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  1. #1
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    why do I keep breaking spokes?

    Hi,

    I'm currently cycling through Patagonia, and have broken 10 spokes during the last 2000km. All of them in the back wheel on the left side. 8 of them were the ones that pull when you pedal. My wheels have 32 spokes. Only about 600km were on paved roads, the rest on gravel ranging from bad to very bad.

    The weird thing is that only the ones on the left side break. The drive side are supposed to break more often, right?

    I'm thinking maybe they got damaged when I flew to South America with the bike. In this case, I only have a few more to replace and then they should stop breaking. Or might there be another reason? The wheel has been trued 2 times during the trip and it didn't seem to help.

    Thanks,
    Michal

  2. #2
    Senior Member capejohn's Avatar
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    Max weight for a 32 spoke bike is around 220 lbs. How do you fare with that including gear?
    Bike riding New England gentleman.

  3. #3
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    I think I just fall within the limit, if I add my own weight and the gear I have in the back.

    Thing is - if it was because of excess weight or bad roads, wouldn't the drive side spokes break as well?

  4. #4
    Senior Member blaise_f's Avatar
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    Could be too tight. Could have been traumatized from something in shipping/riding. Hard to say 100%.
    http://bygonebicyclist.com
    Penny-farthing adventures, touring & collecting

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    Where are they breaking? At the elbow, where the spokes cross, elsewhere? What size tires do you have and what pressure do you keep them at?

    It could be that the wheel is undertensioned. NDS spokes have less tension in them to begin with because of the wheel dish, so they might be going slack and getting stressed.

  6. #6
    eternalvoyage
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    Quote Originally Posted by miki150 View Post
    Hi,

    I'm currently cycling through Patagonia, and have broken 10 spokes during the last 2000km. All of them in the back wheel on the left side. 8 of them were the ones that pull when you pedal. My wheels have 32 spokes. Only about 600km were on paved roads, the rest on gravel ranging from bad to very bad.

    The weird thing is that only the ones on the left side break. The drive side are supposed to break more often, right?

    I'm thinking maybe they got damaged when I flew to South America with the bike. In this case, I only have a few more to replace and then they should stop breaking. Or might there be another reason? The wheel has been trued 2 times during the trip and it didn't seem to help.

    Thanks,
    Michal
    Where are the spokes breaking? If at the elbows, that is a sign. If elsewhere, it is another sign. It would help if you could describe or mention where they are breaking.

    Spoke quality is important. DT Swiss spokes are probably the most reliable (of the reasonably priced spokes, at least).

    Spoke diameter is also important.

    Butted spokes are different from straight gauge.

    DT Swiss Alpine III, if you can find them, are one of the best choices for touring.

    It is somewhat counter-intuitive, but loose spokes can be (and often are) stressed much worse than tighter (or properly tensioned) spokes.

    You can try this trick: compromise just a bit on the centering of the wheel, in order to even out the spoke tension (between the drive and non-drive sides), and increase the tension on the non-drive side. I've done this, and it can help. In my experience, it did not affect handling. You could try it and see.

    You can also order rims with offset holes.

    You can cold set your frame to balance the tension as well (along with offsetting the wheel a bit as described above).

    You could increase your spoke count.

    Please keep us posted and let us know what you find.
    Last edited by Niles H.; 04-04-10 at 02:30 PM.

  7. #7
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    The one time I had a problem with repeated spoke breakage was after I hit a rock in the road and damaged the rim. If you've got a damaged rim, you have to replace the rim to stop the spokes from breaking.

  8. #8
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    The spokes break very close to where they bend at the hub. Most of the ones that broke were attached on the inside of the hub. I've looked on the rim, and haven't noticed anything. How can you tell the rim is damaged? Again, if it was damaged wouldn't that affect all the spokes?

    The spokes I have are called Sapim, rustproof, that's all I know. I would have bought a wheel with 36 spokes of better quality, if I had known, but now I have to go with what I've got.

    Could it be the fault of poorly inflated tire?

    So far none of the replacement spokes have broken. Do they normally have some threshold of wear before they break? Or does it mean the original spokes were damaged, and the replacement will last?

  9. #9
    Cycle Year Round CB HI's Avatar
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    Start by rebuilding the wheel with all new DT Swiss spokes. Check the calculation for spoke length (drive side should be about 2 mm shorter) to make sure the length is right for hub and rim. Don't just trust that the current spoke length is right.

    If that does not work, then try some of Niles other suggestions.

    Sometimes, wheels are just poorly built and we never find the reason.

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    Sapim spokes are decent, so I would surprised if it's just a spoke quality issue. My guesses are that either the whole wheel is undertensioned, or the tension is ok but the combination of your load and the terrain is too much for the wheel. NDS (left) spokes can get stressed more than DS spokes because they're under less tension, and therefore can go slack if the wheel takes a hard hit. Do this repeatedly, and eventually the spoke breaks. I don't know if you can get to a good wheelbuilder with a tensiometer in Patagonia, but I would check the spoke tension if possible.

    If you can do it without getting pinch flats, keep your tire pressure low, especially on rough terriain.

  11. #11
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    Quote Originally Posted by miki150 View Post
    The spokes break very close to where they bend at the hub. Most of the ones that broke were attached on the inside of the hub. I've looked on the rim, and haven't noticed anything. How can you tell the rim is damaged? Again, if it was damaged wouldn't that affect all the spokes?

    The spokes I have are called Sapim, rustproof, that's all I know. I would have bought a wheel with 36 spokes of better quality, if I had known, but now I have to go with what I've got.

    Could it be the fault of poorly inflated tire?

    So far none of the replacement spokes have broken. Do they normally have some threshold of wear before they break? Or does it mean the original spokes were damaged, and the replacement will last?
    If the spoke breakage is from fatigue then yes, there is a threshold of wear before they break. Sapim is a respected manufacturer, but they make a variety of products at a variety of prices. If you look at their website, they give the results of their own fatigue testing for each spoke they sell. The cheaper ones definitely don't last as long as the more expensive double butted stainless steel ones.

    If your spokes were too tight (not likely), the wheel would be at risk of collapsing into a potato chip or taco shape. If the spokes are too loose, unevenly tensioned or both the rim would flex more as you rode, and the spoke elbows would fatigue and break.

    Are your spokes butted (thinner in the middle, thicker at each end) or straight gauge? Sometimes you have to pinch the spoke between thumb and forefinger and run your thumb and forefinger up and down the spoke to find the difference. Butted spokes tend to absorb impact better than straight gauge, so they last a lot longer. They also cost more to make, so they tend to be found on much more expensive bicycles, or on expensive handbuilt wheels.

    If the replacement spokes are holding up, keep replacing spokes. When you get some place with a good bike shop, consider having the wheels rebuilt with better spokes. For your next tour, start with properly built wheels with double butted stainless steel spokes (Sapim and DT are both good). Also consider getting a rear wheel with offset spoke holes. These will spread the load more evenly among all the spokes. Wider tires will also help cushion the spokes.

  12. #12
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    that is weird. I wonder if the wheel builder did something funny from day one with the left side spokes, maybe laced it up wrong, bent the spokes then relaced it in another direction. I'd just get a new wheel or complete rebuild with new rim. Start over.

  13. #13
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    Sounds like too little tension. NDS spokes might be un-threading themselves, also due to lack of tension. With not enough tension, the spokes micro-flex at its weakest point, j-bend, fatigue, and break.

    I agree with the above poster. If your wheel was tensioned to high, it would have trouble keeping its trueness, unless a very stiff rim was used.

    I would rebuild the wheel with new spokes & brass nips, tension it evenly, and stress relieve the hell out of it; on high spoke wheels, I walk on the spokes to get all the wind-up out. Use a bit of linseed oil on the threads; it'll set after a day or so and act as a very mild thread-lock.
    Blue Axino

  14. #14
    rhm
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    The issue is spoke tension. If tension is low enough that spokes get a significant reduction in tension at some point in the wheel's revolution, they will fatigue. If you have tightened all your spokes and replaced some, perhaps your new spokes are not getting fatigued, while your old ones continue to break from the fatigue caused previously. If you replace all the old spokes and increase tension to the appropriate level, you will probably have no more trouble; possibly you need to replace them all at some point. Hard to tell.

    While there is such a thing as spoke quality, spoke tension is much much much more important. In most cases a properly tensioned wheel made from cheap spokes will last just as long as a properly tensioned wheel made from expensive spokes.

    Inside spokes, outside spokes... yes, it makes a difference to the way fatigue presents itself; but the problem is still fatigue, and fatigue is what's killing your spokes. The rim may suffer, and may be permanently damaged, on account of the spoke problems; but the rim is not the cause of the problem.

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    I would think if insufficient spoke tension was the issue it would show up predominantly on the right side and not the left, have other folks seen instances where ALL the left side spokes go before the right? That just seems too specific to those spokes to be caused by a universally loose wheel.

  16. #16
    rhm
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    Quote Originally Posted by LeeG View Post
    I would think if insufficient spoke tension was the issue it would show up predominantly on the right side and not the left, have other folks seen instances where ALL the left side spokes go before the right? That just seems too specific to those spokes to be caused by a universally loose wheel.
    Yes, but not necessarily. Since the wheel is dished, the drive side spokes are necessarily going to be under higher tension than the left side spokes. Whether the drive side spokes are properly tensioned, or are suffering metal fatigue as well, I can't speculate; but evidently they are not yet fatigued to the breaking point (which is a good sign).

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    NDS tension is less much, due to dish. Those spokes will go slack much easier, thus they brake first.

    The failure is probably from not having enough tension on DS spokes, which results in under-tensioned NDS spokes. Though, without seeing the wheel, is just a speculation. My first few rear wheels I built failed on NDS side from lack of tension.
    Blue Axino

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    Quote Originally Posted by capejohn View Post
    Max weight for a 32 spoke bike is around 220 lbs. How do you fare with that including gear?
    I weigh 275 and my 36 spoke bike hasnt broke a spoke yet.

  19. #19
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    Once you start breaking spokes, there can be a zipper effect- because you rode some amount with a broken spoke, the spokes around it have assumed extra load and may have been overstressed. The next time you hammer up a hill or hit a bump the wrong way, one of those spokes pop, stressing the spokes around it. I had a wheel that started doing that and after the LBS fixed one or two they showed me how to fix the spokes and let me do them myself. I started marking the spokes that broke and, just as you observed, they were all in a row on the same part of the wheel. (This was on a 36-spoke wheel. I weigh 220 and was carrying maybe 30 lb. of commuting junk.)
    I stop for people / whose right of way I honor / but not for no one.



    Originally Posted by bragi "However, it's never a good idea to overgeneralize."

  20. #20
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    Quote Originally Posted by Doohickie View Post
    I started marking the spokes that broke and, just as you observed, they were all in a row on the same part of the wheel. (This was on a 36-spoke wheel. I weigh 220 and was carrying maybe 30 lb. of commuting junk.)
    did yours all go on the left or right side?

  21. #21
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    Quote Originally Posted by availpunk9 View Post
    NDS tension is less much, due to dish. Those spokes will go slack much easier, thus they brake first.

    .
    except most folks experience spoke breakage on the drive side

  22. #22
    rhm
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    Quote Originally Posted by LeeG View Post
    except most folks experience spoke breakage on the drive side
    Are you sure about that? I don't think I've seen any statistics on the matter.

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    Quote Originally Posted by rhm View Post
    Are you sure about that? I don't think I've seen any statistics on the matter.
    I recall a survey on this forum or another that listed most common mechanical failures and I think drive side spoke breakage was the most common . I don't doubt that something caused all the spokes to break on one side but my limited experience is that most breakages are rear drive side.

  24. #24
    You gonna eat that? Doohickie's Avatar
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    Quote Originally Posted by LeeG View Post
    did yours all go on the left or right side?
    Drive side.... right.
    I stop for people / whose right of way I honor / but not for no one.



    Originally Posted by bragi "However, it's never a good idea to overgeneralize."

  25. #25
    rhm
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    Quote Originally Posted by LeeG View Post
    I recall a survey on this forum or another that listed most common mechanical failures and I think drive side spoke breakage was the most common . I don't doubt that something caused all the spokes to break on one side but my limited experience is that most breakages are rear drive side.
    Hmmm, yeah, well, okay. I dunno.

    Spokes may break for more than one reason. What OP described, I maintain, is from insufficient tension on the spokes --either the left side spokes or all, I can't tell yet. That's different from the zipper effect, described by Doohickie a couple posts back, which is what happens when one spoke fails and the ones next to it come under increased tension. The zipper effect may be happening with spokes that are already compromised by fatigue. Aside from that, you can take a brand new wheel, perfectly tensioned, and hit a bump hard enough to break a spoke.


    As for the drive side, versus non-drive side; the drive side spokes are typically under more tension, on account of the wheel's dished shape. In some circumstances this may make a difference to spoke longevity. It's hard to troubleshoot the problem in the abstract.
    Last edited by rhm; 04-06-10 at 05:57 AM. Reason: typo!

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