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  1. #1
    gebirgsziege
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    Handbuilt Wheelset - Excessive Spoke Tension

    I purchased a set of handbuilt wheels from a well known, reputable, mail order company. When I received the wheels I checked the spoke tension with the Park TM-1 Tension Meter.

    Here is the data:

    Rim Manufacturer's Maximum Spoke Tension: 1200N (122.4 Kgf)
    Spokes: 14/15 (2.0/1.8) Double Butted - DT Swiss Competition (32 Front & Rear 3X)

    Here are the average spoke tensions:

    Front Wheel: 153 Kgf (30.6 Kgf ABOVE MAX)
    Rear Wheel Drive Side: 179 Kgf (56.6 Kgf ABOVE MAX)
    Rear Wheel Non Drive Side: 87 Kgf (Within range)

    These measurements were taken on the center of the spokes (1.8mm) and converted to Kgf with the Park Conversion Table for 1.8mm Round Steel Spokes.

    I contacted Customer Service and they were quick to reply. The wheel builder claims this is a standard build and they build them on the high tension side and after 1-3 rides the wheels loose tension and will be at the optimum tension which will result in a long lasting wheel.

    This seems to be contrary to everything I've read regarding following manufacturers maximum spoke tension specifications. My concern is possible wheel failure and cracks developing around the eyelets. I plan on lowering the tension to the 100-120 Kgf range and re-truing.

    Any thoughts?

    Thanks for your help.

  2. #2
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    chances are that they know what they are doing and I would listen to them on this one. Test the tensions again in 3 rides and contact them if they are still high. I would think they should not loosen much though if they were stress released properly. If they are as well-known as you say then im sure the wheels will be fine as it would be stupid to send out wheels on their part that they think will stress the rim or fail in another way.
    http://tricktrack.freeforums.org/ for fixed trick discussion!

  3. #3
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    Plus, the tension imbalance on the rear drive vs. non-drive seems pretty high (sounds like one of my Campy wheels). If the d.s. had to be that high just to get the n.d.s. to 87kgf, then if you back off the drive side, the n.d.s. spokes might end up with such low tension that you start having problems with spokes loosening and breaking or sending the wheel out of true.

  4. #4
    Senior Member
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    Quote Originally Posted by Metaluna View Post
    the tension imbalance on the rear drive vs. non-drive seems pretty high
    +1
    From the conventional rear 9 and 10-speed wheels that I've checked, the differential is with the non-driveside spokes tension at about 65% of the driveside. The OP's differential is 48.6%. I don't see how the rim could be properly dished with those numbers.
    For the OP, what kind of wheels are these?
    I'm suggesting that you check your numbers. When using the TM-1 be sure to release it onto the spokes slowly. A quick release will cause an elastic rebound resulting in faulty numbers.
    If you decide to reduce the tension I would not reduce it that much.
    Check to see if the rear wheel rim is centered, try reversing the wheel on a truing machine or on the bike.
    Pumping up the tires to normal riding pressure will reduce the spoke tension a bit.

    Al

  5. #5
    cab horn
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    Quote Originally Posted by Jenkinsal2 View Post
    chances are that they know what they are doing and I would listen to them on this one.
    Sorry, they are 100% completley bull****ting. Spokes do not lose tension after riding. The only way this happens is if someone didn't stress relieve the wheels properly after build, whcih means they don't deserve to be called professional wheelbuilders.

    P.S Spokes do not loose tension. They lose tension.

    Leave the tire inflated on the wheel and tension it to spec. A properly trued, and stress relieved wheel will not significantly go out of true or lose tension on the road. This is why there are spoke tensionmeters and specs.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  6. #6
    biked well well biked's Avatar
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    "Handbuilt" wheels from most mail order places usually require some work, at least some fine tuning at the truing stand and often a complete re-tensioning, dishing, etc. My conclusion is that most "handbuilt" mail order wheelsets are really built by not particularly good machines or by humans who either don't know how or don't have time (or both) to properly build wheels.

    The good news is that you can, in affect, buy the parts for wheels much cheaper this way than buying them individually, and if you know how to build wheels yourself you can just look at it as the most cost affective way to buy wheel parts. Pay attention to the spokes, though; make sure DT's or Wheelsmiths are specced, mail order wheels often skimp on the spokes-

  7. #7
    cab horn
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    Quote Originally Posted by well biked View Post
    "Handbuilt" wheels from most mail order places usually require some work
    There are some genuinely professional online only wheelbuilders out there, i'm betting the OP did not order from one of them. And by pro I mean almost zero tension variation when measured using the DT swiss tensionmeter.

    I'm talking expensive, powertap on reynolds wheels here.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  8. #8
    biked well well biked's Avatar
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    Quote Originally Posted by operator View Post
    There are some genuinely professional online only wheelbuilders out there.....
    I agree. That's why I was careful to use the word "most" in the opening sentence of my post.

  9. #9
    cab horn
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    Quote Originally Posted by well biked View Post
    I agree. That's why I was careful to use the word "most" in the opening sentence of my post.
    noted
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  10. #10
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    I think I would reduce the tension.
    I found a finite element analysis of a 36 spoke wheel here: http://www.astounding.org.uk/ian/wheel/
    The take away is that the load is carried mostly by a reduction in tension in the spoke at the bottom. The maximum decrease in tension (in a 36 spoke wheel) is 35 % of the load. The maximum load on the front wheel is the vector sum of the combined weight of the bike and rider and the maximum braking force. If you can brake at .6 g's, the maximum load is 116% of the combined weight. For me that's 116kgf, but I'll use 100kgf because maximum braking is infrequent. It's harder to estimate the difference between a 32 and 36 spoke wheel. I thought it might vary by the ratio of the square of the span between spokes, but that when I applied that to a 20 spoke wheel, the results were obviously wrong. So I just increased to maximum unloading by the ratio of the span. that increased 35% to 40%. So the maximum unloading is 40% of 100kgf, or about one-third of the maximum spec from the manufacturer. That should be fine.
    The rear wheel is a harder problem. The maximum load is about 60% of the combined weight, but pedaling loads the wheel as well. I think I exert at least 100kgf when I'm standing, and working out the torque transfer in my lowest gear, I looks like I'm exerting about 10 kgf on each spoke, and the leading spokes experience that as a reduction on tension. I'm not sure that's right, but I'm not able to do a FE analysis on that. Anyway, the maximum loss in tension in a rear wheel spoke might be 34 kgf (60kgf X .4 + 10 kgf due to pedaling). If you reduced the drive side to 120kgf, the other side would be 60 or less. I'm not sure I would go that low. It depends how you feel about breaking spokes as opposed to cracking rims.
    Measure tension with an inflated tire, which will reduce the spoke tension significantly.
    FWIW I wouldn't use a TM-1 to measure the non-drive side spokes. For low tension spokes, the change in tension due to the load of the instrument is greater, and the tendency of the instrument to bind from friction is greater as well. It's more accurate to measure the drive side, then compute the non-drive side average tension from the geometry of the hub. It's just the ratio of the flange offset from the spoke holes in the rim. The effect of an asymmetrical spoke pattern is negligible. For most Campy hubs, the non-drive side will be 45% of the drive side. Most other hubs will be a little more balanced.
    Hope this helps.
    em

  11. #11
    Senior Member DannoXYZ's Avatar
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    That site is completely wrong with modeling wheel dynamics anyway. Pump up the tyre to operating pressure and re-measure the spoke-tension, you'll find that it drops all around. Then go ride the wheels and break them in for 1000-miles and re-measure the tension. The actual tension-range varies between various rim-models with V-section aero rims taking a lot more than box-section rims. Look up the specs on the rim-manufacturer's website and see what they recommend.

  12. #12
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    Quote Originally Posted by DannoXYZ View Post
    That site is completely wrong with modeling wheel dynamics anyway...
    Can you share your analysis?

    em

  13. #13
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    Quote Originally Posted by DannoXYZ View Post
    That site is completely wrong with modeling wheel dynamics anyway. Pump up the tyre to operating pressure and re-measure the spoke-tension, you'll find that it drops all around. Then go ride the wheels and break them in for 1000-miles and re-measure the tension. The actual tension-range varies between various rim-models with V-section aero rims taking a lot more than box-section rims. Look up the specs on the rim-manufacturer's website and see what they recommend.
    Not counting the effects of tire pressure, is it normal for the tension to drop on a properly stress-relieved wheel just from riding it for a while? What's the break-in mechanism at work? Do the spokes stretch or something? I've noticed this on wheels I've built, but I always assumed it was due to bad stress relieving or tension imbalance (though in my case I'm sure there was some of that too).

  14. #14
    Senior Member DannoXYZ's Avatar
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    What happens with new wheels is the spoke-nipples embed themselves into the eyelets slightly over time. The eyelets themselves aren't fully seated on the rim-surface either. The holes in the flanges actually elongate into ellipses as well. Thus over time, this seating process decreases the distance between the nipple-end and the hub. This takes time and repeated stress->unstress cycles of each revolution. I've noticed this effect more on rims with eyelets compared to rims without eyelets (I worked in a shop for 10-years, raced for 10-years and have built hundreds of wheelsets).

    Also I don't believe it's possible to relieve all built-in stress from the twisted-spoke preload on a wheel without riding it. You can't squeeze parallel-spokes enough with your hands nor can you load up a wheel as much by hand as when you actually sit on it on the bike. The problem with squeezing spokes is you're increasing the tension on them. To really stress-relieve, you have to decrease the tension and the only way you can really decrease tension enough to allow the spokes to untwist is to bend the rim inward enough to do so. That requires adding weight radially to the wheel to compress the rim inwards. Thus riding and hitting enough bumps over time to reduce tension on each spoke is only way to accomplish complete stress-relieving.
    Last edited by DannoXYZ; 08-08-08 at 11:25 AM.

  15. #15
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    Depending on how a wheel is built, it can change a little once you ride it. If the spokes are twisted, they might unwind. (Sometimes you can hear that.) The spokes also seat in the hub. I'm not sure if that increases after the wheel is tensioned, but it seems like that could happen. I don't know how to estimate how much those things would change the spoke tension, but it could have some effect. My guess is the effect is pretty small on a well built wheel.

    em

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