HELP! Spoke tension for Sestrieres...

Discussion in 'Cycling Equipment' started by Chuck Liu, Aug 9, 2003.

Thread Status:
Not open for further replies.
  1. Chuck Liu

    Chuck Liu Guest

    I recently brought a Park tool Tensiometer. I checked the spoke tensions on my Rolf Sestrieres and
    found out that the tensions were all over the place... After playing with the front wheel for hours,
    I still couldn't get each spokes to have even tension AND roundness! How much spoke tension should
    be on the front wheel? ....the non-drive side rear? ....the drive side rear?

    Any help is appreciated! Currently, I tried to get the tension of the front spokes to about "15."
    (these are revolution spokes). Is this too high/low a tension?

    Help! anybody? These are the total pair of wheels that I have currently and I need them for a Sunday
    century. I guess I will be tweaking the rear wheel the whole day tomorrow :(
     
    Tags:


  2. David Kunz

    David Kunz Guest

    Chuck Liu wrote:
    > I recently brought a Park tool Tensiometer. I checked the spoke tensions on my Rolf Sestrieres and
    > found out that the tensions were all over the place... After playing with the front wheel for
    > hours, I still couldn't get each spokes to have even tension AND roundness! How much spoke tension
    > should be on the front wheel? ....the non-drive side rear? ....the drive side rear?
    >
    > Any help is appreciated! Currently, I tried to get the tension of the front spokes to about "15."
    > (these are revolution spokes). Is this too high/low a tension?
    >
    > Help! anybody? These are the total pair of wheels that I have currently and I need them for a
    > Sunday century. I guess I will be tweaking the rear wheel the whole day tomorrow :(
    >
    >

    I don't specifically know the Rolf wheels. You didn't specify the units of the device.

    BUT, that aside, I build my wheels to about 100-120 kg on the inset side (disc on the front, free
    hub on the rear) and whatever is needed for the rim to be centered on the other side -- usually
    about 70-80 kg.

    Your problem is probably one of experience. You need to balance the tension across several spokes.
    You can't just put all of the spokes at the same tension and have the wheel be perfect -- or machine
    built wheels would be great! Rims just aren't that perfect! A 10% variation is typical.

    What you need to do is to find the tight spokes by plucking them and listening to the tone. Check
    for matching loose spokes nearby. Loosen the tight spoke and tighten the loose spoke to bring the
    wheel back in true. Repeat this until the tension is even and the wheel is true. Also check across
    the wheel for matching tight spokes on each side that both need to be loosened. If you have a welded
    rim, you won't be able to do this around the weld -- just do your best. When you've completed this,
    then you'll probably need to bring the whole wheel up to tension. At this point, you can probably
    just put a 1/2 or 1/4 turn on each nipple all of the way around and have the wheel stay in true
    (check it though :), and you may have to adjust the centering). Also, every so often, take the wheel
    off the stand and put hard taco'ing pressure on it to help the spokes seat.

    When you're done, put the handle of a screwdriver between the spokes and twist it hard to cross the
    spokes harder. This seats the spokes and bends the spokes a little at the crossovers making them
    more resistant to breaking.

    Some people put a little black dot with a magic marker on each spoke to check for twist. Then, if
    the spoke winds-up instead of tightening, you know and can account for it, and take the twist back
    out after the adjustment.

    Make your adjustments in small increments: 1/4 - 1/2 turn.

    When you're building a wheel, you find the high / out of round spot. Check the spoke tension on the
    nearby spokes on both sides by plucking them and listening to the tone. Adjust the spoke(s) that
    are the most out of tension with their neighbors -- either tighter or looser depending on which way
    the wheel needs to move. Towards the end of truing, a spoke 5 spokes away from the out-of-round
    spot is the one that pulls it in. Every so often, go all of the way around to check to evenness of
    tension (by plucking and listening to the tone) -- and measure a couple to see how close to full
    tension you are.

    David
     
  3. Chuck Liu

    Chuck Liu Guest

    Thanks David! Yes, I have absolutely no experience in wheel building. After tweaking the wheel for a
    whole day, I was able to disassemble the spokes and retensioned the whole wheel. To make things
    short, I was able to get the drive side to an average tension of "17.04" (about 97kgf) with a
    deviation of 2%. Before mounting the tires, the tension was at around "19" (about 117kgf). Somehow
    after mounting the tires and "tacoing" it a bit, the tension dropped a little. The non-drive side
    had an average tension of
    7.5 (below the conversion scale. maybe in the 40s kgf range) with a deviation of 21%! Again, the
    tension was a little high prior to mounting the tires.

    Does these values sound fishy? Perhaps it's a dangerous wheel to ride on? The tension difference
    between the two sides is 100%. I don't know it this is normal or not. It's a low spoke count
    wheelset (24 spokes in the rear and 20 in the front).

    Again, thanks! I guess I will head out and give it a spin tmorrow with caution.
     
  4. David Kunz

    David Kunz Guest

    Chuck Liu wrote:

    > Thanks David! Yes, I have absolutely no experience in wheel building. After tweaking the wheel for
    > a whole day, I was able to disassemble the spokes and retensioned the whole wheel. To make things
    > short, I was able to get the drive side to an average tension of "17.04" (about 97kgf) with a
    > deviation of 2%. Before mounting the tires, the tension was at around "19" (about 117kgf). Somehow
    > after mounting the tires and "tacoing" it a bit, the tension dropped a little. The non-drive side
    > had an average tension of
    > 7.5 (below the conversion scale. maybe in the 40s kgf range) with a deviation of 21%! Again, the
    > tension was a little high prior to mounting the tires.
    >
    > Does these values sound fishy? Perhaps it's a dangerous wheel to ride on? The tension difference
    > between the two sides is 100%. I don't know it this is normal or not. It's a low spoke count
    > wheelset (24 spokes in the rear and 20 in the front).

    I've never measured a wheel with the tire on it :). It'll put pressure all of the way around and I'd
    expect it to reduce the tension -- unevenly since the rim isn't perfect. You didn't post the
    pre-tire tension of the non-drive side spokes, so I can't comment there. BUT, it sounds like you did
    everything right -- I'd ride it! Then, remove the tire and check it again :).

    BTW, the stress relieving step (with the screwdriver handle) is an important one! Don't forget it.

    > Again, thanks! I guess I will head out and give it a spin tmorrow with caution.
    >

    David
     
  5. Chuck Liu

    Chuck Liu Guest

    > I've never measured a wheel with the tire on it :). It'll put pressure all of the way around and
    > I'd expect it to reduce the tension -- unevenly since the rim isn't perfect. You didn't post the
    > pre-tire tension of the non-drive side spokes, so I can't comment there. BUT, it sounds like you
    > did everything right -- I'd ride it! Then, remove the tire and check it again :).

    Mounting the tires and pumping the pressure to about 120psi seemed to decreased the tension by about
    20kgf. So I would say the pre-mounting tension on the non-drive side was in the 60s kgf range with
    similar deviations. The front wheel (radial lacing) tension also dropped similarly after mounting
    the tire. I had the front at about 82 kgf pre-mount. Should I increase this to 100-120kgf? It seems
    that these factory built wheels came seriously under-tensioned and uneven.
    > BTW, the stress relieving step (with the screwdriver handle) is an important one! Don't forget it.

    Yes, I was able to do that with a handy tire lever. How do you stress-relieve a radially laced wheel
    with no cross pattern? Another detail I left out was... instead of using spoke-prep to lock the
    spokes in place, I used medium strength lock-tite.
     
  6. David Kunz

    David Kunz Guest

    Chuck Liu wrote:
    >>I've never measured a wheel with the tire on it :). It'll put pressure all of the way around and
    >>I'd expect it to reduce the tension -- unevenly since the rim isn't perfect. You didn't post the
    >>pre-tire tension of the non-drive side spokes, so I can't comment there. BUT, it sounds like you
    >>did everything right -- I'd ride it! Then, remove the tire and check it again :).
    >
    >
    > Mounting the tires and pumping the pressure to about 120psi seemed to decreased the tension by
    > about 20kgf. So I would say the pre-mounting tension on the non-drive side was in the 60s kgf
    > range with similar

    I've run them there with no problems (and no spoke prep :)).

    > deviations. The front wheel (radial lacing) tension also dropped similarly after mounting the
    > tire. I had the front at about 82 kgf pre-mount. Should I increase this to 100-120kgf? It seems
    > that these factory built wheels came seriously under-tensioned and uneven.

    Normal -- that's why I build my own wheels :).

    >
    >>BTW, the stress relieving step (with the screwdriver handle) is an important one! Don't forget it.
    >
    >
    > Yes, I was able to do that with a handy tire lever. How do you stress-relieve a radially laced
    > wheel with no cross pattern? Another detail

    All you can do is to seat the spokes. I've read that you grab spokes next to each other and
    squeeze hard. I've never run radial because they're not as strong and I'm a clydesdale :) (and I
    run disc brakes and radial lacing has alot less resistence to the rotational stress put on them by
    the discs).

    > I left out was... instead of using spoke-prep to lock the spokes in place, I used medium strength
    > lock-tite.

    If the wheel's built right, you won't need spoke prep. I haven't used it in a while and should be
    collecting on a bet with my LBS -- they bet me that I'd be sorry if I didn't use it, but my wheels
    typically don't need truing without the help of spoke prep :). AND if you do use it, it'll make the
    rim harder to true-up later if it drifts or you hit a big pot hole :). You may have problems with
    the spoke winding up instead of the nipple turning on the spoke. The only time that I'd consider
    spoke prep is if I was using alloy nipples on a mountain bike or a bike that will see rain. Alloy
    nipples have a habit of bonding themselves to the spokes when they get wet...

    David
     
  7. Jobst Brandt

    Jobst Brandt Guest

    Chuck Liu writes:

    > Mounting the tires and pumping the pressure to about 120psi seemed to decreased the tension by
    > about 20kgf. So I would say the pre-mounting tension on the non-drive side was in the 60s kgf
    > range with similar deviations. The front wheel (radial lacing) tension also dropped similarly
    > after mounting the tire. I had the front at about 82 kgf pre-mount. Should I increase this to
    > 100-120kgf? It seems that these factory built wheels came seriously under-tensioned and uneven.

    Tension should reduce uniformly around the wheel and it's not from air pressure pressing against the
    rim but rather from the bias play in the tire similarly to what tubular tires do when inflated, the
    force that holds them on the wheel with the help of rim glue to prevent separation under exceptional
    side loads that occur primarily in a side skid or a crash. The formula and description of this
    effect is in "the Bicycle Wheel" as are many other arcane effects of the wire spoked wheel.

    >> BTW, the stress relieving step (with the screwdriver handle) is an important one! Don't
    >> forget it.

    > Yes, I was able to do that with a handy tire lever. How do you stress-relieve a radially laced
    > wheel with no cross pattern? Another detail I left out was... instead of using spoke-prep to lock
    > the spokes in place, I used medium strength lock-tite.

    I don't recommend using hammer handles or old pedal cranks because this can bring excessive loads on
    individual spokes and in some cases leave kinks in the spoke that could lead to long term failures.
    The method I prefer is to grasp adjacent spokes on the same side of the wheel and squeeze them
    together forcefully. If you have insufficient callous on your hands, leather working gloved can
    furnish protection. This method works for most wheels, even ones with paired spoke, where the pairs
    are grasped. A 14 or 16-spoke wheel with staggered spoking has the spokes to far apart to do this.
    In that event the primitive method of laying the wheel on its side and using a tennis shoe to step
    on each spoke at midspan, carefully, works best.

    The 24-spoke Sestriere can be stress relieved manually by squeezing the pairs together. As was
    mentioned, this is an important part of the build.

    Jobst Brandt [email protected] Palo Alto CA
     
Loading...
Thread Status:
Not open for further replies.
Loading...