Different left-right spoke tension?

Discussion in 'Bicycle Mechanics and Repairs' started by Membrane, 4 Oct 2007.

  1. Membrane

    Membrane New Member

    Just to satisfy my curiosity: rear wheel spokes on the drive side have a higher spoke tension, do the spokes on one side not balance out the tension on the other side?

    I presume that the reason for the higher tension is to reduce the flex when driving the wheel and thus reduce energy loss, but why is it that the spokes on the non drive side are wound to a lower tension?

    Aside: I presume that on a fixie with a flippable rear wheel (fixed - freewheel) the spoke tension on both sides is high?
     
  2. bonj2

    bonj2 Guest

    I may be wrong but as far as I was aware there should be no difference between the tension in spokes from one side to the other. If the wheel needs to be dished, then one side will have slightly shorter spokes to effect this, not have more tension.
    When you're pedalling, then the trailing spokes will have more tension in them than the leading spokes, and under disk braking then the leading spokes will have more tension. However in both situations this increased tension is due to the hub trying to apply a torque (rotational force) to the rim through the spokes, the fact that the driveside is on one side of the hub doesn't mean this side takes most of the tension.
     
  3. Arch

    Arch Married to Night Train

    Location:
    Salford, UK
    No, as far as I know, spoke tension shouldn't differ. All spokes, when pinged, should sound the same... Will have to test this when I get home...
     
  4. twowheelsgood

    twowheelsgood Senior Member

    Location:
    Zurich Switzerland
    According to spocalc, for shimano hubs with open pro rims, the tension R/L should be 48%.
     
  5. If it were a radially-laced rim, spoke tension on the two sides would be equal, but it's cross-laced and with dish so you have greater tension in the drive side than non-drive.

    Peter White custom wheelbuilding :-
    http://www.peterwhitecycles.com/Wheels.asp
    Real-Design wheels FAQ's :-
    http://www.real-design.com/2005/faq.aspx
     
  6. barq

    barq Senior Member

    Location:
    Birmingham, UK
    Andy is right, spoke tension should be even between spokes on the same side, but dished wheels have significantly different tension tension between sides. This means that in the truing process adjustments on the drive side spokes make much more difference - so half a turn of a spoke key one side doesn't equal half a turn on the other.

    Not sure I agree with the Real-Design wheels FAQ: If the wheel is built with correct spoke tension and stress-relieved then the spokes shouldn't come loose and the wheel shouldn't need a breaking in period. But they are right about the asymmetric spoke tension being a weak point, which is why wheels for downhill bikes are built dishless as it makes them much stronger.
     
  7. Sort-of. Like the Peter White quote says, if the rim were exactly true, then all the spokes on the same side would be equally-tensioned. But if the rim isn't quite round, then in truing it up you'd end-up with slightly different tensions.
     
    Ajax Bay likes this.
  8. barq

    barq Senior Member

    Location:
    Birmingham, UK
    Yeah, emphasis very much on the word 'should'. Obviously I'm describing the ideal. But unless a rim is quite far gone, you can normally get the spoke tension pretty even.

    I have to confess to having become quite obsessed with it since I got a tensiometer. I have a spreadsheet of spoke tension for each wheel which is shockingly anal! :biggrin:
     
  9. AcademicX

    AcademicX New Member

    Location:
    East Yorkshire
    A drive side spoke on the rear wheel of my Campag Neutron Ultra's let go on Sunday and the effect was frightening. Once I got back I had a look at the manual only to discover that the recommended tension for the drive side is 130-150kg as opposed to 60-80kg for the non-drive side. That difference accounts for the major buckle in the wheel (and the loss of a nearly-new Schwalbe Ultremo tyre)[:biggrin:]

    So, yes, there is a difference in spoke tension on some wheels [:biggrin:]
     
  10. unigeezer

    unigeezer Active Member

    Because of the difference in tension between disc and non disc side, would that result in a greater likelihood of broken spokes?
     
  11. PapaZita

    PapaZita Veteran

    Location:
    St. Albans
    Ooh, old thread! :smile:

    Yes, it can do, but not always in the way that people expect. Normal load on a wheel reduces the tension in the spokes. If the load is so large that the tension in a spoke goes all the way to zero, not only does the spoke stop supporting the wheel, but it is also at particular risk of fatigue failure. Because they have less tension to begin with, it is the non-drive side spokes (of a rear wheel) that are most prone to fail in this way. The ratio between the tensions of the drive and non-drive side spokes is fixed by the geometry of the wheel (the amount of dish). One of the considerations when designing a wheel is how to achieve sufficient tension in the non-drive spokes for a strong wheel, without the tension of the drive side being too high for the rim.
     
    Smokin Joe likes this.
  12. Ajax Bay

    Ajax Bay Veteran

    Location:
    East Devon
    Very old thread.
    The spokes on one side [DO] "balance out the tension" [from the spokes on] the other side.
    The tension difference is not to do with wheel flexing or energy loss.
    "Why is it that the spokes on the non drive side are wound to a lower tension?"
    Because (on a normal rear wheel) the drive side spokes arrive at the rim at a shallower angle, because of the dishing necessary to make room for the sprockets. If one 'resolves' the force exerted by each spoke at the rim, the lateral element of that force are equal and opposite (so they "balance out"). I have read that typical tensions are 1400N on the drive side and 1000N on the non-drive side.
    With a flippable rear wheel, there is no dishing, because the distance from the locknut to the sprocket is the same both sides. The mean tension in the spokes on both sides, as in a front wheel, will therefore be more or less the same.
    HTH
     
    Last edited: 14 Dec 2018 at 18:11
    PapaZita likes this.
  13. YukonBoy

    YukonBoy Guru

    Location:
    Mars
    There is less dishing involved in a disc rear wheel.
     
  14. Is 11 year old thread resurrection a record?
     
  15. Smokin Joe

    Smokin Joe Legendary Member

    Some names on here who have long since disappeared.
     
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