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  1. #1
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    Dyads: bulge at every spoke hole?

    Oh gurus of bulletproof wheels,

    We ride 48-spoke Velocity Dyads on our tandem. I noticed recently that there is a bulge in the rim around every spoke hole on each wheel. I looked at a new, unlaced Dyad, and there are no such bulges as part of manufacturing. The bulges on my rims are certainly a response to tensioned spokes pulling on the nipples.

    Is this typical of Dyads? Or do I have a ticking time bomb?

    I'm attaching a picture.

    Thanks!
    -Greg

    Attached Images Attached Images

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    hors category TandemGeek's Avatar
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    The wheel appears to have been built with the spoke tension set too high. Some discoloration around the spoke holes on clear-anodized Velocity rims isn't all that unusual, but what I'm seeing exceeds the norm.

    Hopefully others who have lived with Dyads (vs adjusting a few) will have some other insights. Lacking a White Knight with Dyads who says "don't sweat it" I don't believe there is much you can do at this point aside from backing the tension off about an 1/8 of a turn around the wheel and trueing "backwards", loosen high spots instead of tightening up low-spots. You'll then want to keep an eye the rim it for signs of a cracking around the spoke holes... which is truly the point at which your rim will be terminal.

    FWIW: 48° wheels are, in some cases, harder to build than 40° and 36° because it is VERY easy to over-tension the spokes. Unfortunately, this lesson is often learned the hard way.
    Last edited by TandemGeek; 11-04-07 at 02:00 PM.

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    more pix...

    Some more snapshots for the record. Note that the neighborhood of every spoke hole looks generally the same. When you change the lighting direction and your viewing angle, different parts of the bulge feature are highlighted. In some views you see sort of a dash in the plane of the spoke. In other views you see kind of a halo around the spoke hole area.

    Yeah, I'm not imagining that this is good. Hope we find that "White Knight", Mark, who can confidently say "they all do that, no worries." (I'm not holding my breath...)

    -Greg
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    Last edited by gregm; 11-04-07 at 06:51 PM. Reason: grammar

  4. #4
    Senior Member zonatandem's Avatar
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    Hold your breath?! Looks like someone was over-zealous with a spoke wrench .
    Next look for cracking of the rim . . . in the meantime I'd be on the lookout for a good deal on rims.

  5. #5
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    Speaking from experience, I'm afraid that's a time bomb.

    I had such wheels laced with 40 spokes which looked like photo #1. I don't have a tensiometer, but I believe that tension was a bit on the low side, at least if I compare to other bikes and to the fact I needed to check truing quite often. Spokes were straight 2.0 mm spokes (14 gauge, I think).

    Due partly to our potholes – avoiding them often means jumping in a 4" hole to avoid an 8" one – tension was very uneven in the spokes and I eventually pulled one spoke on the front wheel. I used the tandem for 1 or 2 weeks with 39 spokes. The rear wheel still had all its spokes, but showed more fatigue, I think. The wheels were only 2000 - 2500 km old!

    I have rebuilt both wheels using the same hubs, new double-butted spokes (for the rear wheel) and Mavic A719 rims.
    Michel Gagnon
    Montréal (Québec, Canada)

  6. #6
    Senior Member skinny's Avatar
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    Have the tension checked with a tensionometer by a bike shop before you turn any spokes. If they do not exceed manufacturer's recommendations, then you may just want to eye check them regularly for signs of cracking. Rims with ferrules that extend through both levels of the extrusion help aleviate this problem.

  7. #7
    hors category TandemGeek's Avatar
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    Quote Originally Posted by Michel Gagnon View Post
    I had such wheels laced with 40 spokes which looked like photo #1. I don't have a tensiometer, but I believe that tension was a bit on the low side, at least if I compare to other bikes and to the fact I needed to check truing quite often. Spokes were straight 2.0 mm spokes (14 gauge, I think).
    Did you compare them to other wheels with the same spoke count or fewer spokes? Was the tension uniformly low or all over the map?

    The reason I ask (rhethorically) is to point out that as you reduce spoke count on a bicycle wheel you must increase spoke tension and, conversely, as you increase spoke count you reduce spoke tension. Just something to keep in mind when comparing tension between wheels with different spoke counts as this is often times why 40° and 48° wheelsets end up being over-tensioned.

    As for wheels going out of true, uneven tension begats uneven tension whereas even a wheel that has uniform tension but is just a little bit low will tend to stay true. If the spoke tension is way low, then yes, the wheels true will always be going out of whack as spoke nipples back-off during use.

  8. #8
    hors category TandemGeek's Avatar
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    Quote Originally Posted by skinny View Post
    Have the tension checked with a tensionometer by a bike shop before you turn any spokes.
    That is if you can find a bike shop that: a) has a qualified wheel builder who, b) knows how to use a tensionometer, and c) has taken the time to contact Velocity to find out what the spoke tension should be on a 48° Dyad rim. This is usually easier said than done and, again, if they aren't familiar with higher spoke count wheelsets commonly found on tandems, going by "feel" or "sound" based on experience gained building 28°, 32°, and 36° single bike wheelsets will get you back to square 1: too much tension for a widely spaced, 48° symetric tandem wheel.

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    Well, now here's a surprise for everyone! Velocity's response:

    Quote Originally Posted by Matthew_from_Velocity
    Hello Greg,

    This is definitely not normal for any of our rims. This is actually cause by
    the wheel build, It looks like the spoke tension is too low. With every
    rotation the nipples are pounding into the rim causing them to bulge.

    We build all of our wheels at the same spoke tension. Spoke tension is
    measured in Kilograms of Force (KGF). We build the front wheel between 105 -
    115 KGF, and the rear between 110 - 120 KGF.

    The rim looks pretty bad, I don't know if it has much life left, or how safe
    it is. I would bring the wheel to a bike shop and get a second opinion. If
    they can get it tensioned and trued, you might be fine for a while. If it
    won't come true you might need a new rim. I which I had a better answer for
    you, but let me know if you have any other questions.'

    Regards,


    MD
    Matthew Dennis
    Customer Service/Sales
    Velocity USA
    Last edited by gregm; 11-08-07 at 09:29 AM.

  10. #10
    Senior Member skinny's Avatar
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    Quote Originally Posted by gregm View Post
    Well, now here's a surprise for everyone!
    At least for tandemgeek.

  11. #11
    Making a kilometer blurry waterrockets's Avatar
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    I would have guessed too high of tension as well. I haven't seen enough rim failures on my own builds to know what causes them -- my wheels usually eventually die of broken spokes.

  12. #12
    hors category TandemGeek's Avatar
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    Quote Originally Posted by gregm View Post
    Well, now here's a surprise for everyone! Velocity's response:
    Six of one, half a dozen of the other.

  13. #13
    Ride it like you stole it WheresWaldo's Avatar
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    I got the same response from Velocity when I asked them about maximum spoke tension. The email response came just a few hours after my query. They seem to be very responsive when it comes to customer questions.
    "Never use your face as a brake pad" - Jake Watson
    The Incidental Cyclist - Cycling in and around Union County

  14. #14
    Terri's Captain RickinFl's Avatar
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    I'm feeling a little uncertain about that response from Velocity- kinda have my doubts about an undertensioned wheel causing rim damage like that.

    Check out this article- http://www.bikexprt.com/bicycle/tension.htm

    And let us know what the pitch of the spoke is. If you are musical in the slightest, you should be able to tell if the pitch is very high or very low. Or compare it to the pitch of a known good wheel. From my reading of the article, a properly tensioned wheel will be close to a certain pitch no matter what the spoke length or crossing pattern.

    Rick

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    Aha! I found my records of tension measurements from when I built the wheels:

    Quote Originally Posted by An_email_I_wrote_in_November_2006
    Quality time with the wheels last night. Goal was to go for higher tension until spokes broke from windup, nipples jammed completely against unthreaded spoke, or nipples started rounding. I got over a full turn on both the fronts (to my pleasant surprise) and driveside rear. Fronts tensiometered at ~130kgf (+/- a couple kgf), and rear drive side spokes are in the one-hundred-teens.
    So, my records indicate that I overshot Velocity's recommended tension in the front wheel (my ~130kgF to their 105-115kgF) and hit their recommended range for the drive-side rears (my "hundred-teens" to their 110-120kgF).

    Curiously, both my front and rear rims show the bulging at every hole. The front was over Velocity's spec, the rear drive side within spec, and -- presumably -- the rear non-drive side below spec on this heavily-dished 140mm 9speed tandem hub.

    How d'ya like that?

    -Greg

  16. #16
    hors category TandemGeek's Avatar
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    Quote Originally Posted by gregm View Post
    How d'ya like that?
    I refer you to my original reply...

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    Quote Originally Posted by TandemGeek View Post
    I refer you to my original reply...
    What, then, is the explanation for bulging on the non-driveside of the rear wheel, which was necessarily below the spec'd tension?

    Or do you think that the Velocity rep does not have proper specifications for 48spoke rim tensions?

    -Greg

  18. #18
    Senior Member Old Hammer Boy's Avatar
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    Makes me wonder if perhaps they had a bad batch of extrusions or a poor hard-anodizing procedure, etc.

  19. #19
    hors category TandemGeek's Avatar
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    Quote Originally Posted by gregm View Post
    What, then, is the explanation for bulging on the non-driveside of the rear wheel, which was necessarily below the spec'd tension?
    If you send me your wheels so that I can physically inspect the rims and squeeze and pluck your spokes I'll be in a better position to answer your question.

    Seriously, I'm old school. You asked what I thought based on looking a 1-dimensional photo with the information you provided in your original posting. I gave you the benefit of what my experience told me when looking at the discoloration on the rim in your first picture. The additional pictures in the subsequent post were a bit more revealling. While one of the rims has less severe maring, all of the photos suggested to me that spoke tension was uniformly too high: call it instinct, a gut feel, an old man's inablity to control his hubris. Moreover, I COULD be wrong. They could be too loose, as others suggested.

    As for the Velocity rep's assessment, he's obviously at the same disadvantage as all of us: we're looking at 1 dimensional photos. Frankly, I'd have to talk with the Velocity rep before drawing any conclusions about his advise, just as I'd really need to put my hands on your wheels to accurately evaluate what happened.

    FWIW: Tensionometers are great, but they aren't the end-all. I own one -- a really old Wheelsmith model -- and it does a few things really well:

    1. It will confirm what my ears and hands tell me about a wheel's spoke tension.
    2. It comes in handy when I don't feel like plucking spokes.
    3. I've always used it when I've worked on someone else's wheel(s) because, well, that's what they expected me to do.
    4. It allows me to answer questions about wheel building using a tensionometer with some degree of first hand knowledge, having used one and all.

    However, my hands and fingers tend to be a much more accurate gauge of spoke tension during the building process as they give me immediate feedback when tension is getting too high. A tensionometer merely confirms what I can usually deduce...
    Last edited by TandemGeek; 11-05-07 at 06:49 PM.

  20. #20
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    I'm surprised

    I'm confused by the Velocity response.On several points.

    1> Does drilling more holes in a rim make it able to withstand more tension? Where I'm going with this is it seems to me that a 32hole Dyad would be properly built with a total of X tension. A 48 spoke Dyad would be properly built with the same total X tension. OR,is the 48 hole extrusion heavier? I bet they use the same extrusion for all drillings.

    My experience building wheels indicates that in a high spoke count wheel,lighter spokes are a must.

    2> I've seen lots of under tensioned wheels brought in by customers.Not one has bulged the rim.They do break spokes tho,due to the load cycling effects.Usually on the non drive side in the rear. The common fix is to use a lighter spoke that remains tensioned through the load cucles.

    3>Not related,but I am starting to use spoke nipple washers on non eyeletted rims. It makes sense to me to spread the load,but things that make sense don't always work out that way. Time will tell.
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    Making a kilometer blurry waterrockets's Avatar
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    [quote=dfcas;5584086]I'm confused by the Velocity response.On several points.

    1> Does drilling more holes in a rim make it able to withstand more tension?

    No. It's the same extrusion in the case of Velocity rims (at least it's intended to be the same extrusion -- I think they could stand to re-tool a little more frequently, given the weight variance I've seen reported in their rims.

  22. #22
    Senior Member skinny's Avatar
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    Quote Originally Posted by TandemGeek View Post
    If you send me your wheels so that I can physically inspect the rims and squeeze and pluck your spokes I'll be in a better position to answer your question.

    Seriously, I'm old school. You asked what I thought based on looking a 1-dimensional photo with the information you provided in your original posting. I gave you the benefit of what my experience told me when looking at the discoloration on the rim in your first picture. The additional pictures in the subsequent post were a bit more revealling. While one of the rims has less severe maring, all of the photos suggested to me that spoke tension was uniformly too high: call it instinct, a gut feel, an old man's inablity to control his hubris. Moreover, I COULD be wrong. They could be too loose, as others suggested.

    As for the Velocity rep's assessment, he's obviously at the same disadvantage as all of us: we're looking at 1 dimensional photos. Frankly, I'd have to talk with the Velocity rep before drawing any conclusions about his advise, just as I'd really need to put my hands on your wheels to accurately evaluate what happened.

    FWIW: Tensionometers are great, but they aren't the end-all. I own one -- a really old Wheelsmith model -- and it does a few things really well:

    1. It will confirm what my ears and hands tell me about a wheel's spoke tension.
    2. It comes in handy when I don't feel like plucking spokes.
    3. I've always used it when I've worked on someone else's wheel(s) because, well, that's what they expected me to do.
    4. It allows me to answer questions about wheel building using a tensionometer with some degree of first hand knowledge, having used one and all.

    However, my hands and fingers tend to be a much more accurate gauge of spoke tension during the building process as they give me immediate feedback when tension is getting too high. A tensionometer merely confirms what I can usually deduce...
    BS alarm.

    With all due respect to those who talk this talk, we in the bike business put up with this for way to long. When the appropriate tools, in this case a tensionometer, were finally made available, it put an end to the customer who comes in and asks if we pluck spokes and listen for consistent pitch in the pluck. I have been involved in music all my life and am by no means tone deaf and plucking spokes for tone or for tension is just too subjective unless there is a significant difference of say 5-10 kgf between spokes. With a tensionometer, we now can build wheels that have all spokes withing 1kgf of each other and do it quickly. This is a reasonable and acceptable tolerance. That is just not attainable by plucking spokes to check tension.

  23. #23
    Terri's Captain RickinFl's Avatar
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    No BS

    You use a transducer clip and your chromatic tuner and you can get the pitch to within a cent or two. I doubt that a tensionometer could come to anywhere near that type of accuracy.

    Then of course, I doubt also that accuracy like that is really necessary. I do think that the folks that talk about checking pitch are really referring to relative rather than absolute pitch, and as a musician, I agree that the method is an excellent way to determine that all of the spokes are at or near the same relative tension, and also to find the ones that are well off from what the rest are.

    Rick

  24. #24
    hors category TandemGeek's Avatar
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    Quote Originally Posted by skinny View Post
    BS alarm. With a tensionometer, we now can build wheels that have all spokes withing 1kgf of each other and do it quickly. This is a reasonable and acceptable tolerance. That is just not attainable by plucking spokes to check tension.
    Again, with all due respect, get off your high-horse for a second and re-read what I wrote instead of extolling the virtues of the tensionometer and poo-pooing how me (most likely you) and most other older folks who've been building wheels learned the craft while also mastering the skills needed for installing and repairing sew-ups... another lost skill.

    As our friend's wheels here demonstrate -- noting that I believe he is a graduate of the Piaw Na wheel building school who likely built this wheel with Jobst Brandt's book by his side along with his trusty tensionometer and conversion tables -- a tensionometer by itself will NOT keep you from screwing up a wheel if you do not have an appreciation for what spoke tension should feel like as you build a wheel. Ignoring what should be obvious signs that a wheel's spokes are getting too tight during or are still too loose after the build and relying too much on the tensionometer readings alone can and usually will get you into trouble.

    As for getting wheels tensioned within 1 kgf of uniformity around a wheel, that sounds pretty cool. I've never seen a conventionally spoked wheel -- at least the variety that the average consumer would buy and use on a tandem -- that would come out perfectly true with the tension being that equal but, again, if y'all have been able to do that quickly good-on-ya.

  25. #25
    Senior Member skinny's Avatar
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    Quote Originally Posted by RickinFl View Post
    No BS

    You use a transducer clip and your chromatic tuner and you can get the pitch to within a cent or two. I doubt that a tensionometer could come to anywhere near that type of accuracy.

    Then of course, I doubt also that accuracy like that is really necessary. I do think that the folks that talk about checking pitch are really referring to relative rather than absolute pitch, and as a musician, I agree that the method is an excellent way to determine that all of the spokes are at or near the same relative tension, and also to find the ones that are well off from what the rest are.

    Rick
    You would have to turn the radio off first in the shops I've worked in, so this method would never work.

    Really, this is way to time consuming and subjective to be used by anyone other then the home mech. Now if you did use electronics to measure pitch, sure, you could get good readings, but otherwise, pffft. You better have some extensive tone recognition training to make plucking a spoke for pitch work.

    And to TG, I just finished a set a wheels for my track bike built with DT 14 straight guage spokes and every spoke is within +.5kgf of 110kgf and I really didn't obssess over it much to get it that close. Building a wheel correctly is all about what you do with it when the nipples first seat against the rim when the tension is low, not what you do with it when the tension is high. But I never could have achieved this kind of balance without a tensionometer.

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