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I have an electric bike with a 500w rear hub. The spokes have broken twice in the last month on the hub end of the spokes.The spokes are bent at the hub end and threaded. This is where they break.

enter image description here

As the bike is under warranty it went back to the supplier for repair and was returned to me with the same type of spokes. Should spokes be made from rod that is threaded at the hub end as it must surely weaken them when bent on the thread. The supplier says it's the first time this has happened but as I've only done 45 km on it since new I don't think that is a good enough answer. What could be the reason for the problem?

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  • Some wheels require spokes to be double-threaded, but they are rare. An example is the DT Swiss Tricon line. Sometimes you get a bad wheel where a few spokes break. Sometimes you get a badly designed wheel (more likely if you go with a bargain/not well-reputed company). It isn't clear what you went with.
    – Batman
    Apr 26, 2016 at 13:49
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    Some pictures might help, especially if you have any of the broken end.
    – Chris H
    Apr 26, 2016 at 14:50
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    You say the spokes break at the hub end, where they are threadded? There should be no threads at the hub end of a normal spoke. Can you please use Edit to post a photo of your wheel/spoke ?
    – Criggie ♦
    Apr 26, 2016 at 23:21
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    Yeah, the description doesn't make sense.
    – Daniel R Hicks
    Apr 27, 2016 at 0:16
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    I've added a crop of the pic from the answer to make the question easier to understand.
    – Móż
    Jun 1, 2016 at 22:40

11 Answers 11

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You're probably OK as the wheel was (hopefully) properly rebuilt rather than assembled on a production line. I assume it was the same wheel, rather than just a swap-out, as the hub motor is an expensive part. It would be more surprising if they did change the type of spokes, as that would mean holding stock of an extra part. The thread depth is a small fraction of the spoke diameter so shouldn't weaken it too much.

There are a couple of e-bike specific issues here which can increase the failure rate:

  • The loading on the rear wheel is much higher than on a normal bike, because of the hub motor, batteries (often near the back) and extra-heavy steel frame (common, not universal).
  • The large hub motor means that the spokes are at more of an angle relative to the rim. Unless special provision is made for this -- which it often isn't -- this increases stresses on the spokes (but not at the end that failed for you). The spokes are also shorter than standard, and the hub motor can make assembly harder.

We have an e-bike and it broke 6 spokes in a day (after probably ~1000km): 1 in the morning, 1 on the way home, then 200m later another 4. After getting new spokes from the manufacturer, we had the wheel properly rebuilt, and it's completely true, with even tension, and no broken spokes since.

If it breaks more spokes, I'll use the first set to patch the wheel up and order good-quality custom cut new ones for the LBS to rebuild the wheel. If not for the warranty aspect I'd suggest you take the same approach.

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  • Two years later it hasn't broken another spoke, despite seeing some fairly heavy service including with a child seat on the back. The owner/mechanic at my LBS is clearly a much better wheelbuilder than FreeGo
    – Chris H
    Apr 26, 2018 at 13:18
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enter image description hereMany thanks for all the replies re my broken spokes. The wheel is a high quality double thickness rim with a Kevlar tyre. The hub alone cost over £500 so it's not a cheap Chinese one. As I stated earlier the hub supplier built the wheel for me using exactly the same spokes. I sent him some motor bike spokes which were 3mm instead of the 2.4 they have fitted but he wouldn't fit them as he said they would invalidate the warranty, and if they failed and I was injured they wouldn't entertain any claims. I haven't any of the old spokes as they went back with the wheel. I have attached a photo of the hub showing the spokes. If it happens again I am going to get it fixed locally at a major bike suppliers. Cheers

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  • Those are unusual spokes - I've never seen them nutted like that at the hub end. Nearest I've seen is a shimano hub that had enlarged nipples at the hub.
    – Criggie ♦
    Apr 30, 2016 at 22:02
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    Yeah, those spokes are so short that it's probably hard to find standard ones that length (and thickness) and if one did there would still be some problems lacing them. The scheme shown "should" work, but the devil is in the details -- making reliable spokes is a fine art.
    – Daniel R Hicks
    Apr 30, 2016 at 22:21
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    This should be edited into the question, rather than posted as an answer. And I've never seen that either, on bikes, motorbikes, cars or anything.
    – Nuі
    May 2, 2016 at 8:22
  • The spoke's elbow (bend at the hub end) is the weakest point anyway, and this is exacerbated if it's at all loose, because then it can flex, and fatigue, and isn't evenly supported by the spoke hole in the hub flange. Some regular wheel builds use soft brass spoke head washers to remove any slack here for this reason. Since these spokes are nutted at the hub, any looseness in the nut will cause the same problem - it's probably worth checking their tightness periodically to make sure none are vibrating loose.
    – Useless
    Jun 26, 2016 at 15:53
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Spokes will always break on the bend as this is the weakest point.

EBikes can generally break spokes or stretch them (in the case of Galvanised spokes).

The size of the hub does not allow an ideal lacing pattern, so bouncing off kerbs, potholes and cobbles will cause the unsprung weight of the hub to put excessive strain on both the spokes and the rim.

I would try a stronger section rim as it is my opinion that the flex in your rim is causing your spokes to fracture.

Cosmetically it may match your existing rim but the spokes you have are stainless steel and as such must have a very high breaking strain as they look to be 2.5mm plus, the flex and diffusion in the rim will cause the spokes to guillotine themselves in the hub holes.

I had similar problems some time ago but I am pleased to say that changing the rim to a much stronger one more suited to my needs cured the problem and I can now report over 3000 miles of trouble free Ebiking.

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    I've never seen a spoke break in the middle, but I have seen then break at the nipple end (ie the rim end) correlated with corrosion. Also, when you changed your rim the wheel was manually relaced. Even reusing the old spokes this will end up with a better wheel than a machine-made one. Most dedicated ebike wheels use slightly thicker spokes too, 12 or 13 gauge instead of 14 gauge. And, welcome to SE Bicycles - sounds like you have good experiences to share.
    – Criggie ♦
    Jun 1, 2016 at 21:43
  • The original spokes on my son's bike with a geared hub broke at the nipple (rim) ends. This was apparently due to the rim being drilled assuming a "normal" hub and the spokes thus approaching the rim at a steeper angle with the larger geared hub, resulting in a slight bend as the spoke entered the nipple. (That and poor quality spokes, of course.)
    – Daniel R Hicks
    Jun 2, 2016 at 12:26
  • Usually people underestimated importance of the rim and tyre pressure, when the rim cannot take the impact (low tyre pressure, lower quality rims) , the energy just travel through the spokes. Perhaps ebike builder should take experiment learned from touring bicycle.
    – mootmoot
    Jun 2, 2016 at 13:11
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I had the same trouble on my rear wheel drive Freego Hawk electric bike. Four spokes broke a week after having it.

The engineers at Freego rebuilt my motorwheel with thicker 12 gauge spokes, and that has solved the problem.

A lot of manufacturers put thin spokes in that are just not strong enough to cope with the stress and load factors of a motorwheel. The problem is made worse with a rear wheel drive hub motor, as you are also peddling, putting added stress on the wheel.

However, rear wheel drive is much safer than front wheel drive, I've been told, as front wheel drive hub motors can lose traction on slippery surfaces, a lot easier than rear wheel drives and spin out from under you causing loss of control.

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    Welcome to Bicycles @richard. I recommend that you take the tour and read the help center to learn more about how our site works. Cheers
    – andy256
    Jun 25, 2016 at 12:27
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    That's interesting because the bike in my answer (below) was also a freego hawk. With identical replacement spokes built by a real bike mechanic it's been fine ever since.
    – Chris H
    Jun 25, 2016 at 14:19
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Since my last info the spokes on my wife's 250w hub also broke 5 spokes. I have now had two sets made at a motorbike shop with proper "J" bend at the motor end in 12 gauge stainless and new rims drilled out to take the bigger spoke nipples.

I am hoping to get the bikes back next week them I am going on holiday to Somerset with the bikes. I will let you know the outcome when I get back.

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Spokes only break when they do not have even tension. Probably, your wheel was not built correctly, leaving the spokes with uneven tension. The effect of this is enormous and can easily make the difference between several broken spokes a day and no broken spokes for several thousand kilometers.

You will know whether your repair shop just swapped in some new spokes, or whether they actually ensured even tension. In the first case, you will have to see them again very soon, in the later case, you will just enjoy your new bike. I hope it's the later.

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I had a lot of problem with standard 2,3 mm spokes and large 1000-1500 watt hub motors. Spokes tend to break after 2000 km run. Which is a few month for me. Problem can be solved with 3x148 mm or 3,5 x 148 mm scooter spokes (for simson, jawa or other Eastern European brand). For this use Altrix Warrior rim 20 mm wide and 30 mm high, ETRTO 559 for 26 " wheel. Watch out because there are 2 types of warrior rims! One of them is not 30 but 20 mm high only which does not work with 148 mm spokes. You have to drill the rim holes for larger spoke nuts. Hub motor needs a new lace. For this you need to drill new holes on it. Use paired spoke hole layout to have spokes in angle instead of radial orientation. Distance between spokes is about 15-20 mm, your choice. After this I went 50000 km with my bike without any problem.

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Personally I'd rebuild the wheel with better thicker spokes. My Ebike wheel had 13 gauge spokes and never broke one, but it was only a 250W motor and it was on the front. If your hub and rim can take more spokes too, consider increasing the spoke count.

Rear wheels take more than half the load of a normal bike, normally around 60% of the whole bike+rider's weight Given you have a heavy motor in there as well.

The motor's weight is also unsprung weight, so it will affect the wheel more than the rider's weight.

As such, don't jump off kerbs/curbs and don't slam into potholes.

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    More spokes wouldn't be a bad thing but the number is often fixed by the motor hub even if you're prepared to have the wheel rebuilt with a new rim. And the motor is an expensive part matched to the electronics.
    – Chris H
    Apr 27, 2016 at 5:42
  • @ChrisH concur - but its a possibility if the hub flange on the motor has more holes. My tandem's drum brake has 36 holes on each side, its currently laced to every second one. So I could have a 72 spoke rear wheel, if the rim suited.
    – Criggie ♦
    Apr 27, 2016 at 8:57
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    I suspect drum brakes for tanderms are high end kit built to a spec, while even if you avoid the cheapest, e-bikes and their components are built to a budget. If we get pictures maybe we'll be able to tell. (btw I upgraded the rear wheel on my hybrid to a 36 spoke touring wheel when the rim failed, because of the load of a toddler seat).
    – Chris H
    Apr 27, 2016 at 9:03
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As many others have said, the wheel needs to be true for the spokes to last, and properly tensioned. It also needs re-true-ing from time to time. I ignored this and I lost a spoke a few days ago. By the way, judging by the photo I have the exact same wheel and motor and I would appreciate the contacts of your seller as I lost mine a long time ago (it's an old out-of-warranty purchase). Or some hints on where to find such spokes. Take care, Florin

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    I doubt you'll get a response, since the person who asked the question hasn't been back to the site since then, nearly two years ago. Also, please do check out our tour -- unlike other sites, we're not a discussion forum and most of your post is really chatting with the (alas, now absent) original poster, rather than answering the question.
    – David Richerby
    Apr 26, 2018 at 14:53
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The Magnum metro+ range over here in the US have a weird pattern and we have had a few into our shop. From what I see often its a design issue more than the substandard materials though if one breaks often more will follow due to the distribution of the forces through the other spokes.

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Pictures will be good.

In electric bikes there is a huge load on the rear spokes, so they tend to loose and break. You have to check the spokes tension every couple of months, adjust it and true the wheel.
Maybe in your country you have better quality bikes than we have, but I really didn't see even 1 bike without this problem. That is why magnesium rims became common.

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  • "check every couple of months" should not be necessary, it means the wheel was badly built or is too weak for the bike. In both cases a rebuild is needed, not ongoing maintenance.
    – Móż
    Apr 27, 2016 at 0:37
  • I working in an LBS, and I think it's a good idea to walk over a LBS every couple of months and ask the workers if the spoke tension is good yet. If it is, they will not charge you for this. You never can tell when exactly it will fail. In such way you will prevent damage and very costly repair. Also E-bikes always should check for rear rim brakes, as they tend to wear very fast. So yes, go to LBS every couple of months.
    – Alexander
    Apr 27, 2016 at 11:46
  • Magnesium rims? I've never seen one, do you have a link?
    – Móż
    Apr 27, 2016 at 12:01
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    Maybe they are popular only in our country :) google.co.il/…
    – Alexander
    Apr 27, 2016 at 16:59
  • ok, one-piece magnesium wheels rather than just the rim. I've seen those in plastic, but wow, magnesium too.
    – Móż
    Apr 27, 2016 at 21:10

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