Broken spokes

[bazzapage]

I've broken a few spokes now - I don't think I am especially hard on wheels at 80kg (175lb). When I look at the spokes (which all break at the same place) I can't help but think back on my undergraduate engineering days, learning about stresses and strains. The spokes used are think in gauge which along with short length makes the wheel rigid. But then the spoke gets thinner at the thread end, transferring almost ALL the stress on this weak point.
And this folks, is why butted spokes were invented. Thinner in the middle to provide some elasticity, and thicker at the ends to provide strength.
So I think the wheel needs a spoke with a thicker gauge nipple. Am I wrong?

 

[B.M.]

So I think the wheel needs a spoke with a thicker gauge nipple. Am I wrong?

Yes, you can use butted spokes that have the diameter of the thread and thicken about 1 or 2 cm before bending at the other end. I don't have the measures on my mind but could post them later.

I had one broken spoke once and after asking my way around I luckily found a shop close to my working place that is specialized in spokes.

They said that the spokes in the rear wheel of the Turbo seem to be cheap once. In 5 Minutes time they had made 3 butted spokes fitting to my rear wheel, € 2 each. As fare as I know they used "DT Swiss Competition" in black. I just could replace the spoke without changing the nipple.

They also tutored me, if several spokes are broken or are braking one after the other, most probable all the spokes have been to loose for a while. If this is/was the case you should replace the whole set of spokes.

If just one or two spokes are broken, you can replace that single spokes. But in general you should check wether spoke tension is enough altogether.

Here are the measures:

• thread ø 2,3 mm
• thin part of spoke ø 2,0 mm
• thick part ø 2,3 mm
• length 204 mm

Hope this is helpful ;-)

 

[reoutput]

Interesting topic. I have had one broken spoke which broke in the same place as yours...I thought it was because I was hanging the bike by a hook on the rear wheel but this has me wondering. I received a new/reconditioned wheel and have yet to have any spokes break but there very few miles on it as of now. I think the spoke broke at around 1800 miles or so, I will keep this thread updated if anything happens. I am currently running with tires that have a maximum inflation rating of 65lbs.

 

[B.M.]

They also tutored me, if several spokes are broken or are braking one after the other, most probable all the spokes have been to loose for a while.

Because of other reasons Specialized sent a new motor and rear wheel and guess what, all spokes weren’t tensed enough. In any case the tension of the spokes should be checked after the first 100 km when the spokes of a new bike or new wheel are set.

I check by grabbing two crossing spokes between two fingers and pinch them together. If this is possible and I get some creaking sound they are to loose. If I can hardly pinch them, tension is alright.

 

[flymeaway]

So I think the wheel needs a spoke with a thicker gauge nipple. Am I wrong?

The nipple is matched to the diameter of the spoke 1.8mm spokes to 1.8mm nipples, 2,0mm spokes to 2.0 nipples. Broken spokes generally are the result of poor/improper spoke tension. If the appropriate diameter spoke is used for the hub (manufacturer recommendation) and the wheel is properly built and correct spoke tension is followed the wheel should last a very, very long time without failure.

Court J

PS....you might want to consider buying a spoke tension gauge like a Park TM-1. Checking spoke tension with a gauge will assure proper tension. Find out from the manufacturer what the spoke tension should be and check it.

 

[eagamer80]

I've broken my first spoke ever in my life, with my Turbo FLR at reaching almost 1000km/621 miles with the bike, just today at 10km from work. I think this might be a problem of these bikes with the motor and shorter and ill-adjusted spokes. I am not that heavy guy but the road is bumpy almost all the way and I guess this stress the back wheel too much. I never had to replace a spoke ever in my life. I will get this checked ASAP, I wonder if this should be covered by the warranty of the bike, considering that is less than 2 months using it and now this happens. Quite disappointed with the resistance of the spokes considering the amount of money this bikes cost.

 

[flymeaway]

reaching almost 1000km/621 miles

You should be mad, properly matched and installed spokes shouldn't break.

Court J.

 

[eagamer80]

You should be mad, properly matched and installed spokes shouldn't break.

Court J.

I am. This is a major setback for me. Now if I have to deliver it to the store where I bought it to use the warranty, it will be without bike for at least a week. I could do it myself if I had the spare part, but I asked in the bikestores around here and nobody has the size of a spoke for a Turbo which is 205mm long. Damn!! (and even if I had it, then I have the major setback of having to center the wheel, where you would need a special tool to do that, which is not very cheap). Is not as easy as just replace it, then you need to recenter the wheel.
I have the feeling that his is not going to be the last time that this is going to happen.

 

[drcollie]

I check by grabbing two crossing spokes between two fingers and pinch them together. If this is possible and I get some creaking sound they are to loose. If I can hardly pinch them, tension is alright.

The best way to check spoke tension is to grab a small open end wrench with a long handle, like a 10mm size. Then tap each spoke quickly and listen for the "ring". A loose spoke will thud, not ring. Here's a short video I quickly made to show you how:

 

[eagamer80]

Not all spokes should be necessarily hard. The adjustment of each spoke makes the wheel being aligned. Some spokes might be slightly loose than others. Of course, if a spoke is very loose then you might have a problem (but in that case also the wheel will be unaligned because the spokes from one side will be dragging harder than the ones on the other side).

 

[flymeaway]

There are any number of popular misconceptions about spoke tension. There is really only one way to check that your spokes are properly tightened. Buy a tension gauge from a reputable manufacturer like Park or DT Swiss, then consult the rim manufacturers recommended spoke tension for the rim. A properly laced and tensioned wheel has uniform tension on all spokes.

Court J.

 

[bazzapage]

After 3 broken spokes and some tweaking by the LBS my wheel seems to be OK for the last month. Have done another 1000km or so since. Running rear tyre pressure at 55-60psi.

 

[eagamer80]

What is wrong with this bike? Now I broke 2 extra spokes. I just realized about it when I was about to change for better winter wheels today
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You can see the 2 broken spokes here
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And here a closeup:
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It always breaks from the motor side, not from the other extreme. Do you think it might have something to do with the width of the wheel I was using (30-622) or the pressure of the tyres? I assured myself this time to do not inflate them too much. My weight is about 90 kg (198 pounds) and the road is kind of bumpy, but nothing extremely bad. I know the road very well, and I avoid most bumps and stand up to minimize all the impact on the rear wheel. I don't know what else to do, may be buy some shock absorber for the seat post or something.
Luckily this time I have 10 extra spokes I just bought from my bike store the last time they fixed it for me (I said to them... give me them all!!). Sadly I won't be able to center the wheel myself as I don't have the centering tool, but I'll try to manage myself as best as possible, otherwise I'll take it to a bike store again to get it centered. No wonder that Specialized is migrating all the bikes to have a motor in the middle of the bike instead. I think is too much weight and the spokes are not resistant enough. How can we complain to Specialized about this?

 

[Ann M.]

@eagamer, all of the points you mention are possible issues; however, what I would look at first is the spoke tension (along with truing). I see from the last image that there is no beveled edge where the spoke comes out of the motor casing. That's a high stress point for any spoke so the beveling helps reduce that. Another issue could be the type, gauge and brand of spoke. Not all spokes are created equal. A spoke that is too light weight or built with inferior material will break more easily. Butted spokes tend to have more structural strength with added thickness near that motor or axle side and for double butted, also at the nipple end. Either way, if the spoke tension is not correct you will have a lot of breakage. Riding with broken spokes, particularly with the torque from the motor could cause the wheel to collapse while riding. Also make sure that you don't underinflate the tires, that can cause problems, too. Look on the side of the tire for the minimum tire pressure and use that value.

It might be best with so many spoke breakages to get your bike shop to completely relace the motor wheel with better quality spokes.

 

[ebikerider]

I've broken 3 spokes in 3500km, all on the NDS rear and at the threaded end. If another goes then I'll more than likely rebuild the whole wheel with new spokes, something like Sapim Strong.

 

[eagamer80]

The problem of the spokes of this bike keeps me worried. I have not much trust in this bike, especially if I want to go to higher speeds or take a long trip somewhere. Should I have to have a backup spoke all the time with the proper tool to adjust it on the way just in case? I never broke a spoke before so easily, not even with the shittiest bike. I could understand if this happens on a MTB or cycling offroad, but this is not the case. I use it in asphalt in a city at very decent speeds, come on!. These bikes cost 3000 dollars and more, how is possible they do come badly adjusted or with spokes with low quality? @Ann M. you say " I see from the last image that there is no beveled edge where the spoke comes out of the motor casing." Yes, there's no beveled edge, because the beveled edge just jumped off!! 3 times!!! I just adjusted the tension of all the spokes, manually, myself until I had a feeling they were "tense" enough so all spokes will be "dragging" with similar tension. I know that doing a manual adjustment without a proper centering tool is a bad idea, but I need to ride this bike (I use it for commuting to work) and going to my dealer takes half day trip by car to me, so it's really a bummer. I am not happy and I am thinking writing a letter (handwritten, yes) to Specialized telling how angry and disappointed I am that this bike is failing in something so basic. What kind of engineers do they have? They don't have a proper lab with machines to test which kind of spokes they should use for a rear wheel with a heavy engine+the weight of the rider?...pfff... I suspect either the spokes are not fit for the bike, or came badly adjusted from the manufacturer too tight in some extremes, and too loose on others, so some spokes are having more tension than they're capable of resisting.

 

[eagamer80]

Well, today, another spoke (the 4th) jumped off from the rim of the wheel. I just felt it this time. I was lucky because I was just about to go down a very lengthy bridge at quite high speed. I am very likely to have an accident with this bike. I need to contact the dealer again and see what can be done. I will try to convince them to respoke the whole wheel and check the tension in all the spokes as well as the alignment. I am really disappointed.

 

[J.R.]

@Ann M. and @eagamer80 if you look closely the hub is beveled on the inside where it should be for the spokes. The spokes enter the outside of the hub and have a 90° bend on the inside where the beveled edge is needed.

Enlarged screen shot of pic #2 above:



@eagamer80, I broke several spokes one winter, but I commuted many more miles, with a much heavier bike, on heavily rutted trails and paths (off-road). Your damage does seem excessive, given you are on road and not heavily laden. You could try talking to a few well respected wheel builders in your area. Most local bike shops can do repairs, but many don't have the expertise to solve serious wheel problems.

Good luck!

 

[ebikerider]

I am very likely to have an accident with this bike

Very unlikely to have an accident caused by a broken spoke, especially with a 36 spoke wheel. Had no trouble finishing my ride when 2 went in my rear wheel. Yes, it's inconvenient & frustrating but unlikely to be dangerous.

 

[flymeaway]

I will try to convince them to respoke the whole wheel and check the tension in all the spokes as well as the alignment. I am really disappointed

Just my 2 cents. When you have that many broken spokes on a wheel there may be multiple issues. My first observation; since this isn't a radial build why are all the spoke heads pointing out? In a conventional cross build the heads would alternate. Is the drilling pattern on the rim designed for only spoke heads out? Spoke heads usually shear if they aren't set proper in the hub causing excess bend at the J when load is applied. Spokes that break at the nipple are usually an alignment issue. Incorrect or uneven spoke tension can also cause and influence spoke breakage.

Court J.