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Old 06-05-07, 04:26 PM   #1
wroomwroomoops
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On spoke reusability

I know that there's some common wisdom that says, if a wheel has some broken spokes, the others are probably useless. Is that certainly true? What if only 2 out of 36 spokes are broken? And can a visual or other inspection of the other spokes, reveal whether they are close to snapping?

How about an old but otherwise healthy wheel, would you reuse those spokes?

I aprecciate any and all answers, arguments, analyses from any point of view. I'd like to see this questtion discussed from as many angles as possible.

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Old 06-05-07, 04:46 PM   #2
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The "common wisdom" you mention is ridiculous. I worked for over 20 years as a mechanic and repair manager and I have never heard that theory, nor is it valid. One of the most common repairs in a shop is spoke replacement, and I seldom saw further problems from wheels which had that procedure. Spokes can break for a variety of reasons, and it is the cause of the breakage that determines to what degree you should trust the remaining spokes. I would suspect the integrity of other spokes in a wheel if:

1. The spokes are loose due to lack of maintenance. That puts an enormous stress on individual spokes instead of them sharing the load as designed.

2. The spoke breakage happened on a relatively new wheel under normal usage, esp if more than one spoke broke either at the same time or one after another. Likely either the spokes are defective or the hub is a "spoke breaker" due to bad design (too little support for the spoke at the head).

3. The spokes have been severely overtensioned. They are not necessarily in danger of breaking if detensioned, but may be difficult to true due to rounded nipples flats and damaged threads.

4. On an older wheel the owner has had serial breakage, especially on the drive side. Fatigue has probably set in, and given the difficulty of drive side replacement it's probably best not to continue to try saving the wheel/spokes.

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Old 06-05-07, 04:46 PM   #3
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I'm not exactly a "spokesman" for this topic but if you have a relatively new wheel that pops a couple of spokes, that would not mean that the remaining spokes are bad but rather that there is unequal spoke tension causing the spokes to break in the first place. This could also be caused by a damaged rim. My personal experience with wheels that break spokes is that it is akin to whackamole, you fix one and another one breaks. I don't recommend building a new wheel with used spokes since they are stretched.
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Old 06-05-07, 04:55 PM   #4
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The old "rule of thumb" used to be when the third spoke breaks, relace the wheel.

Before the current DT/Wheelsmith stainless steel spokes were common, plain Cd or Zinc plated steel spokes had a relatively low service life and would start to break after fatigue got to them. Usually a first broken spoke was followed by several other in a short time.

A typical cause of spoke breakage is low build tension. Spokes break from fatigue and low tension causes a high amount of stress cycling and even complete detensioning that really speeds up the fatigue process. Excessive high build tension normally leads to rim failure, not spoke failure.
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Old 06-05-07, 05:11 PM   #5
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Quote:
Originally Posted by BikeToWork
... a relatively new wheel that pops a couple of spokes, that would not mean that the remaining spokes are bad but rather that there is unequal spoke tension causing the spokes to break in the first place. This could also be caused by a damaged rim. ....I don't recommend building a new wheel with used spokes since they are stretched.
Yes the spokes could indeed be bad (not everyone rides a bike shop quality bike) and uneven spoke tension is not possible on a true wheel unless the rim is damaged. On a new wheel spoke breakage under normal use means bad spokes or bad hub design, with low spoke tension a distant third.

As for rebuilding with "stretched" spokes, it depends on the circumstances. Admittedly there are not a lot of times I would recommend it but if the relace is due to a rim defect or non-impact damage, so that the spokes have not been unduly stressed, there is no problem with reusing the spokes by just transferring to the same model rim or one that takes the same spoke length.

If someone can show me otherwise I would be glad to listen.

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Old 06-05-07, 08:24 PM   #6
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If I have a wheel in with a broken spoke in the usual spot, either the J-hook or the end of the threading, I replace it, check the wheel out and tell the customer that should it break another in the near future, they should rebuild the wheel because it is likely to continue breaking spokes until they damage the rim and need to replace that as well.

If a wheel breaks a spoke anywhere but the J-hook or threading, I tell them the best thing is to rebuild it as this is a sign of quality problems with the spokes. ((I will still replace the broken one if that is what they want)

If someone tweaks a rim I will rebuild, with the same type(new) rim(or same ERD rim), using the old spokes. I will not delace a wheel to reuse spokes because they might be the right size for a new build. But I need to keep my boss in the black.
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Old 06-06-07, 12:19 AM   #7
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Wow, excelent posts! This is an example when BF/BM truly shines!

How do you know the rim is bad? If you remove the spokes and the rim is laterally true and circularly within a few millimeters, is that rim OK or can it still be considered bad for some other reason, invisible to the naked eye?

I don't know the cause for the two missing spokes. I guess a bike mechanic would suggest not to reuse the other spokes, to be on the safe side?
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Old 06-06-07, 03:30 PM   #8
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Aside from obvious cracks, if the wheel has been bent pretty bad or an unlaced rim will not lay flat I consider it bad. You could straighten it in a pinch but better to get a new rim

If you got a wheel that is missing two spokes, it is worth it to replace them and see how it turns out. At the worst you will be out a couple of bucks and a half hour.
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Old 06-06-07, 03:33 PM   #9
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If you don't know the history of the wheel and the spokes are stainless it's a tossup in my opinion. Which side you choose depends on weighing possible cost savings vs. possible inconvenience and time/expense of another build. Remember you can only reuse the spokes if the new rim takes the same length.
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Old 06-06-07, 03:39 PM   #10
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Quote:
Originally Posted by Rev.Chuck
Aside from obvious cracks, if the wheel has been bent pretty bad or an unlaced rim will not lay flat I consider it bad. You could straighten it in a pinch but better to get a new rim
If you got a wheel that is missing two spokes, it is worth it to replace them and see how it turns out. At the worst you will be out a couple of bucks and a half hour.
Quote:
Originally Posted by cny-bikeman
If you don't know the history of the wheel and the spokes are stainless it's a tossup in my opinion. Which side you choose depends on weighing possible cost savings vs. possible inconvenience and time/expense of another build. Remember you can only reuse the spokes if the new rim takes the same length.
Thanks again, guys. Yes, I will definitely try to rebuild the wheel.

To cny-bikeman: the spokes from the wheel with 2 missing spokes, are zinc-plated, but still rather good looking.They don't look considerably worse than the new stainless spokes of the same length I have. They seem, however, thinner.

I don't mind doing a second rebuild, if this one fails because of fatigued spokes. I like building wheels.
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