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Wheel build and spoke breaking...

sewerynseweryn Posts: 49
edited March 2015 in Workshop
Hi Guys,

My Friend has a small problem with his own wheel that he built himself. The front wheel is laced radially with 20 nr CX-Ray spokes on Hope Pro3 Hub and with Stans 340 rim. The rider weight is only 72-75kg, however the spokes break at the hub / J-bend section during off saddle efforts. The tension between spokes is within 10-15% uniformity.

My theory and the way I would fix the problem would be to change the spoke type for a more flexible spoke or lacing pattern to 1 or 2-cross, or both. Also, the spoke washers may be a good idea here. However, I will appreciate your comments and help on this.

Posts

  • Smokin JoeSmokin Joe Posts: 2,706
    Spokes work in tension so the way the wheel is laced would have no bearing on the load on the spokes. I've never used a tension meter so I don't know how close a tolerance you need between spokes but 15% does sound like a lot.
  • dgunthordgunthor Posts: 644
    crossed spokes will be a lot stronger, radial looks nice but in reality crossed is better
  • brettjmccbrettjmcc Posts: 1,361
    He's breaking spokes on the front?

    My understanding was that you should have tensions equal, not within 10-15%. If you built the front to 100kgf, then 15% would mean one spoke potentially at 85kgf. How have you determined

    a/ the variance
    b/ you are measuring the tension properly
    BMC GF01
    Quintana Roo Cd01
    Project High End Hack
    Cannondale Synapse SL (gone)
    I like Carbon
  • trailflowtrailflow Posts: 1,311
    Spokes too short ?
  • Smokin JoeSmokin Joe Posts: 2,706
    dgunthor wrote:
    crossed spokes will be a lot stronger, radial looks nice but in reality crossed is better
    No they won't. As I said above, whether spokes are crossed or not makes no difference to the load they have to bear.
  • sewerynseweryn Posts: 49
    Thank you for all responses. I will update if we find the solution for the problem finally.
  • ugo.santaluciaugo.santalucia Posts: 26,443
    Measuring exact tension in CX Ray is not that easy as they fall in the high deflection zone (low reading) in pretty much all meters. You need a good calibration to get a reasonably accurate value...
  • sewerynseweryn Posts: 49
    Measuring exact tension in CX Ray is not that easy as they fall in the high deflection zone (low reading) in pretty much all meters. You need a good calibration to get a reasonably accurate value...
    Thanks Ugo. The tension meter used is the Park Tool TM-1. I believe changing the spoke type should help making the wheel reliable? Or how to make it unbreakable is the question...
  • brettjmccbrettjmcc Posts: 1,361
    The TM-1 will read low. I copied hypster's design and built myself a calibration meter. I still question why you have so much variation in the spoke tension though
    BMC GF01
    Quintana Roo Cd01
    Project High End Hack
    Cannondale Synapse SL (gone)
    I like Carbon
  • ugo.santaluciaugo.santalucia Posts: 26,443
    brettjmcc wrote:
    . I still question why you have so much variation in the spoke tension though

    There is no need for willy waving, a total variation of 15% is perfectly fine and normal if that means the lowest is 85 and the highest is 100 and on average they are somewhere in the 90s.

    If that means the lowest is 85 and the highest is 115 then it is a different story, but that's not 15%
  • dgunthordgunthor Posts: 644
    Smokin Joe wrote:
    dgunthor wrote:
    crossed spokes will be a lot stronger, radial looks nice but in reality crossed is better
    No they won't. As I said above, whether spokes are crossed or not makes no difference to the load they have to bear.

    have to disagree with you as i had a 28 hole radial front which went out of true easily, relaced in 2 crossed and no issues. crossed means the spokes support eachother surely, similar to crossmembers in scaffolding
  • apreadingapreading Posts: 4,533
    I think crossed spreads the load over more spokes, whereas radial has just a single spoke under peak pressure.
  • Smokin JoeSmokin Joe Posts: 2,706
    apreading wrote:
    I think crossed spreads the load over more spokes, whereas radial has just a single spoke under peak pressure.

    How?

    Spokes work ONLY in tension. Think about it.
  • Smokin JoeSmokin Joe Posts: 2,706
    dgunthor wrote:
    Smokin Joe wrote:
    dgunthor wrote:
    crossed spokes will be a lot stronger, radial looks nice but in reality crossed is better
    No they won't. As I said above, whether spokes are crossed or not makes no difference to the load they have to bear.

    have to disagree with you as i had a 28 hole radial front which went out of true easily, relaced in 2 crossed and no issues. crossed means the spokes support eachother surely, similar to crossmembers in scaffolding

    No they do not. As for your radial going out of true that was down to poor build quality. I spent five years up to recently riding a self built 28 spoke radial and it never missed a beat.
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