Chainstay Gusset: Good design or band-aid?- Mtbr.com
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  1. #1
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    Chainstay Gusset: Good design or band-aid?

    I cracked the chainstay on my custom 29er frame. This is the 3rd frame I've broken in this spot, but honestly I wasn't expecting to have a problem with a custom frame.

    The frame builder has agreed to fix it for a small fee but I'm worried his solution is insufficient or just putting a band-aid on a normal chainstay instead of beefing things up and using a stronger chainstay, or a forged yoke, or whatever.

    I've explained to him that I'm a strong rider, and that this bike is SS, and that I've broken multiple frames in the past (5), but I'm not sure if he is taking me seriously enough?

    In your opinion is this a good design or a bad idea? My current frame does not have the brace between the stays either.


    Chainstay Gusset: Good design or band-aid?-gusset-1.jpg

    Chainstay Gusset: Good design or band-aid?-gusset-2.jpg

    The broken frames

    Chainstay Gusset: Good design or band-aid?-img_8221.jpg

    Chainstay Gusset: Good design or band-aid?-img_8224.jpg

    Chainstay Gusset: Good design or band-aid?-img_7946.jpg
    Rigid SS 29er
    SS 29+
    Fat Lefty
    SS cyclocross
    Full Sus 29er (Yuck)

    Stop asking how much it weighs and just go ride it.

  2. #2
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    It's probably worth a shot. Might work fine. Why are they charging you for the repair? Out of warranty at this point?

    As long as the builder makes it clear they will fully warranty it if the repair doesn't work, I'd say go for it.

    I'd guess that the reason the builder doesn't want to replace the stay is that fillet brazed stuff is a HUGE pain to do that with. Removing all that brass sucks. It's a bummer to have to fix something you built (trust me, I know) but you should probably insist that the builder will stand behind the repair, regardless of how it's done.

    -Walt

  3. #3
    pvd
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    Stop buying bikes from terrible builders. You're not braking bikes because you're so "strong", you're breaking bikes because they are built like garbage.

  4. #4
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    From somebody else with a long history of breaking bikes in the exact same spot; Out of curiosity, do you kick the bike out right on jumps? I toned it down on landing whips still sideways, and I haven't broken any more chainstays.

  5. #5
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    Every gusseted frame i've broken cracked at the end of a gusset. That's how the only chainstay i've cracked went. I'm not a fan. Also not an authority.

    No chainstay brace is no big deal, and the one you took pictures of looks like a can opener.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  6. #6
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    I hate to armchair advise but I'll be nicer than PVD at least. I would say it's worth a try too but looks like he's still using the same chainstay. We don't know what wall thickness it is and who makes it and how much he smoothed the fillet there and could've undercut the tube at the transition from brass to steel. Assuming those are all taken care of, straight gauge round tubing and a Paragon yoke would be my solution for a singlespeeder like yourself. I've had a chainstay crack there but it was due to a scallop i brazed in for chainring clearance. Meaning that any added complexity sometimes can cause the problem rather than fix it. Being a rear triangle, is there flex in the whole rear end that is contributing too? What seatstays and dropouts are being used? There are also tandem chainstays that are over 1mm wall thickness that could be used in case those are 0.9mm or under.

  7. #7
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    Thanks for the responses. Sorry for any confusion, I'll clear up a couple details.

    - The chainstay is being completely replaced, then reinforced with the gussets. He first told me the chainstay he wanted to use was out of stock, then sent me the two pictures of the reinforced setup. (that is not my bike, only an example of what he is proposing for the repair).

    - The frame is less than 2 years old and only see's seasonal use, it hasn't seen that much ride time considering I have 7-8 other bikes too, but it is my primary summer bike. I'm paying for the repair because when the frame originally arrived it was warped and the rear hub spacing was off. I had to have it cold set locally and I got a partial refund from the frame builder. Long story but I opted for the partial refund and just figured we would go our separate ways. If I paid full price I would expect some kind of warranty but as it worked out I was willing to accept that my partial refund negated that. He also gave me a very reasonable price for the repair compared to other quotes I got from local frame builders I contacted first. They urged me to contact the original frame builder. (The frame was also not what I asked for in two other aspects. I specifically asked for clearance for a 2.4 tire and my 2.35 Forekaster hits the seat tube severely making the front portion of my swingers completely useless unless I run a smaller tire. That and the reach is not what I asked for. I wanted to run a shorter stem but ended up back at 80mm.)

    - This bike has only ever been setup with a carbon rigid fork and SS. No big jumps, drops, or abusive behavior. Don't get me wrong I ride hard, and I love climbing, but this is not the bike for whips, tricks, or rowdy riding. I don't think I'm superhuman but a pattern is forming and drive side chainstays are clearly taking a lot of abuse. I broke my Surly Wednesday frame this winter in the same place, warranty guy said that's the first time he's seen that. Again a seasonal bike and limited ride time. The other one I broke was my first SS, a Kona Unit. Broke the chainstay in two places, crack at the yoke and broken clean through by the dropout. I didn't post pics of that one. For the record I'm 6'3" 205lbs and pretty avid rider, cat 1 racer.

    - there's no chance it was undercut, the fillet brazing is unfinished by request. I liked the industrial look that showed the craftsmanship.

    I couldn't tell you what chainstay was used originally, only that I requested TT OX Platinum on the front triangle. The dropouts are Paragon Swingers.

    I'm sure a couple of you frame builders cringe as you read this, looking back it wasn't a great experience. At the time I was on a tight budget and he was one of the most affordable options I could find. Communication has been the most challenging part, I really wish he would return an e-mail or phone call. I didn't come here to drag his name through the mud though, I'm in it now and I just want my bike back on the trail. I just don't want to go through this again and was wondering if this seems like a valid repair.

    Seems like nobody strongly objects with the concept of the brace and gussets. Of course there's more than one way to skin a cat but if this will make for a reliable, long lasting repair I'm good with it.

    Thank you all for your input.
    Rigid SS 29er
    SS 29+
    Fat Lefty
    SS cyclocross
    Full Sus 29er (Yuck)

    Stop asking how much it weighs and just go ride it.

  8. #8
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    Based on breaking the same place on a Surly and Kona I think itís safe to say itís you, not the builder, chainstay, design, etc. but that doesnít mean it canít be fixed right.

    If I were you the next frame Iíd buy would be from a builder or company that will warranty the frame (and build what you asked for). Were that my frame i would fix it for free and make it bombproof.

    As far as that fix I personally wouldnít use plate for a bridge and use a tube instead, and Iíd use tandem chainstays or thick wall straight gauge tubing for the chainstays (1.2mm/0.049Ē wall).




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  9. #9
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    I use gussets and have found that they are a good solution, but, you will never fully know until you try. It could then break after the end of the gusset. Agree with Meriwether, use a tandem Chainstay, Gusset with a taper rather than a squared off end, use a round brace.

    Chainstays off the BB are really no different than forks, and forks off bikes from earlier decades often had gussets. There are reasons why this happened. Applying the same approach is sound.

    Eric
    If I don't make an attempt, how will I know if it will work?

  10. #10
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    It sounds like this is someone (the builder, that is) who is VERY new to building frames and/or had a bad day when they built yours. That's the nicest way I can put it...

    Honestly given the other problems with the frame, I might just cut my losses and start over. Even if the builder promises to warranty their work going forward, I wouldn't have a ton of faith in it based on what you've told us.

    Good luck!

    -Walt

  11. #11
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    Quote Originally Posted by Walt View Post
    It sounds like this is someone (the builder, that is) who is VERY new to building frames and/or had a bad day when they built yours. That's the nicest way I can put it...
    Nope, 30 years of experience.
    Rigid SS 29er
    SS 29+
    Fat Lefty
    SS cyclocross
    Full Sus 29er (Yuck)

    Stop asking how much it weighs and just go ride it.

  12. #12
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    lemme get this straight

    -30 year veteran
    -frame arrived bent
    -no more warranty cuz you had to get it fixed
    -inadequate tire clearance
    -wrong front triangle geometry
    -cracked very early in ownership
    -doesn't respond to calls or email


    You're being VERY charitable here. I'm impressed; i doubt i'd have the same restraint. I'd give the repair a go, but i'd also be prepared to cut my losses.



    Don't use plate for braces.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  13. #13
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    Quote Originally Posted by *OneSpeed* View Post
    Nope, 30 years of experience.
    OP has requested no more "outing" of the builder here.

    Feel free to continue to discuss the proposed repair if you're interested in that portion of the discussion.

    -Walt
    Last edited by Walt; 05-19-2019 at 03:48 PM.

  14. #14
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    Quote Originally Posted by Meriwether View Post
    Based on breaking the same place on a Surly and Kona I think itís safe to say itís you, not the builder, chainstay, design, etc. but that doesnít mean it canít be fixed right.
    Maybe...

    ...but maybe One Speed is one of those riders who simply won't ride anything but a threaded 73mm bottom-bracket shell (or, based on the number of shims behind his BB cup, is that a 68mm shell?). In which case, his component preferences are constraining him to frames where the chainstays are over-leveraged by their narrow position where attached to a narrow BB shell. That's a design issue in that he's choosing a design that is inherently too weak for the type of riding he is doing. So, how about using a wider BB86 bottom bracket shell and attaching the chainstays further apart to reduce the leverage on that joint?

  15. #15
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    Quote Originally Posted by VegasSingleSpeed View Post
    Maybe...

    ...but maybe One Speed is one of those riders who simply won't ride anything but a threaded 73mm bottom-bracket shell (or, based on the number of shims behind his BB cup, is that a 68mm shell?). In which case, his component preferences are constraining him to frames where the chainstays are over-leveraged by their narrow position where attached to a narrow BB shell. That's a design issue in that he's choosing a design that is inherently too weak for the type of riding he is doing. So, how about using a wider BB86 bottom bracket shell and attaching the chainstays further apart to reduce the leverage on that joint?
    That's the first i've ever heard of BB shell width impacting chainstay durability. I'm having trouble picturing why it would make a noteworthy difference, aside from possibly requiring less chainstay manipulation.

    I assume he's breaking frames by tipping the bike while standing...?
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  16. #16
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    Quote Originally Posted by scottzg View Post
    That's the first i've ever heard of BB shell width impacting chainstay durability. I'm having trouble picturing why it would make a noteworthy difference, aside from possibly requiring less chainstay manipulation.
    If you move the attachment of the chainstays to the BB apart, you will reduce the forces on the chainstays caused by lateral deflection of the BB (such as during pedaling out of the saddle). I thought it was fairly well understood that doing this increases lateral stiffness...so, why is that? Because the same materials are exposed to less stress, and therefore experience less strain. It's simply moment-arm length and physics.

    The position of his chainstays where they attach to the BB shell is further narrowed by the builder to allow enough space for those large fillets.


    Anyway, I'm throwing the idea out there because a different design will change the stresses at the BB/chainstay. His builder isn't changing the design nor the stresses...he's simply adding more material. At 205 lbs and a Cat 1 cyclist, I think One Speed is putting down some serious power, and on a single-speed that is going to produce significant force at the BB/chainstays.

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