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Poppin' spokes

Old 07-17-12, 02:50 PM
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RideNoCO
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Poppin' spokes

I have rim that's poppin' spokes. Here's story: I popped a spoke the other day; it warped the rim quite a bit but didn't taco it so I took it to LBS, they fixed the spoke and trued it and it looked just fine.
Now, I just popped a different one, saw it before it warped again, nothing odd in the ride and nothing seems to be rubbing it. Same injury, broke right at the bend where it connects to the hub (rivet broke off). So, now I'm wondering:
- Are the spokes just getting old? Should I replace all? Or..
- This rim has had it, should just get new one?

It's a 90s-era rim, Araya brand 700c, seems pretty good quality so i hate to do the latter above. But, strange to me that 2 popped in a week (my other bikes of lesser quality seem to go decades without needing a new spoke). Advice appreciated!
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Old 07-17-12, 03:29 PM
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More will break. If the rim does not have impact damage or accident stress (a good wheel builder/mechanic can determine beforehand) you can just have new spokes laced and properly tensioned, and will still have matching rims. Otherwise you need a new rim and spokes or entire new wheel.
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Old 07-17-12, 04:15 PM
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+1.

When spokes start to break, it can be kind of a zipper effect: one breaks and the others around it take extra stress. Then one of the adjacent ones break because it was overstressed, and when it breaks it overstresses its neighbor, and the broken spokes work their way around the wheel. My rule of thumb is one broken spoke is a fluke, two is a trend and three broken spokes means it's time to rebuild/replace the wheel. Since you had two so close together, I would just do it.
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Originally Posted by bragi "However, it's never a good idea to overgeneralize."
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Old 07-17-12, 04:22 PM
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Rear wheel non-drive side?

That was practically an epidemic in the 90's. 8-speed freehubs made it necessary for wheels to be dished more than previously and, if not carefully built, the non-drive side spokes were under tensioned.

Put me on the list of posters who think that a wheel rebuild is in order.
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Old 07-17-12, 04:51 PM
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I've had the same problem with serially breaking spokes, and the answer was to have the wheel completely rebuilt. Same hub and rim, but new spokes, assembled by a competent wheelbuilder. I've had no trouble since.
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Old 07-17-12, 04:53 PM
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Spokes with insufficient tension break in the "J" bend at the hub flange due to excess flexure. As mentioned above, this most often happens to the spokes on the non drive side of the rear wheel because they are normally the lowest in tension. This condition can be somewhat improved by increasing the tension on both sides of the rear wheel. On 8, 9, 10, and 11-speed wheels I normally set the drive side spoke tension to the maximum recommended by the rim manufacturer. This usually allows the non drive side spokes to have enough tension to avoid breaking and at the same time have the rim centered (properly dished).
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Old 07-17-12, 04:55 PM
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Originally Posted by Doohickie View Post
+1.

When spokes start to break, it can be kind of a zipper effect: one breaks and the others around it take extra stress. Then one of the adjacent ones break because it was overstressed, and when it breaks it overstresses its neighbor, and the broken spokes work their way around the wheel.
No. There's a minimal stress change with a broken spoke.

The problem is that spokes fail due to fatigue, with the numbers of cycles survived dependent on both average stress (which in machine built wheels is mostly the left over stress in parts of the elbows that weren't taken past their elastic limit) and magnitude of the cycle (tension drops in the bottommost spokes in proportion to rider weight as they pass the bottom of the wheel about 750 times per mile; and loose non-drive side spokes see significant stress changes as they flex back and forth in that situation)

The spokes in the same wheel half have seen about the same sort of stress and should be failing about the same time.
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Old 07-18-12, 08:33 AM
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Sorry, significant stress change.
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Originally Posted by bragi "However, it's never a good idea to overgeneralize."
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Old 07-18-12, 09:36 AM
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they fatigue sooner, if under-tensioned.. by now you have to decide rebuild,
price of rim + a buck each for straight gage spokes, from top brands,
or another machine built, hand finished by LBS workers..
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Old 07-18-12, 10:56 AM
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I'm gonna guess it's the NDS rears that are going too, and say you should just replace those ones.

You can totally do this yourself. Take the wheel in the shop, get your 16 or 18 or whatever replacement spokes (and a spoke wrench, if you don't have one), and get them to remove your freewheel or cassette (if it's a cassette, you'll need to take it back in to get tightened, or you can buy the tool). Then go home and replace the spokes. Before you add any tension, it might be an idea to add half a turn to each of the DS spokes so you get a tighter wheel that won't break the NDS spokes in future. Then just do up all the nipples until the thread just disappears, and that's your baseline. After this, you just keep adding a turn or half turn or quarter to every NDS spoke until the rim sits between the chainstays. The wheel may not be quite straight at this point, but if you started off with even tension in the DS, it should be quite round. So now, using the brake pads as indicators, get the rim fairly straight (the DS spokes have more effect on roundness and the NDS ones have more on straightness, so adjustments on DS spokes should be minimal and aimed at evening out tension). Tweak the brake so one of the pads is just touching the rim, then carefully remove the wheel and flip it, and use the difference to get the dish right (the wheel has to be tight in the dropouts). Two or three flips should do it; a quarter-turn usually works as a minimum unit of tension. Before you finish checking dish, but now that it's tensioned up, you should stress relieve the wheel. People's methods vary, but I grab two crossed pairs of spokes through the wheel with one hand, and squeeze hard enough for it to hurt. I go twice around the wheel and call it done. Finish checking dish and trueing, and you should have a straight, round, centred wheel that lasts.
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Old 07-18-12, 11:59 AM
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Originally Posted by Retro Grouch View Post
Rear wheel non-drive side?

That was practically an epidemic in the 90's. 8-speed freehubs made it necessary for wheels to be dished more than previously and, if not carefully built, the non-drive side spokes were under tensioned.

Put me on the list of posters who think that a wheel rebuild is in order.
Yeah, that's interesting, it was rear wheel, non-drive.

I took it back to LBS, I think might take the advice and just buy another one. Thanks!
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