Spoke tension advice - FSA vs DT Swiss Tensiometers??

yan_c
yan_c Posts: 81
edited January 2011 in Workshop
Hi, need a bit of advice on spoke tension. Ive got a FSA spoke tensioner http://www.fullspeedahead.com/fly.aspx? ... &taxid=169
and the graphs that come with it are quite obvious. More tension and less deflection.

Now if you download the DT Swiss charts for their spoke range, which is part of the DT swiss tensioner manual, http://www.dtswiss.com/getdoc/ae573d55- ... anual.aspx, this seems to indicate that with increased tension you get increased deflection! I'm pretty sure the tools work in same way, but how come the difference?

Anyone got any ideas on this?
Cheers

Comments

  • Monty Dog
    Monty Dog Posts: 20,614
    Higher tension = reduced deflection
    Make mine an Italian, with Campagnolo on the side..
  • yan_c
    yan_c Posts: 81
    Yes thats what I thought and is how the FSA one works, but according to the DTSwiss charts for their tools and spokes, increased tension means increased deflection!

    They both cant be right can they.

    Bit of confusion here!!

    Cheers
  • LangerDan
    LangerDan Posts: 6,132
    As far as I can make out, the FSA tensiometer measures the deflection of the spoke directly, the DT Swiss tensiometer is measuring the displacement of the handle. The handle's "zero" position corresponds to a completely slack spoke, so the closer the measured value is to zero, the less tension there is in the spoke.

    In the FSA unit, the zero position corresponds to a straight through, fully tensioned spoke (no deflection possible)
    'This week I 'ave been mostly been climbing like Basso - Shirley Basso.'
  • yan_c
    yan_c Posts: 81
    Ok your probably right, but how can I use the DTSwiss spoke tension curves with the FSA tensionmeter, as I use mainly DTSwiss spokes?
    Cheers
  • moonshine
    moonshine Posts: 1,021
    yan_c wrote:
    Ok your probably right, but how can I use the DTSwiss spoke tension curves with the FSA tensionmeter, as I use mainly DTSwiss spokes?
    Cheers

    use a mirror? :wink:

    edit... sorry... not trying to be a smart ar$e.. it might work... :idea:
  • balthazar
    balthazar Posts: 1,565
    Do you need to use a translation graph? The FSA tensiometer reports spoke tension regardless of the spoke thickness, and the ideal tension is determined by the rim manufacturer. Can't you just read the tension from the instrument? What units does it measure in?
  • yan_c
    yan_c Posts: 81
    Aswell as the max rim tension figure, from what I've read you ideally need to be using the spoke at approx 75% of its max tension, ie not too slack but then not too near its max. The FSA tool is in mm with the graph in newtons. Need to find the max rim tension figures for the notubes olympic and podium MMX rims..

    Cheers
  • ride_whenever
    ride_whenever Posts: 13,279
    It's more to do with how strong the rim is.

    You can crank up the tensions evenly and the rim will usually pringle waaaaay before the spokes snap if you're using good quality spokes and brass nipples.


    Personally I really wouldn't worry, just build them straight and even and properly stress relieve them loads.
    Neeermad
    Carbon 456
    456 lefty
    Pompino
    White Inbred
  • yan_c
    yan_c Posts: 81
    Ok thanks. Do you know where I can find the max rim tension figures for the notubes olympic and Podium MMX rims? Notubes dont seem to be much help..

    Cheers
  • balthazar
    balthazar Posts: 1,565
    yan_c wrote:
    Aswell as the max rim tension figure, from what I've read you ideally need to be using the spoke at approx 75% of its max tension, ie not too slack but then not too near its max. The FSA tool is in mm with the graph in newtons. Need to find the max rim tension figures for the notubes olympic and podium MMX rims..

    Cheers

    I think you've received some confused advice. Assuming you're building ordinary wheels with plenty of spokes (>24), the yield point of spokes is much higher than the rim could stand before collapsing into a saddle shape. Consequently, spoke tension is all about the rim.

    If you can't find the specs for your chosen rims, you should use the method detailed in Jobst Brandt's "The Bicycle Wheel". That requires increasing spoke tension evenly, in small increments, until the rim begins to collapse. At that point, back the spoke tension off a small amount, and retrue. Becuase spoke tension only decreases under load, the ideal resting tension is the highest possible, for wheel strength.

    Take that tension reading with your tensiometer, and you have determined the perfect tension for your combination accurately, making any subsequent builds (with the same rims and spoke count) much faster.
  • yan_c
    yan_c Posts: 81
    Ok thanks for that. I'll keep on at notubes as it would be good to have a figure from them for the max rim tension, the must have one!

    Cheers

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