Proper tension for Rolf Sestriere?

Discussion in 'Cycling Equipment' started by Matt O'Toole, Oct 27, 2003.

Thread Status:
Not open for further replies.
  1. Matt O'Toole

    Matt O'Toole Guest

    I have some Rolf Sestriere Ti wheels, which are practically brand new. They aren't even as tight as
    some conventional wheels I've had. So I'm wondering what the proper tension should be. I want to
    make sure they're perfectly tuned before I ride on 'em and bend 'em up. Any thoughts?

    These are spoked 20f, 24r. The rims are similar to other contemporary, semi-aero designs. The spokes
    are paired, but round/conventional, not bladed.

    Any thoughts?

    Matt O.

    PS -- I probably *will* unload these in favor of something more reliable, but I want to bring these
    up to par while I still have 'em.
     
    Tags:


  2. Jim Beam

    Jim Beam Guest

    > I have some Rolf Sestriere Ti wheels, which are practically brand new. They aren't even as tight
    > as some conventional wheels I've had. So I'm wondering what the proper tension should be. I want
    > to make sure they're perfectly tuned before I ride on 'em and bend 'em up. Any thoughts?

    matt

    if the spokes are ti, they're unlikely to feel as "tight" as steel spokes, and increased tension is
    not going to do anything to change it. ti has about half the modulus of steel, so, very roughly
    speaking, a 14-gauge ti spoke is going to be twice as elastic as a 14-gauge steel one.

    other than that, just make sure they're properly tensioned in the normal way. sorry!
     
  3. Dianne_1234

    Dianne_1234 Guest

    "Matt O'Toole" <[email protected]> wrote in message
    news:<[email protected]>...
    > I have some Rolf Sestriere Ti wheels, which are practically brand new. They aren't even as tight
    > as some conventional wheels I've had. So I'm wondering what the proper tension should be.

    Those are limited by the use of Revolution spokes on the drive side, and by the rear hub's high
    dish. You pretty much tighten the spokes until the first right side spoke yeilds (combined tension
    and torsion), and that's your limit.

    They are probably at the limit now. The ones I've seen never get the spokes very tight. Just ride
    and enjoy!
     
  4. Carl Fogel

    Carl Fogel Guest

    jim beam <[email protected]> wrote in message news:<[email protected]>...
    > > I have some Rolf Sestriere Ti wheels, which are practically brand new. They aren't even as tight
    > > as some conventional wheels I've had. So I'm wondering what the proper tension should be. I want
    > > to make sure they're perfectly tuned before I ride on 'em and bend 'em up. Any thoughts?
    >
    > matt
    >
    > if the spokes are ti, they're unlikely to feel as "tight" as steel spokes, and increased tension
    > is not going to do anything to change it. ti has about half the modulus of steel, so, very roughly
    > speaking, a 14-gauge ti spoke is going to be twice as elastic as a 14-gauge steel one.
    >
    > other than that, just make sure they're properly tensioned in the normal way. sorry!

    Dear Jim,

    Forgive the anguished cry of the layman, but what do you mean? I'm not teasing you or being
    sarcastic, just trying to understand what you wheel-builders are saying. It may be like trying to
    understand baseball batters.

    Titanium spokes won't feel as tight as steel, so other than that make sure that they're properly
    tensioned in the normal way?

    I'm guessing that this means that "feel" isn't what you consider the proper, normal method of
    tensioning spokes, but I'm not sure that I'm right.

    Still confused,

    Carl Fogel
     
  5. Jim Beam

    Jim Beam Guest

    > Titanium spokes won't feel as tight as steel, so other than that make sure that they're properly
    > tensioned in the normal way?

    if you have two springs, one rated at 20lbs & the other at 10lbs, the 20lb spring is going to
    deflect half that of the 10lb spring for each lb of load. a ti spoke has roughly half the modulus of
    an identically sized steel spoke so is roughly twice as elastic.

    > I'm guessing that this means that "feel" isn't what you consider the proper, normal method of
    > tensioning spokes, but I'm not sure that I'm right.

    it's nothing to do with tensioning method. it's purely a function of the modulus. easy!
     
  6. matt-<< I have some Rolf Sestriere Ti wheels, which are practically brand new. They aren't even as
    tight as some conventional wheels I've had. So I'm wondering what the proper tension should be.
    >><BR><BR>

    To really be sure, have a tensionometer slapped on them, with a proper look at the tension
    conversion chart. Your idea to ensure they are built correctly, with these and ohhh so many other
    wheels outta boxes, is a good one before you ride them.

    Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
    (303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"
     
  7. Dave Lehnen

    Dave Lehnen Guest

    jim beam wrote:
    >> Titanium spokes won't feel as tight as steel, so other than that make sure that they're properly
    >> tensioned in the normal way?
    >
    >
    > if you have two springs, one rated at 20lbs & the other at 10lbs, the 20lb spring is going to
    > deflect half that of the 10lb spring for each lb of load. a ti spoke has roughly half the modulus
    > of an identically sized steel spoke so is roughly twice as elastic.
    >
    >> I'm guessing that this means that "feel" isn't what you consider the proper, normal method of
    >> tensioning spokes, but I'm not sure that I'm right.
    >
    >
    > it's nothing to do with tensioning method. it's purely a function of the modulus. easy!
    >

    The force you feel when deflecting a tensioned spoke is not purely or even primarily a function of
    modulus. It would be for a spoke with zero initial tension, but not for a tensioned spoke. At small
    deflections the additional elongation is negligible, and the resisting force comes from the sines of
    the deflection angles and the initial tension. At high deflections, additional elongation becomes
    significant and modulus does matter.

    Dave Lehnen
     
  8. Carl Fogel

    Carl Fogel Guest

    Dave Lehnen <[email protected]> wrote in message
    news:<[email protected]>...
    > jim beam wrote:
    > >> Titanium spokes won't feel as tight as steel, so other than that make sure that they're
    > >> properly tensioned in the normal way?
    > >
    > >
    > > if you have two springs, one rated at 20lbs & the other at 10lbs, the 20lb spring is going to
    > > deflect half that of the 10lb spring for each lb of load. a ti spoke has roughly half the
    > > modulus of an identically sized steel spoke so is roughly twice as elastic.
    > >
    > >> I'm guessing that this means that "feel" isn't what you consider the proper, normal method of
    > >> tensioning spokes, but I'm not sure that I'm right.
    > >
    > >
    > > it's nothing to do with tensioning method. it's purely a function of the modulus. easy!
    > >
    >
    > The force you feel when deflecting a tensioned spoke is not purely or even primarily a function of
    > modulus. It would be for a spoke with zero initial tension, but not for a tensioned spoke. At
    > small deflections the additional elongation is negligible, and the resisting force comes from the
    > sines of the deflection angles and the initial tension. At high deflections, additional elongation
    > becomes significant and modulus does matter.
    >
    > Dave Lehnen

    Dear Dave,

    I suspect that what you're saying is said quite clearly for the engineering crowd, but I'm so far
    behind here that I'm not even certain that I'm on the same page as you and Jim.

    By "deflecting" do you mean plucking or pushing the tensioned spoke sideways to get a "feel" for the
    "tightness," a sort of seat-of-the-pants tension-measurement that a tensiometer would measure far
    more slowly and accurately?

    If so, are you and Jim discussing whether this sideways "feel" would be noticeably different between
    steel and titanium spokes, given the small sideways movement involved, with Jim suggesting that the
    twice-as-elastic titanium spoke would bend or deflect further, while you suggest that the elastic
    difference doesn't actually matter much for a tensioned spoke that moves only slightly sideways?

    Sorry if I've completely missed what's being said.

    Carl Fogel
     
  9. Dave Lehnen

    Dave Lehnen Guest

    Carl Fogel wrote:

    > Dave Lehnen <[email protected]> wrote in message
    > news:<[email protected]>...
    >
    >>jim beam wrote:
    >>
    >>>>Titanium spokes won't feel as tight as steel, so other than that make sure that they're properly
    >>>>tensioned in the normal way?
    >>>
    >>>
    >>>if you have two springs, one rated at 20lbs & the other at 10lbs, the 20lb spring is going to
    >>>deflect half that of the 10lb spring for each lb of load. a ti spoke has roughly half the modulus
    >>>of an identically sized steel spoke so is roughly twice as elastic.
    >>>
    >>>
    >>>>I'm guessing that this means that "feel" isn't what you consider the proper, normal method of
    >>>>tensioning spokes, but I'm not sure that I'm right.
    >>>
    >>>
    >>>it's nothing to do with tensioning method. it's purely a function of the modulus. easy!
    >>>
    >>
    >>The force you feel when deflecting a tensioned spoke is not purely or even primarily a function of
    >>modulus. It would be for a spoke with zero initial tension, but not for a tensioned spoke. At
    >>small deflections the additional elongation is negligible, and the resisting force comes from the
    >>sines of the deflection angles and the initial tension. At high deflections, additional elongation
    >>becomes significant and modulus does matter.
    >>
    >>Dave Lehnen
    >
    >
    > Dear Dave,
    >
    > I suspect that what you're saying is said quite clearly for the engineering crowd, but I'm so far
    > behind here that I'm not even certain that I'm on the same page as you and Jim.
    >
    > By "deflecting" do you mean plucking or pushing the tensioned spoke sideways to get a "feel" for
    > the "tightness," a sort of seat-of-the-pants tension-measurement that a tensiometer would measure
    > far more slowly and accurately?
    >
    > If so, are you and Jim discussing whether this sideways "feel" would be noticeably different
    > between steel and titanium spokes, given the small sideways movement involved, with Jim suggesting
    > that the twice-as-elastic titanium spoke would bend or deflect further, while you suggest that the
    > elastic difference doesn't actually matter much for a tensioned spoke that moves only slightly
    > sideways?
    >
    > Sorry if I've completely missed what's being said.
    >
    > Carl Fogel

    After re-reading the original post, I'm not sure what he meant when saying the wheels didn't feel
    tight. If he meant the wheels had too much lateral (sideways) flexibility, Jim was correct in saying
    tightening the titanium spokes would not do any good. If he meant that the spokes seemed to be too
    loose when pushed sideways by hand, or perhaps plucked like a guitar string, tension will matter.

    The possibly irrelevant point I was trying to make in my last post was that if you push a tensioned
    spoke sideways, but only a small distance, the modulus of elasticity of the material has very little
    effect. Modulus of elasticity is a measure of material stiffness.

    As an example, suppose you have two spokes, one stainless, and one titanium, tensioned to 250 lb
    each, between two perfectly rigid supports. Each spoke is 1.8 mm diameter. The titanium spoke has
    elongated about 1.074 mm from the tension, but the stiffer stainless spoke has elongated 0.632 mm.
    Now push each spoke 2 mm sideways at mid-span. From triangle geometry, each spoke elongates an
    additional 0.028 mm. The tension in the titanium spoke goes up to about 257 lb, and the tension in
    the stainless spoke to about 263 lb. It takes about 7.3 lb of force to deflect the ti spoke, and
    about 7.5 lb for the stainless spoke. For bigger deflections the modulus matters a lot more. If you
    push each spoke 10 mm sideways at mid-span instead of 2 mm, the additional elongation is 0.713 mm.
    Tension in the ti spoke goes up to about 416 lb, and in the stainless spoke to about 532 lb. The
    deflection forces are now about 59 lb for the ti spoke and about 76 lb for the stainless spoke,
    probably now enough to feel the difference.

    The above calculations ignore bending stresses in the thin wire spokes, and assume neither spoke
    starts to yield. I mixed English and metric units only because not many people have much feel for
    how much force a Newton is, but spokes are sold in mm.

    Dave Lehnen
     
  10. Carl Fogel

    Carl Fogel Guest

    Dave Lehnen <[email protected]> wrote in message
    news:<K%[email protected]>...

    [snip]

    > After re-reading the original post, I'm not sure what he meant when saying the wheels didn't feel
    > tight. If he meant the wheels had too much lateral (sideways) flexibility, Jim was correct in
    > saying tightening the titanium spokes would not do any good. If he meant that the spokes seemed
    > to be too loose when pushed sideways by hand, or perhaps plucked like a guitar string, tension
    > will matter.
    >
    > The possibly irrelevant point I was trying to make in my last post was that if you push a
    > tensioned spoke sideways, but only a small distance, the modulus of elasticity of the material has
    > very little effect. Modulus of elasticity is a measure of material stiffness.
    >
    > As an example, suppose you have two spokes, one stainless, and one titanium, tensioned to 250 lb
    > each, between two perfectly rigid supports. Each spoke is 1.8 mm diameter. The titanium spoke has
    > elongated about 1.074 mm from the tension, but the stiffer stainless spoke has elongated 0.632 mm.
    > Now push each spoke 2 mm sideways at mid-span. From triangle geometry, each spoke elongates an
    > additional 0.028 mm. The tension in the titanium spoke goes up to about 257 lb, and the tension in
    > the stainless spoke to about 263 lb. It takes about 7.3 lb of force to deflect the ti spoke, and
    > about 7.5 lb for the stainless spoke. For bigger deflections the modulus matters a lot more. If
    > you push each spoke 10 mm sideways at mid-span instead of 2 mm, the additional elongation is 0.713
    > mm. Tension in the ti spoke goes up to about 416 lb, and in the stainless spoke to about 532 lb.
    > The deflection forces are now about 59 lb for the ti spoke and about 76 lb for the stainless
    > spoke, probably now enough to feel the difference.
    >
    > The above calculations ignore bending stresses in the thin wire spokes, and assume neither spoke
    > starts to yield. I mixed English and metric units only because not many people have much feel for
    > how much force a Newton is, but spokes are sold in mm.
    >
    > Dave Lehnen

    Dear Dave,

    Beware. If you insist on providing such clear, detailed explanations for the nearly innumerate like
    me, we may show no mercy and ask for more--particularly when you pander to us by providing details
    in easy-to-follow pounds.

    So with spokes of titanium and steel at 250 pounds of tension, a 7-pound pull, plus or minus 3%, is
    enough to move the spokes sideways the same tiny distance, 2mmm, not enough to be noticeable to
    most people.

    But to pull the same spokes sideways 10mm takes 59 pounds for the titanium spoke and 76 pounds for
    the steel spoke, about 25% more and probably noticeable to a spoke-tugger.

    The reason is presumably that the greater the sideways bend, the greater the length of the elongated
    spoke, and the greater the difference in force needed to stretch stubborn steel versus easily
    stretched titanium?

    Thanks again for a wonderful explanation.

    Carl Fogel
     
Loading...
Thread Status:
Not open for further replies.
Loading...