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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:
    York, 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.
     
  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:]