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  1. #1
    Member bobonker's Avatar
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    Same spoke keeps coming loose

    I'm having a problem with set of custom wheels that I bought. I'll have to dig up all of the specs, but the rims are 25 mm deep with Sapim bladed spokes 20 front and 24 rear.

    The front goes out of true frequently (I've had to true it 4 times now) and every time I check it, it’s one (always the same one) spoke that has lost some tension. I tighten it back down, the wheel goes back to true, but it keeps happening. Should I “overtighten” the problem spoke and then pull it back to true by adding more tension to the opposing spokes?

    I’ve ridden on some crappy roads with them and the rear has been problem-free.

    Thanks!

    Bob

  2. #2
    Senior Member mrrabbit's Avatar
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    Chances are pretty good that you have a rim defect:

    1. Spin the wheel on the bike or stand at a moderate speed. From the side of the rim and wheel - watch the overal depth of the rim. Does it maintain 25mm of depth +/- .5mm or does it seem like the depth varies to as high at 26mm and to as low as 24mm. That would cause there to be 2-4 spots on the rim where you would have an overly loose spokes in a TRUE wheel - AND - 2-4 spots where you would have overly tight spokes in a TRUE wheel.

    2. Check the joint with tire and tube off. The joint should be perfectly straight in the linear sense - and in the lateral sense. If not - this would be a common cause of ONE spoke being overly loose at the joint in a TRUE wheel and ONE spoke being overly tight in a TRUE wheel.

    If either of the above applies...and it's a basic or mid-range rim - you are gonna have to live with it. I.e., you'll have to sacrifice TRUENESS by a couple thousandths and move the priority over to TENSION+DISH.

    If this is a high-end, brand-name rim - i.e., Mavic CXP-33 or Velocity DeepV, this is not acceptable. These kind of defects assumed with standard entry level rims are not supposed to make it out the door on high-end brand-name rims.

    Hopefully this is not just a case of the wheelbuilder coming up short skills-wise...

    =8-)
    4000+ wheels built since 1984...

    Disclaimer:

    1. I do not claim to be an expert in bicycle mechanics despite my experience.
    2. I like anyone will comment in other areas.
    3. I do not own the preexisting concepts of DISH and ERD.
    4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
    5. My all time favorite book is:

    Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life

  3. #3
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    Quote Originally Posted by bobonker View Post
    I'm having a problem with set of custom wheels that I bought. I'll have to dig up all of the specs, but the rims are 25 mm deep with Sapim bladed spokes 20 front and 24 rear.

    The front goes out of true frequently (I've had to true it 4 times now) and every time I check it, its one (always the same one) spoke that has lost some tension. I tighten it back down, the wheel goes back to true, but it keeps happening. Should I overtighten the problem spoke and then pull it back to true by adding more tension to the opposing spokes?
    Ideally you'd only do that if that spot is farther from the hub than the rest.

    The rim may have a slight bend or thickness/other stiffness variation (often at the joint) in it which requires that spoke to be looser than the rest. This can come from damage or imperfect manufacturing.

    If the rest aren't as tight as they should be, that spoke may not be tight enough to keep the nipple from turning. You might check spoke tension (with a tension meter, of which the Park TM-1 is the only model with a consumer friendly price tag around $50) and aim for a reasonable 110kgf average.

    You may need to compromise on radial run-out to get enough tension on that spoke (tighten both it and its opposing members even if they aren't low). It takes a lot of error to be noticeable so that's probably OK.

    You may have put too big a bend in the rim running over a road obstacle to keep it true without loosing spoke tension. If that's happened be glad you have custom wheels with off-the-shelf rims that are readily replaced (use the same spokes).
    Last edited by Drew Eckhardt; 07-28-11 at 07:39 PM.

  4. #4
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    Is it possible that the spoke or nipple is stripped? It may have enough "grab" while adjusting it, but under load or rough ground may pull loose.

  5. #5
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    Hard to say without more information, but my guess is the entire wheel needs to be tensioned correctly. If you have (or have access to) a tensiometer, make sure they're all in the 95-105 kgF range. Or, check the tone when you pluck the spokes -- I think Sheldon likes them all at a F above middle C. Otherwise, true it, then tighten all the spokes 1/4 to 1/2 a turn.

  6. #6
    Member bobonker's Avatar
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    Park TM-1 is on its way.

    Thanks for the input so far.

    Bob

  7. #7
    30 YR Wrench BikeWise1's Avatar
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    Quote Originally Posted by bobonker View Post
    I'm having a problem with set of custom wheels that I bought. I'll have to dig up all of the specs, but the rims are 25 mm deep with Sapim bladed spokes 20 front and 24 rear.

    The front goes out of true frequently (I've had to true it 4 times now) and every time I check it, it’s one (always the same one) spoke that has lost some tension. I tighten it back down, the wheel goes back to true, but it keeps happening. Should I “overtighten” the problem spoke and then pull it back to true by adding more tension to the opposing spokes?

    I’ve ridden on some crappy roads with them and the rear has been problem-free.




    Thanks!

    Bob
    The wheel likely wasn't equilibrated. Pluck the spokes.....the pitches are probably all over the place....

    When I build, not only is every spoke on the same side at virtually the same tension as its neighbors when I am finished (which means there are no spokes carrying more or less than their share of the load) but I use either DT SWISS Spoke Freeze (not permanent) or DT Prolock nipples. That way, my wheels never have mysteriously loosening spokes.

    I suppose it's also possible that the wheels are under-spec'd for your needs, but it's more likely the former.

  8. #8
    Member bobonker's Avatar
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    Ok, I got the Park TM-1. The spoke tensions are all over the place!

    I have to convert all of the the numbers, but lowest number is 1 and the highest is 11 (which is approx 76 kgf).

    Starting from the tube stem hole and going clockwise around the wheel, I got the numbers below. Odd numbered spokes are on the "non-drive" side and even numbers are on the "drive" side.

    1. 1.2
    2. 11
    3. 10
    4. 3
    5. 6
    6. 10.5
    7. 5
    8. 3
    9. 10
    10. 10
    11. 1
    12. 6.8
    13. 11
    14. 4
    15. 3.5
    16. 10
    17. 6
    18. 4.5
    19. 10
    20. 5

    Not sure where to start with this thing. It's pretty much true now, but I know it won't stay that way. I don't have a truing stand. Looks like I need one.

    Bob

  9. #9
    Member bobonker's Avatar
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    For comparison purposes, the trouble-free rear wheel shows a range of .5-3 on the non-drive rear spokes and 8-11 on the drive rear spokes.

    Bob

  10. #10
    30 YR Wrench BikeWise1's Avatar
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    Quote Originally Posted by bobonker View Post
    Ok, I got the Park TM-1. The spoke tensions are all over the place!
    Well, I would set all the spokes to 10 on the tensiometer, and if your wheel is somewhat straight, it may be salvageable. If its a wavy mess, the rim is bent and it's time to consider new.....

  11. #11
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    For the record the wheel will get as straight as the rim is, the guy who build them probably got a lot of troubles with the front one and if the rim is not in good condition and there u have the issues. Between spoke 10 and 11 u have a lot of difference, thats might be the rim joint (expected tho), the funny thing is that at the opposite side (valve) u have the same problem. The rim was used or new?

    New rims can be really bad sometimes but all depends of mere luck. The other thing is the builder's ability. If that was my wheel the 1st thing to do is to just start truing it again and putting some lock compound in the threads that are messing you up. What u can do is to use oil in every spoke thread and retrue the wheel as much as possible.

    If you are in DC i can take a look to your wheel if you like.

  12. #12
    Member bobonker's Avatar
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    Thanks, BikeWise. Is it to typical for front spoke tension to be about the same as the rear tension on the drive side? Purely an educational question.

    Thanks,
    Bob
    Last edited by bobonker; 08-09-11 at 06:12 PM.

  13. #13
    Senior Member mrrabbit's Avatar
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    You need to get the front tension up to the chart equivalent of 95-100 kgf minimum. A few kgf past won't hurt...

    Let's hope fatigue hasn't already set in at the elbows of the spokes...

    =8-)
    4000+ wheels built since 1984...

    Disclaimer:

    1. I do not claim to be an expert in bicycle mechanics despite my experience.
    2. I like anyone will comment in other areas.
    3. I do not own the preexisting concepts of DISH and ERD.
    4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
    5. My all time favorite book is:

    Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life

  14. #14
    Senior Member DannoXYZ's Avatar
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    What kind of rim? You want tension on the high-end of the recommended range. Smaller spoke-counts typically have higher tension. With 20-spokes, you're looking at 125-135kgf. Rear 24-spokes would be in the 120-130kgf range. Get a truing stand and equalize the tension more.

    Front-spoke tension really has no relation to the rear. Front is typically balanced. Rear differential is based upon the amount of dish. With minimal dish, they can be very even and close to the front. With a lot of dish, drive-side will be much higher than front and non-drive-side will be much lower than front. All this is assuming same number of spokes. Once you have different numbers front & rear, it scrambles things even more.

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    The front wheel is essentially being held together by 8 spokes (2 more than the minimum required). The basic question is why the mismatch in spoke tension. It could be due to a bad build, bad rims, bad lacing (unlikely) or non-uniform spoke lengths. The mismatch could be due to your bringing the wheel back into true or it could have come that way from the original build. The mismatch of tensions on the NDS of your rear wheel, which you did not touch, suggests that spoke tensions were not equalized during the build. The question is still why.

    You can get some hint by finding out why the loose spokes are loose. You can determine whether they are loose because of the rim or the build. If it was the build, then the loose spokes nipples will not have engaged all the spoke threads. You can try to sight visually from rim or can measure it with a feeler gauge. If spokes do not come all the way through the spoke (not a good idea), you can use a spare spoke, thread in from the top to determine how far down the spoke tops are. If the loose spokes have engaged fewer threads, then it's most probably a bad build. OTOH, if the reverse is true, then it's most likely a bad rim.

    At this point, your best bet is to rebuild your front wheel from scratch. Loosen the spokes, start with all the spokes loosely tightened the same amount and start rebuilding. Take any hops out first, then the wobbles and gradually add tension.

  16. #16
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    Quote Originally Posted by bobonker View Post
    Thanks, BikeWise. Is it to typical for front spoke tension to be about the same as the rear tension on the drive side? Purely an educational question.
    Yes, that's pretty normal. I'd have to say, at this point, you've got yourself a wheel kit (as opposed to a wheel).

    Normal practice would be to tension and radially true the rear wheel using the drive side spokes -- leave it a little bit low. Then true the wheel laterally (side to side) with the non-drive side. You should end up with a reasonably true, reasonably evenly tensioned, wheel. Stress relieve the spokes, check the true one more time, and go ride.

    BTW, "The Bicycle Wheel" by Jobst Brandt has a detailed description of how a wheel should be built. Between Brandt's book, and Sheldon Brown's web instructions, all you need is a lousy TV show and a few hours to build wheels that will last a long time with minimal trouble.

  17. #17
    coprolite fietsbob's Avatar
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    spokes 20 front and 24 rear
    Bob, Bob, Bob...
    [shakes head] sighs,

    Only 20 spoke wheel I have

    is on the front of my Mk2 Brompton, a 349 16" wheel
    they soon went to 28 hole F&R .. , differentiated, F&R, in spoke gage.


    My impression:
    The wheel perhaps needs to be rebuilt.
    then hanging set on a peg, to be used just for just that time trial/ race day.
    and daily, ride on something more practical to the purpose.
    Last edited by fietsbob; 08-10-11 at 10:05 AM.

  18. #18
    Member bobonker's Avatar
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    I bought a truing stand and with the wheel on the stand minus the tire and tube, the numbers are quite a bit different. When I last checked it, the wheel was on the bike with ~100 psi in the tire. Is it normal for it to change that much with the tire and tube removed?

    1. 3.5
    2. 10
    3. 11.4
    4. 4
    5. 8
    6. 11
    7. 7
    8. 5
    9. 11
    10. 11
    11. 3
    12. 7.5
    13. 11.5
    14. 5.5
    15. 6
    16. 11
    17. 7.5
    18. 7.5
    19. 11.5
    20. 8

    The wheel doesn't seem nearly as messed up (ie, tensions aren't quite as all over the map) with the tire/tube removed.

    Thanks,
    Bob

  19. #19
    30 YR Wrench BikeWise1's Avatar
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    Quote Originally Posted by bobonker View Post
    Thanks, BikeWise. Is it to typical for front spoke tension to be about the same as the rear tension on the drive side? Purely an educational question.

    Thanks,
    Bob
    Generally yes, though some wheels use different spokes front to back, and even on different sides of a rear wheel, with the attendant tension measurement differences.

  20. #20
    Map maker cbchess's Avatar
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    yes tire and tube will change the tension some, but your wheel is still a mess.

  21. #21
    Senior Member
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    What are the thickness dimensions of the spokes? Use the Park spoke gauge in the middle of the spoke and the chart to convert to kgf. The front wheel spokes should all be the same. The rear wheel spokes may have different dimensions from the drive side to the non drive side.
    On all of the wheels I have checked or built the rear wheel drive side spokes have the highest tension, the front wheel spokes have the second highest tension, and the rear wheel non drive side spokes have the lowest tension.

  22. #22
    Member bobonker's Avatar
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    Ok, I messed with it for a few hours and I think I did pretty good for a first timer. Spokes are 2.3mm x 1.0mm.

    New tensions:

    1. 13
    2. 14
    3. 14
    4. 12.5
    5. 15
    6. 15
    7. 12
    8. 12
    9. 16.5
    10. 15
    11. 11
    12. 13.5
    13. 16
    14. 12.5
    15. 13.5
    16. 15.5
    17. 14.5
    18. 13.5
    19. 15
    20. 14

    Average = 13.9 = 101 kgf
    Min = 11 = 76 kgf
    Max = 16.5 = 130 kgf

    Based on the Park instructions "+/- 20% is ok" rule:
    80% of avg = 11 = 76 kgf
    120 % of avg = 16.7 = 133 kgf

    How does that look? The average tension is much higher and in a more acceptable range and I don't have nearly the variance that I had before.

    Bob

  23. #23
    Senior Member
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    1.0 mm spoke? I don't think so.

    It appears that you have a bent rim, tension range is much too wide.

  24. #24
    Member bobonker's Avatar
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    They're bladed. 2.3mm wide x 1.0 mm thick. I'm sure that the rim is bent, but I can't get another before this weekend and the wife and I are doing another century this weekend.

    Bob

  25. #25
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    Quote Originally Posted by bobonker View Post
    They're bladed. 2.3mm wide x 1.0 mm thick. I'm sure that the rim is bent, but I can't get another before this weekend and the wife and I are doing another century this weekend.
    Ok I should have picked up on that, you said they were bladed in the original post.

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