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  1. #1
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    Listen to my carbon mountain bike frame

    https://youtu.be/_2om1umYsaM

    Take a listen to that video and tell me what you think. Here is some background - new BH lynx 6 bike this year. Its been noisy the entire time I've owned it. Taken if down some pretty rough terrain and is riding really well, just a very noisy bike.

    I've tried all the low hanging fruit - torqued the seatpost to 4.5 nm, the handlebar/head tube clamp up to spec. Put carbon paste in seat tube and on handlebar clamp.

    I can hear it "pop" coming right from the frame about 1/2 way between handlebars and saddle on the horizontal piece of the frame. I can feel the pop right there when I put my hands on it. It always happens after I compress the rear shock and as it goes back into the resting position something seems to cause this pop right there.

    I pulled off the fork and looked inside the frame in the area where I think the pop is coming form and I dont see any cracking or delamination. There are no signs of delamination of the outside of the bike or other signs that the frame is failing.

    Everything that I read says that this pop is not normal and needs to be taken care of - is there anything else on the bike that I can rule out besides the frame itself and is there still a chance the bike/frame is OK?

    THANKS!!!!

  2. #2
    mtbr member
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    I had a headset that got some sand in it that sounded much like your event. Perhaps....
    AKA: G-wat

  3. #3
    Interplanetary Poultry
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    Well, you could get a mechanics stethoscope and find the source of the sound that way.
    Editor In Chief, "Internet Tough Guy Magazine"
    "Home of Chuck Norris' Keyboard"

  4. #4
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    Since you bought it new it seems like a warranty issue.
    Warranty and Service: 949-206-8151, x135

  5. #5
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    Not sure I could hear what you described. I heard what sounds like a ratchet system when the bike goes back to normal position after the suspension is compressed. If you are saying there is a pop sound when you press down then I did not hear it.

    Anyway, as posted above, take it in for warranty.


    Sent from my iPad using Tapatalk

  6. #6
    EAT MORE GRIME
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    yank seatpost out

    bounce frame , same issue ?
    "Put your seatbelt back on or get out and sit in the middle of that circle of death." - Johnny Scoot

  7. #7
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    Look at the shock pivots. They could be making a noise in that area. That's what's moving when the noise happens.

  8. #8
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    Quote Originally Posted by Len Baird View Post
    Look at the shock pivots. They could be making a noise in that area. That's what's moving when the noise happens.
    What should I be looking at on the pivots?

  9. #9
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    Iíd be looking at interface between pivot bearings and pivot bolts. if any preload fasteners on your pivot bearings, check those. id also check cables. sometimes they are getting pulled or pushed through attachments points on frame which can make that sound or if internally routed they can be hitting inside of frame.

  10. #10
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    I think it's the shock pivots. I'd hose them down thoroughly with some sort of spray lube and see if goes away, if it does then go ahead and fix them right.
    I brake for stinkbugs

  11. #11
    ol' dusty lungs
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    Quote Originally Posted by attaboy View Post
    Iíd be looking at interface between pivot bearings and pivot bolts. if any preload fasteners on your pivot bearings, check those. id also check cables. sometimes they are getting pulled or pushed through attachments points on frame which can make that sound or if internally routed they can be hitting inside of frame.
    ^ This. Pull your rear suspension apart. Make sure your linkage bearings are smooth and pivot bolts are tight. Also check your internally routed cables - place a few drops of dry lube like Triflow at entry/exit points and pull the cable back and forth a bit to distribute.

  12. #12
    Mr. Buck E. Fikes
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    Take the seat off the post and do it again. I'm putting my money that it's the rails where they interface with the carcass of the saddle. Just diagnosed the identical sounding issue on a friends bike I had in the shop here. Seat replaced, creak gone.

  13. #13
    All fat, all the time.
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    Quote Originally Posted by Oh My Sack! View Post
    Take the seat off the post and do it again. I'm putting my money that it's the rails where they interface with the carcass of the saddle. Just diagnosed the identical sounding issue on a friends bike I had in the shop here. Seat replaced, creak gone.
    X2 I've had similar noises from seat rail or even grit inside the frame

  14. #14
    Mr. Buck E. Fikes
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    WELL?!! Come on, OP! What's the skinny?

  15. #15
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    Sounds like a loose something. Start by methodically pulling apart and greasing/tightening each bolt/part. Eventually you will find the creak.

  16. #16
    Barely in control
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    Suspension bushings over tightened or in need of lube.

  17. #17
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    Following Up

    Folks,

    Thanks for all of the advice. I decided to call the manufacturer and they too said it probably was the pivot points or the bottom bracket.

    Note: before calling them I carbon pasted the seat tub and handlebar clamps, verified all torque settings on the pivots and seat, and greased inside conduits for the interally routed cables, this did not eliminate the noise.

    So, tonight I opened up the pivot points. All of the pivots that had bearings insde of them looked fine - rolling well and not dirty, so I left them alone. I could still hear the creak with those pivots isolated away from the motion anways so those were ruled out.

    The shock pivots did not have any grease where the pin runs through the assembly - I greased a total of three sets of these types of pivots and the sound disappeared (two on the shock and one right above the BB)

    I think the strange thing about this whole thing is that I was truly amazed how much sound and vibrations travel through the carbon - I could feel a pop in the frame a few feet away from where it was actually originating, literally feel it - so I was a little convinced that the problem was with the frame itself.

    Thanks for the help with my problem. I also incurred another issue during my repair, I stripped a cover to a pivot bearing while trying to remove it. Very sad. It was too small for a T45 and apparently a little too large for a T40 because I below out the sides of the piece when I tried to remove it. Have you guys ever extracted a stripped bolt out of a carbon frame? I figure just use an easy out but I really don't want to mess this up and damage the frame or make it impossible to remove by messing it up worse. See pictures.
    Attached Thumbnails Attached Thumbnails Listen to my carbon mountain bike frame-img_2331.jpg  

    Listen to my carbon mountain bike frame-img_2332.jpg  


  18. #18
    Mr. Buck E. Fikes
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    After all of that, did you at any time try the exact same test you showed in your video with the seat removed completely from the bike, leaving just the post in the seat tube?

  19. #19
    BOOM goes the dynamite!
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    Quote Originally Posted by Oh My Sack! View Post
    After all of that, did you at any time try the exact same test you showed in your video with the seat removed completely from the bike, leaving just the post in the seat tube?
    I wanna see him hop on the pedals and bounce w/o touching the saddle. If it still creaks, I'd be surprised.

  20. #20
    Mr. Buck E. Fikes
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    Quote Originally Posted by noapathy View Post
    I wanna see him hop on the pedals and bounce w/o touching the saddle. If it still creaks, I'd be surprised.
    As would I.

    I have heard a metric shit-ton of creaking pivots, BB's, fork crowns, the works. The only thing I have ever experienced that offers the "ratcheting" sound identical to the OP's video, has been a toasted seat. And I've experienced it numerous times. 'Spose there could be a first time it's not....but I doubt it.

  21. #21
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    Quote Originally Posted by Sewer View Post
    The shock pivots did not have any grease where the pin runs through the assembly - I greased a total of three sets of these types of pivots and the sound disappeared (two on the shock and one right above the BB)
    Three sets? Are you saying that the chainstay pivot did not have ball bearings? The big one above bottom bracket in this picture. That would be very strange.

    https://p.vitalmtb.com/photos/users/...jpg?1425655387

    Anyway - you are not supposed to grease the shock pivots.

    https://p.vitalmtb.com/photos/users/...jpg?1425655118

    From this picture it appears that there is Fox 5-piece mounting hardware. If it is too tight you can loosen it up by slightly sanding the outside of the plastic bushings (How to make Fox bushings better), but you should not use any grease. It is also very important to make sure that rotation happens between the plastic bushings and the pin and not between the pin and bolt - later will ruin your rocker.

    Quote Originally Posted by Sewer View Post
    It was too small for a T45 and apparently a little too large for a T40 because I below out the sides of the piece when I tried to remove it.
    It does not look like Torx to me. There are other Torx-ish fasteners out there like Ribe and Torx Plus. You should ask from BH what they are using and get a correct bit. Too bad that they do not have a proper maintenance manual.

    You should get a new bolt from BH. The bolt seems to be alloy. I would use a dremel, cut a slit across the head and then use huge flathead screwdriver to get it out.

  22. #22
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    If a manufacturer is using an off size fastener they should include a tool with the bike.
    To drill it out start with a small bit like 3/32 or less.

  23. #23
    EAT MORE GRIME
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    to be safe

    be careful when you drill it out

    it will heat up fast, and heat will ruin the carbon around the
    insert area if it gets too hot. not sure how much that will heatsink on it's
    own but damn if carbon won't delam if it gets hot

    so, drill, but go slow and stop and if it is too hot to
    keep a finger on it, spray bottle and water and keep spraying it
    "Put your seatbelt back on or get out and sit in the middle of that circle of death." - Johnny Scoot

  24. #24
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    Quote Originally Posted by Oh My Sack! View Post
    After all of that, did you at any time try the exact same test you showed in your video with the seat removed completely from the bike, leaving just the post in the seat tube?

    Oh yah thatís the first thing I tried it still creaked like a old boat when I compressed the shock with the seat removed but dropper still inside the frame

  25. #25
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    Quote Originally Posted by noapathy View Post
    I wanna see him hop on the pedals and bounce w/o touching the saddle. If it still creaks, I'd be surprised.
    It does when I stand up on it too or did I should say. I think the seat does make some of the sounds but the majority was from pivot

  26. #26
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    Quote Originally Posted by noapathy View Post
    I wanna see him hop on the pedals and bounce w/o touching the saddle. If it still creaks, I'd be surprised.
    Quote Originally Posted by arnea View Post
    Three sets? Are you saying that the chainstay pivot did not have ball bearings? The big one above bottom bracket in this picture. That would be very strange.

    https://p.vitalmtb.com/photos/users/...jpg?1425655387

    Anyway - you are not supposed to grease the shock pivots.

    https://p.vitalmtb.com/photos/users/...jpg?1425655118

    From this picture it appears that there is Fox 5-piece mounting hardware. If it is too tight you can loosen it up by slightly sanding the outside of the plastic bushings (How to make Fox bushings better), but you should not use any grease. It is also very important to make sure that rotation happens between the plastic bushings and the pin and not between the pin and bolt - later will ruin your rocker.



    It does not look like Torx to me. There are other Torx-ish fasteners out there like Ribe and Torx Plus. You should ask from BH what they are using and get a correct bit. Too bad that they do not have a proper maintenance manual.

    You should get a new bolt from BH. The bolt seems to be alloy. I would use a dremel, cut a slit across the head and then use huge flathead screwdriver to get it out.
    Yeah Iím a little bummed that I assumed this was torx, but I guess itís another lesson learned about assuming.

    I am really surprised that they do not recommend you grease these pivot points on the shock! I guess I just donít really understand how grease can ruin the rocker.

  27. #27
    Self Appointed Judge&Jury
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    I like this internet diagnosis program. Way cheaper than having a bike shop diagnose it.

    Once Apple catches wind of this they'll be charging for the App.
    Quote Originally Posted by mileslong View Post
    I passionately remove rocks and corners and other stuff I find too hard to ride.

  28. #28
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    Quote Originally Posted by Sewer View Post
    I guess I just donít really understand how grease can ruin the rocker.
    Chris from RWC made some helpful pictures. He described something else, but the pictures are good and relevant in general.

    Real World Cycling shock needle bearing kit IS AWESOME - Page 2- Mtbr.com

    The thing that he calls "inner ring" is this shaft with hole where the shock bolt goes through.

    Real World Cycling shock needle bearing kit IS AWESOME - Page 2- Mtbr.com

    If the bolt is not adequately torqued, or there is grease between the "inner ring" and rocker and the bushings are tight, then the "inner ring" will start rotating relative to rocker and wear will happen where the red lines are drawn. Also - when the torque is not correct you might hear some knocks when "inner ring" is moving around, because the bolt has usually little bit smaller diameter than the hole in the "inner ring".

    Real World Cycling shock needle bearing kit IS AWESOME - Page 2- Mtbr.com

    The idea is that the "inner ring" is firmly clamped between the "arms" of the rocker and it is essentially single piece. All the rotation must happen between bushing and the outside of the "inner ring". Bushings are the wear item. And the bushings are designed to work dry. No grease. If the bushings are too tight (that happens a lot) then you have several options: a) don't care - but this will harm the small bump sensitivity b) get a very slightly smaller "inner ring" - Dougal from Shockcraft https://www.shockcraft.co.nz/ can supply them c) if it is Fox 5-piece bushings, sand the outside of bushings as I showed d) get needle bearing kit from RWC that comes with three different "inner rings".

  29. #29
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    Quote Originally Posted by arnea View Post
    Three sets? Are you saying that the chainstay pivot did not have ball bearings? The big one above bottom bracket in this picture. That would be very strange.

    https://p.vitalmtb.com/photos/users/...jpg?1425655387

    Anyway - you are not supposed to grease the shock pivots.

    https://p.vitalmtb.com/photos/users/...jpg?1425655118

    From this picture it appears that there is Fox 5-piece mounting hardware. If it is too tight you can loosen it up by slightly sanding the outside of the plastic bushings (How to make Fox bushings better), but you should not use any grease. It is also very important to make sure that rotation happens between the plastic bushings and the pin and not between the pin and bolt - later will ruin your rocker.



    It does not look like Torx to me. There are other Torx-ish fasteners out there like Ribe and Torx Plus. You should ask from BH what they are using and get a correct bit. Too bad that they do not have a proper maintenance manual.

    You should get a new bolt from BH. The bolt seems to be alloy. I would use a dremel, cut a slit across the head and then use huge flathead screwdriver to get it out.

    Things are screwy with BH right now they are moving shop from Cali to I think Arkansas. The guy that is sending me the bolt from BH is also surprised to find that it isnít torx. I guess whoever is sending me it isnít their normal tech or something. Gotta get to the bottom of this though.

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