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Thread: Broken Spokes

  1. #1
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    Broken Spokes

    I have a two month old wheel that has broken two spokes, both on the non dished side of the rim. Each time I true the wheel carefully, ensure even spoke tension, ride the bike for a while and it pops another spoke. This really gets old and seems that once a spoke pops on a wheel, the wheel will continue to break them and there is nothing short of getting a new rim and spokes that will fix it. Before I attempt to exchange the wheel, I was wondering if other cyclists on the board agree with the broken spoken domino effect theory.

  2. #2
    Wot no bike? pahearn's Avatar
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    Quote Originally Posted by BikeToWork
    I have a two month old wheel that has broken two spokes, both on the non dished side of the rim. Each time I true the wheel carefully, ensure even spoke tension, ride the bike for a while and it pops another spoke. This really gets old and seems that once a spoke pops on a wheel, the wheel will continue to break them and there is nothing short of getting a new rim and spokes that will fix it. Before I attempt to exchange the wheel, I was wondering if other cyclists on the board agree with the broken spoken domino effect theory.
    Why not just replace the broken spokes instead of getting a new rim/spokes?

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    Classic sign of an undertensioned wheel. Do you also hear pinging noises when you are out of the saddle in small gears? Same thing happened to me, I cranked the tension, problem solved.

    Whats happening is the non drive/non pulling spokes are de-tensioned when you apply torque to the wheel and go completely slack. Repeated cycles make them break.
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    Another alternative is that the tension variation between spokes is too high. I broke a spoke recently. I found a huge variation so I tension equalized the spokes. The process is best done with a tension meter. Should keep the wheel true much longer.

    Al

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    I have a spoke tensionometer but it seems useless for used wheels. If I get the tension equal on all spokes on both sides of the wheel (one side at a time) according to the tensionometer, dishing the wheel so it is centered, then the rim wobbles badly side to side until I true it and mess up the equal tension. I think this is just a really crappy wheel (Performance Terra Topo). It doesn't seem under tensioned based on other wheels I've built and trued. The first time it popped a spoke when I torqued down on the pedals in a low gear to climb a hill. Today it seemed to break when I hit the rear disk brake. Both spokes were on the non-drive side.

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    Broke my first spoke about a month ago.
    I had let the hub lock nuts get loose, eventually it got bad enough to break a spoke (on-drive side) which caused me to flat out. I guess I deserved it for being so lazy about maintenance.
    So after replacing the spoke, check the play on the hub axle, if it feels loose, the hub needs adjusting.

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    OK, several things to address here. First, if if it is truly a new retail wheel you need to return it for a refund. If when the spokes are tensioned evenly the wheel is very out of true then the rim itself is physically bent and defective and the stress of some spokes being way too tight and the flexing from some being too loose certainly could contribute to the breakage.

    Even with those circumstances breaking spokes that much in a short period (assuming your weight is not extremely high) is unusual. I would be very hesitant to reorder the same model of wheel. There are still plenty of instances where wheels are built with poor choices of spoke/hub combinations. If you look at the spoke heads in the hub and there is much room either where they are inserted through the hub (holes too large, spokes too small a guage) or between the actual head and the surface of the hub (flange too thin) you can expect to break spokes.
    Last edited by cny-bikeman; 05-22-07 at 07:16 PM.

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    Klaatu barada nikto cascade168's Avatar
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    BikeToWork, while you are careful to let us know that you have a tensiometer and are using it, there is some basic information that you are not telling us:

    1. How much do you weigh?
    2. How many spokes on the wheel?
    3. What is the max tension the rim is rated for?
    4. What figure (KgF or Nm) are you setting your spoke tension at?

    There are many variables that contribute to broken spokes and there are never definite answers. As others have stated, it's usually undertensioned spokes that cause breaks. Another factor that's very difficult to quantify, but very important, is how you ride the bike. A 140 lb rider that never gets out of the saddle and hits every hole in the road could break a lot of spokes, but, on the other hand, there are plenty of "clydesdale" class riders who are "light" on the pedals and are careful riders that would never break spokes on the same bike as the lightweight rider. You really need to be honest with yourself about this, but my observations are that most riders that are "heavy" on the bike either don't realize what's going on or will not admit it.

    If you are setting all the spokes at the same tension, but it's low (with respect to what the rim will allow), then all that truing and tensioning is for naught. You really need to find out what the rim will take and try hard to get to that figure.

    FWIW, setting tension all around and then truing is not really the way to build a wheel. You should be truing (laterally and radially), dishing, stress relieving, and checking the tension in incremental steps, getting to finer and finer adjustments as you near the final tension. Concentrate on getting the wheel round (radial true) in the early stages and it will make for an easier build. Checking the tension on the non drive side of a rear wheel is really not getting you anything.
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  9. #9
    Faster but still slow slowandsteady's Avatar
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    Though you may be technically correct, I think you guys are missing the point. This is a brand new wheel. It shouldn't require this much effort for a new part to function. He should have been able to put the wheel on and forget about it for a year or two. Send it back for a refund.
    "Ride lots." -- Eddy Merckx

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    Klaatu barada nikto cascade168's Avatar
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    Quote Originally Posted by slowandsteady
    Though you may be technically correct, I think you guys are missing the point. This is a brand new wheel. It shouldn't require this much effort for a new part to function. He should have been able to put the wheel on and forget about it for a year or two. Send it back for a refund.
    I do hear what you are saying, but ...

    I am not accusing BackToWork of being a bad or abusive rider, but I have seen some riders go through brand new wheels like Grant took Richmond, if you catch my drift. Riding style, matching riders to appropriate wheel sets, and other variables, all play into spoke_breaking problems and if you want to come to the correct conclusion as to a root cause, you need to examine them all.

    By all means, get wheels fixed or replaced under warrantee, but if you don't identify the real root cause of the problem (it may not be the wheel), then there is a real chance that you will repeat the failure. It's not always loose spokes or a bad wheel build.
    "Work is the curse of the drinking class."
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    Sheldon Brown says he fixes this problem by respoking the NDS radially. Of course this means changing out half your spokes.

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