full of grease and am going to ride and see if that helps at all.

    Where have people seemed to settle on their ride 9 positions on Instincts and Altitudes? My Altitude has been in Position 1 and 5, and now I just moved it to 3, Position 1 was too progressive but I wanted it a little slacker than P5.


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  26. #26
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    For anyone with a loud suspension knocking noise, check to make sure the conical washer is in place under the frame shock bolt. Without this conical washer there is play in the shock mount even when the bolt is torqued tight. A friend's Altitude was missing this washer and he chased the rattle even after getting the shock rebuilt.

    Instinct knocking noise (no, it's not chain slap)-altitude-shock-bolt.jpg
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  27. #27
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    Quote Originally Posted by lucifuge View Post
    I had a terrible noise on my 2019 Instinct. With the bike stationary, If I pushed down on the saddle to emulate movement I heard this clicking type noise. The shock came out, checked connections etc. Wasnt that. Shop had it, pull all pivots out and regreased. Not that. They looked at various other things.

    In the end it was a cable tie that was too tight on the rear cable!!
    @lucifuge which cable tie? That clicking noise is driving me crazy. The noise sounds like it is coming from where the DPX2 connects to the frame. But I've had my '19 Altitude C50 apart, meticulous cleaning, regreasing, etc trying to solve this. One person on a diff forum said that it was the bolt (#14 in the image below) to sleeve (#15) clearance. But before I spend money replacing those, I wanna see if it's this cable tie you speak of.

  28. #28
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    Quote Originally Posted by Hemi345 View Post
    @lucifuge which cable tie? That clicking noise is driving me crazy. The noise sounds like it is coming from where the DPX2 connects to the frame. But I've had my '19 Altitude C50 apart, meticulous cleaning, regreasing, etc trying to solve this. One person on a diff forum said that it was the bolt (#14 in the image below) to sleeve (#15) clearance. But before I spend money replacing those, I wanna see if it's this cable tie you speak of.
    Hi, I'm at work so i cant check at the moment. But from memory on the non-drive side of my 2019 C70 there is a cable that nuns along the underneath of the chainstay. (Brake or gearing I cant recall). Anyway, on my actual bike there were small cable ties attaching this along the chainstay. At least one was so tight it disallowed play and caused shocking noise. What was amazing at the time was that shop basically undid the entire bike and it was the last thing they checked. As noise travels it was impossible to locate earlier. I cant comment as to whether these cable ties are factory or was done by the lbs..so maybe not every Instinct has them? So maybe your bike doesn't have them, pls check. At the time, I could push down on the saddle and replicate a click on every depress! Incredibly small and annoying thing to have caused it.

    Having said all that I read so many threads of noisy DPX2 that I went an X2 for my upgrade over my little DPS!

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