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.
3
-
What side? If the right, have the got damage from a chain drop between the spokes and cassette?– mattnzCommented Nov 28, 2018 at 7:53
-
Do verify that nothing (eg, a child's shoe) is getting caught in the spokes.– Daniel R HicksCommented Nov 28, 2018 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 HCommented Nov 28, 2018 at 15:15
Add a comment
|
2 Answers
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.
-
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...– markdCommented Nov 29, 2018 at 18:19
-
1@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.– MichaelCommented Nov 29, 2018 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).– user36575Commented Dec 6, 2018 at 0:29
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.
-
2The 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 ♦Commented Nov 28, 2018 at 5:50
-
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 Commented Nov 28, 2018 at 5:51
-
3An 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 HCommented Nov 28, 2018 at 7:07
-
1Agree 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) .– mattnzCommented Nov 28, 2018 at 7:56
-
1@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 ♦Commented Nov 28, 2018 at 18:02