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Bike was new around a year old. 8 of the back spokes broke and it went out of true. I had those repaired with a slightly stronger but spoke but now 2 more have broken including one of the thicker ones and it's out of true again. I have a kiddie seat on the back and am wondering if this is somehow contributing to the breakages. Is there anything I can do to get a very strong spoke? They are all breaking at the j hook location.

user1898525
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  • What side? If the right, have the got damage from a chain drop between the spokes and cassette? – mattnz Nov 28 '18 at 07:53
  • Do verify that nothing (eg, a child's shoe) is getting caught in the spokes. – Daniel R Hicks Nov 28 '18 at 13:14
  • Do you hit a lot of potholes or ride off kerbs or over tree roots? With a child in the seat, that's a lot of shock load on the back wheel. I had a seatpost-mounted baby seat which at least was designed to flex a little going over bumps, but was still much more of a shock than just unweighting the saddle – Chris H Nov 28 '18 at 15:15

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Usually spokes don’t break because they are too weak but because they have too low or uneven tension.

Even tension will distribute the load among several spokes. High enough tension will make sure that spokes are never unloaded completely since spokes should always be under tension. When a spoke is unloaded it can come loose or rub against the hub or other spokes. Even if it rubs or unscrews only a teeny tiny bit on each rotation it adds up. To ride 1000km you need about half a million rotations of the wheel.

Mixing spokes is a bad idea: The stronger spokes will stretch less, which contradicts the goal of distributing the load.

If the wheel is worth it, have it properly rebuilt (or learn to do so yourself, at this point you can’t make it worse). If the wheel is cheap it usually makes more sense to get a new one.

Michael
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  • I agree that even tension is critically important, but spokes actually break from too much tension. The wheel needs to flex and if your spokes are all PING! tight they cannot stretch, so they break. I think that's what you meant with your point on "High enough tension" tough... – markd Nov 29 '18 at 18:19
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    @markd: Yes of course, tension can be too high. Though I think quite often it won’t be the spokes which break but instead the spoke nipples, rim eyelets or hub are going to tear apart. – Michael Nov 29 '18 at 18:27
  • Spoke do normally go because of fatigue, either because they're unloading at normal amounts over millions of revolutions (the way life is) or as mentioned above, more quickly if they're not strong enough to stay unloaded and they're fatiguing more quickly. What's the total load? My buddy who weighed 290 used to break spokes like crazy, as well as destroy headsets. At least until he got a bike with properly-built wheels and a more robust headset. All this assumes a reasonably strong rim. A weak rim will flex more and force the spokes to do more work (or not, and fatigue and break). –  Dec 06 '18 at 00:29
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Without knowing your bike, that's a classic sign of a cheap wheel or built with cheap spokes. The added weight of the kid's seat won't help, but the underlying cause is the wheel and its build.

Your fixes are to replace all the remaining original spokes, or to replace the entire back wheel (hub/spokes/rim) and transfer over the tyre/tube.

If the spokes all broke at the J bend it can be an indication of low spoke tension all round. However when your first spokes were replaced, the bike shop should have tensioned them all better. Tightening all the spoke nipples equally may alleviate the problem or at least slow it down.

Personally I dislike the rear child seats. The ones where the kid sits over the top tube are much nicer for the rider and the child.

Criggie
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    The cost of a complete replacement wheel may be less than the labour cost to redo your existing wheel. Worth checking both costs in your area. – Criggie Nov 28 '18 at 05:50
  • I noticed that after the shop trued the wheel, some of the spoke tighteners near the rim were still a bit loose. Maybe contributed to the 2nd breakage. Would it be worth getting extra strong ones? I will fit myself this time – user1898525 Nov 28 '18 at 05:51
  • @user1898525 check the costs - locally for me a set of spokes alone costs about the same as a cheap wheel. Labour is a significant component, so if you want to do it yourself that will be a saving on cost but an increase in time. Plus you'll need a spoke tool minimum. A truing stand would be nice but I get away using the bike's frame for casual repairs. – Criggie Nov 28 '18 at 05:58
  • I forgot to add it's a 3 speed hub so not cheap to replace – user1898525 Nov 28 '18 at 06:03
  • OK that puts the ball firmly in the rebuild option, in my mind. Explore your local city and see if there's a bike cooperative with the ability to help, with tools and guidance at least. – Criggie Nov 28 '18 at 06:05
  • Why rebuild? I was going just to replace a few spokes and then retrue whilst it was on my bike frame. I have a spoke tool. – user1898525 Nov 28 '18 at 06:11
  • yes - rebuild as opposed to purchasing a complete replacement wheel. Go ahead - it will be a good learning experience. – Criggie Nov 28 '18 at 06:17
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    An e-bike I used to look after broke several of its original spokes in quick succession. After the local bike shop rebuilt the wheel with all new spokes identical to the ones that failed (an odd length, it was either get them from the bike manufacturer or get custom ones cut) none ever broke again. This was a heavy bike with a rear child seat. Don't underestimate the value of having a wheel properly rebuilt, and using all new spokes. – Chris H Nov 28 '18 at 07:07
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    Agree 100% with @Chris - once a spoke or two has failed, the others are stressed. If the wheel was built evenly, the ones that have not failed will be close to failure. Unless you identify a cause of the failure that can be confirmed not to affect other spokes, they all should be replaced (e.g. chain drop damaging right hand outer spokes) . – mattnz Nov 28 '18 at 07:56
  • @Criggie on the other hand, on mail order a set of good spokes and nipples costs under 20€ and you don't have to deal with LBS trying to upsell things. You don't get much of a wheel for that money. – ojs Nov 28 '18 at 10:15
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    @ojs possibly - I'd doubt the quality of 50 eurocent spokes, locally they cost 5x that each for the lowest spec DT spoke. OP needs to find pricing that is relevant to their location though. – Criggie Nov 28 '18 at 18:02
  • @Criggie the price is for DT Swiss at Roseversand. This is why you don't shop locally. – ojs Nov 28 '18 at 18:26