Strongest Spokes/Nipples?

Bhima
Bhima Posts: 2,145
edited November 2009 in Road buying advice
Are some aero/bladed spokes stronger than others?

I currently have brass spoke nipples but I see you can buy alloy ones - any difference? (Not bothered about weight at all.)

Comments

  • whyamihere
    whyamihere Posts: 7,708
    Alloy ones are weaker and tend to round off when you're trueing unless you're really, really careful. Alloy nips are purely for light weight or if you're a vain git who wants them anodised a pretty colour.

    In terms of strength, aero spokes are pretty much the same. Double butted are stronger for the weight than plain gauge, and the aero flattening has essentially the same effect as butting the spokes.
  • GavH
    GavH Posts: 933
    Look on wheelbuilders.com, lots of good info about spokes on there including a very interesting weight calculator.
  • balthazar
    balthazar Posts: 1,565
    Spokes in traditional wheels aren't tensioned near their yield point (because the rim would deform first), so strength is not a concern. It is durability that matters with spokes. Double butted spokes are a little more flexible than plain spokes, and this flexibility allows them to support the rim during larger rim deflections, resulting in a stronger wheel.

    Because they have little resistance to torsion, bladed spokes twist very easily during building, which is mightily irritating; however, a consequential benefit is that it is easy to prevent leaving residual twist in spokes from tensioning, because such twist is obvious to see.

    I don't know whether bladed spokes are as flexible, in tension, as butted spokes. I suspect not, because I suspect that tension characteristics are related to spoke cross-section surface area, rather than shape (which dictates their resistance to torsion loads). If I'm right, then they have the characteristics of plain gauge spokes, and a wheel built from them will only be as strong as one built with plain spokes.

    Regardless of wheel strength, any spokes can be made as durable as possible by stress-relieving them.

    Brass is the right material to make spoke nipples from. They won't seize and are strong enough. Aluminium nipples corrode and fail for no benefit.
  • Bhima
    Bhima Posts: 2,145
    Right. Thanks.

    The unbreakable Mavic Cosmic wheels i've been using for the past 14000 kilometers have always stayed true but a spoke actually snapped today at the nipple. :shock: I've suddenly increased my cobble intake in the past few weeks, which left the wheels totally true, but has probably weakened the spokes somehow... This is why I asked. I was wondering if I could make my almost indestructible wheels ever stronger...

    Upon reflection, i'm guessing that the spokes were overtightened? I recently found very loose spokes on the rear which, strangely did not affect the trueness of the wheel, but they seemed dangerously unstable, so I tightened them and the other spokes, to keep the wheel true. I think this lead to overtightening some of them. However, if I left the loose spokes, one more cobbled descent would have killed them, so I think I was in a lose-lose situation...

    :?
  • balthazar
    balthazar Posts: 1,565
    From your first post, I imagined you were talking about traditional wheels with lots of steel wire spokes. The wheels you have are low spoke count design, with proprietary components. I don't think they are considered by Mavic to be modifiable. From looking at pictures, I imagine the ideal spoke tension for such few spokes is so high that it is beyond what you could manage by hand, without some machine compressing the rim radially to prevent nipple binding. However that's a guess as I have no experience of this kind of wheel. Perhaps your LBS could fix it or send it to Mavic.

    Reading the link I gave will still help you understand why spokes fail.
  • Monty Dog
    Monty Dog Posts: 20,614
    Alloy nipples are one of the most useless things ever conceived for a bike - built a pair of Open Pros last winter with DT Revs and the alloy nipples supplied. 3 months later, the alloy nipples start failing due to corrosion under the heads - since replaced with normal brass nipples and haven't touched them since - e.g. rode them on the South Downs Way in the summer on a cross bike. As for Cosmic Carbones - they are strong because they are massively over-built, but doubt you can swap out the spokes and nipples for anything else. I know a pro-team mechanic who won't touch them because he thinks they're so bad.
    Make mine an Italian, with Campagnolo on the side..
  • rake
    rake Posts: 3,204
    i dont know what a service life for a wheel is but 14k seems good. fatigue will get them in the end like constantly bending a paper clip till it breaks. i didnt like the sound of aluminium nipples and after a breakage was supplied with one and it twisted like a pretzel when i installed it. my cheap bike has brass much better. they are so small you would probably save as much weight with a close haircut.
  • Whilst double butted spokes are great, the sapim website have a fatigue test table:

    here

    the cx-rays have a vastly superiour revolution lifetime, but they are also double butted.
  • balthazar
    balthazar Posts: 1,565
    Whilst double butted spokes are great, the sapim website have a fatigue test table:

    here

    the cx-rays have a vastly superiour revolution lifetime, but they are also double butted.
    Hmmm. Perhaps the "Sapim Knowledge Base Lab for Research and Development", in the 28 years it has existed, could have generated a bit more to show for its existence than a nearly unreadably tiny graphic, pitched to sell its most expensive product. They actually embedded this phrase: ".. used by most professional MTB/Road and Racingteams" (sic) on the test data chart...

    This quasi-sciencey marketing guff is mainly frustrating because there actually is something to be done here. Material durability is an interesting subject that has consequences for applications like bike spokes. If Sapim would publish their test procedure, then here may be genuinely useful information, to stand alongside the useful data generated by EFBe, for example.