Spoke Strentgh (My spokes are breaking like mad...)

[Bitmaximus]

Hey guys, it seems like everytime I hit the throttle/go over a bump a spoke breaks...!

It's annoying as hell, and I want it to stop !

What are the solutions, is my wheel just built like crap or is this something everyone experiences with their ebikes?

Are there any one piece solid wheels with hub motors built in availible? (No spokes)

Are there heavier duty wheels that wont do this?

Help! Thanks

 

[Kin]

I don't know much about spokes, but you might want to include

-Wheel size
-What motor you're using
-If you know, what gauge spokes you're using
-Rider weight (not sure if this matters that much, as long as the spokes are properly done).
-Who is fixing the spokes when they break (You? Local bikeshop? Someone with experience?)

From what I've read, the proper amount and balance of tension is very important, as well as the weave and gauge. But, larger spokes are not necessarily better, compared to properly. Anyway, I guess someone with more knowledge will chime in soon.

 

[Ykick]

My stock Chinese 9C rear wheel required constant truing and tensioning. Around 1500 miles it eventually died from a pothole at 25-30 MPH so I rebuilt it with a Mammoth Fat eyelet rim and I think Sapim stainless 13/14ga butted spokes.

I might sound like an advertisement but I can't say enough about the difference building using these components makes. Another 1500 miles and no need to touch a spoke wrench yet. Amazing difference and don't let the 13/14ga scare you into believing the wheel won't be strong enough. I'm 240lbs and ride rough roads with not signs of trouble using this wheel build.

I won't even bother buying Chinese laced wheels anymore, not worth the trouble constantly truing/tensioning and eventually having spokes break.

 

[Bitmaximus]

26" Wheel
Commercial prebuilt ebike (VELEC)
12 gage spokes
240Lb 6"3""
Motor is rated 350W
Havent had too long, not origional owner of the bike, don't know how much origional owner rode the bike.
Local bikeshop replaced some spokes for me.

I like the sound of that Ykick, sounds like just what im looking for, indestructable back wheel, I'd also like to get a new motor, probably a 9c... Any idea how much this back wheel would cost, and where I could source the spokes, rim and a 9c motor not built into a rim?

 

[Drunkskunk]

what you need is quality spokes. A new and high quality rim would certianly help, but its the spokes that are the real problem. Most of these chinese built hub motors come with 12 or 13 gauge spokes made out of a realy soft metal. they stretch and break easily, and I've found they cut easily one handed with small wire cutters.

A good quality spoke in 13/14 or straight 14 gauge is actualy thinner, but a quality spoke will be at least twice as strong as the soft chinese 12-13 gauge. I've found using the same wire cutters I have to use both hands and struggle to cut a cuality DT swiss 14 gauge spoke. A 14 gauge spoke is strong enough to be run on the X games bikes, or Professional DH race bikes. It will be more than strong enough for your bike.

 

[Chalo]

If your spokes are breaking frequently at the elbow and the wheel is nearly new, then the spokes are defective.

If your spokes are breaking frequently at the elbow and the wheel has accumulated some significant mileage, you're dealing with metal fatigue stemming from poor assembly technique.

If your spokes are breaking frequently at the threads, the wheel was originally laced in an incorrect patten, such that the spokes kink where they enter the nipple.

Whichever of these it is, the problem will persist until you have the wheel rebuilt with good spokes by someone who knows what he's doing.

There is some small chance that the way you are mounting or dismounting the bike is abusing your wheels. To prevent this, you must avoid putting your weight on the bike when it's leaned over to the side. This probably isn't the issue, but it can be cured if it is.

There is a fallacy that spokes which break need to be stronger. In fact, almost all non-defective spokes are at least four times stronger than they need to be to withstand the forces they endure. They break from metal fatigue, which is cracking that occurs at stress levels below what it takes to deform the spoke. It's largely preventable by using adequate spoke tension and performing a step called "stress relieving" (which is momentary overtension) on assembly. But once it's a problem, all the spokes in the wheel have already been affected and are likely to break.

To be fair, hub motors have some peculiar characteristics that make wheels built with them less reliable and weaker than wheels built on normal hubs. They are so large in diameter that it can be difficult to come up with a lacing pattern that doesn't make the spokes enter the rim at a harsh angle. Their flanges are often made from steel (which is hard on spoke elbows compared to aluminum) and are usually placed very close together, and that gives side forces on the wheel extra leverage with which to overload spokes and break them.

More than likely, your problems will be solved if you have an experienced bike mechanic rebuild your wheel with new, good quality spokes and ideally a better rim too. You don't need to mess around with extra thick spokes (which cost extra, further complicate lacing, will not stay tight, and increase the likelihood of cracking your rim) if you get a competent professional build.

Chalo

 

[recumbent]

If you hear a "clicking" sound from your wheel, stop and tighten all your spokes 1/4 turn, loose spoke is a dead spoke.

But "ykick" is absolutely correct. The same thing happened to me, i had one bad Chinese built wheel kept pulling spokes through the nipple threads. So i replaced them all with good quality Sapim type spokes and never ever had problems for 5,000kms or (3,000 mi) . Still going strong.

You must however keep them trued, or tightened fairly snug, because they go loosey the first few hundred miles when new. Good luck, rebuilding a wheel is easier than you think, if I can do it anybody can words of wisdom for the poor.

 

[Kingfish]

The beefiest spokes that are commonly available and match well with 9C and bicycle rims are 12-gauge (2.0-2.3mm) in diameter.

• JRH offers up good product,
• and I also suggest Wheelbuilder’s Sapim Single-butted tapered spokes.

Last summer I was in a pinch trying to get my wheels repaired (actually I had to swap rims & hubs) and found a local bike shop that rolled their own: These were not tapered; instead they were 2mm across the entire length, however they worked out quite well, particularly for the heavy loads my ride endured when On The Road Version-2, and I did not break a single spoke (unlike the year before when I broke 5 when attempting the same feat ).

Finally, Wheelbuilder suggested not to exceed 120kg of tension when tightening them down.

Hope this helps, KF

 

[neptronix]

Gee, who built this wheel? a well known vendor or some eBay vendor who is pushing the stuff by the crate straight outta China and has no involvement?

Were you told that you needed to get this wheel trued after a short period of riding by this vendor or anyone else? machine-built hub motor wheels are often a little off by the factory and the alignment only gets worse over time unless they are trued ASAP and periodically checked just like any other bike wheel.

 

[Chalo]

Finally, Wheelbuilder suggested not to exceed 120kg of tension when tightening them down.

Maximum tension depends on the rim. Some rims (road ace stuff we don't need to worry about) are rated as low as 85kgf, while others are rated as high as 140kgf. Many, perhaps most, have no specified rating at all.

The rule of thumb in the bike shop world is 100kgf for everything. I prefer to use more with very sturdy rims, or wheels that I know are going to carry a heavy load. Less with cheap steel rims or ones that are likely to pucker or crack at moderate tension.

Chalo

 

[liveforphysics]

Large spokes 11awg, 12awg are impossible to make a proper wheel using a bicycle rim. If you want to use a motorcycle rim, then perfect, you can get them to the tension where it can function to distribute stresses, in a bicycle rim, the spoke simply will pull through the rim or collapse the rim well before you can apply the force needed to get a 11-12awg spoke to stay in tension.


IMHO, 14awg spokes are the ticket for making the strongest possible wheel using a bicycle rim. I know that a wheel made with 14awg spokes can handle over 700ft-lbs of torque and survive bumps, even speed bumps and potholes at >60mph. (though your legs might not)

If you use a spoke thicker than you can pre-tension enough to always keep it high in the elastic strain zone, your wheel can't distribute stresses and it will fail.

 

[liveforphysics]

Also, unless you just got some total garbage defective spokes, it's never a spoke failure (this is a symptom of the problem, not the problem), and the solution isn't stronger spokes. It's a wheel stress distribution failure, and the solution is whatever allows the wheel to distribute stress (often thinner spokes).

 

[Chalo]

Also, unless you just got some total garbage defective spokes, it's never a spoke failure (this is a symptom of the problem, not the problem), and the solution isn't stronger spokes. It's a wheel stress distribution failure, and the solution is whatever allows the wheel to distribute stress (often thinner spokes).

Unfortunately, there are plenty of crapz0rz spokes out there, and OEM Chinese wheels for specialty markets is a great place to find them. And, well, most hub motors constitute a wheel integrity problem in their own right. You are absolutely right about thick spokes, though. They don't work for bicycle rims; they are a childish approach to the problem of spoke breakage and the recourse of trashy manufacturers.

I use spokes as thin as 17ga (1.5mm) on my own bikes. They are a nuisance to build with because they wind up so much, but they make very reliable wheels.

I think 14ga spokes are the best for a beginner to learn wheelbuilding, and 14/15ga butted spokes are the best default choice for most wheels most of the time.

Chalo

 

[johnrobholmes]

I certainly agree that a thinner, higher quality spoke is the best ticket. 13/14 butted is my general recommendation for 99% of ebike wheels with bicycle rims because of the flange hole size, although sometimes 12ga has to be used. There just isn't any secure (and cheap) way to washer up a 3.5mm hole for 13 or 14ga spokes that I have found. I wish that the angle of entry into the rim would allow for 14/15 without breaking the spoke at the thread. I have thought heavily about getting some cone washers to allow for angle drilling of non eyeleted rims to help remedy this. Anybodies thoughts on this?


For moped rimmed wheels the 11/12 butted, 12ga, and 13ga are a good match to the rim and flange strength. Typically on the gas mopeds we will use 12ga on the rear and 13ga on the front unless the rider is over 225lbs/ 100kilos.


The failures I see on my own builds are because of the rim insertion angle, breaking at the threads. There seems to be a trend of about 1000 miles needed to get to this point with high quality spokes. This is an obvious sign that we need to address this angle with a specialized rim or washer to allow for a better insertion. My concern with a washer is that it will want to slide on the rim because of the off angle tension, so my gut reaction is that a specialized dimpled rim should be made. We can't do dimpling with double wall, but we could have boxed in corners at least. It aint cheap for an extrusion though.

 

[neptronix]

Really. Here i've been chasing my tail calling up specialty bike shops, starting new threads asking about spokes, wheel building, and strength in a hi-power chain driven application, even sent a PM to Luke, but only here in a question thread from a newer member, do i get my answer.

Hey amberwolf, reset my post count to 0... :lol:

 

[liveforphysics]

Recommending thicker spokes would be similar to someone asking what they can do about their frequent crashes always breaking their arms, and someone recommends putting titanium rods through their arm bones. The problem is not with the arms (in 99% of cases at least), the problem is in whatever is causing frequent crashes and still trying to catch yourself with your arms.

 

[Kingfish]

The function of spokes is to provide a modicum of suspension, combined with the rim and tire. It’s a complete lightweight system that works up until the point where a good solid jolt causes the material to fail (the spoke), and it should happen long before the rim will fail and taco.

When we purchase a complete bike, moped or motorcycle, the entire system is properly weighted and calculated so that spokes and rims work flawlessly together – short of entering into a Seattle pothole – to which there is possibly no escape! Though at least the experience is not as bad as a Florida sinkhole… just yet.

However, employing hub motors changes the equation considerably: We’re adding quite a bit more mass, and therefore adding resistance to moments of inertia which leads to greater stress upon the rim and spoke system. Spokes are the easiest to upgrade, followed by good strong rims.
If most of us rode at 20 or 25 mph, we could probably get away for a short while using the stock rim setup, but the problem is that we are either adding the motor ourselves, or purchasing an integrated motor and rim. I can guarantee that if it is the latter, the engineering has already been applied and that the rim is double-walled with good solid spokes, probably 13-gauge – at least, I’m pretty dang certain my 9C rims from ebikes.ca are 13-gauge.

Checking their website; the Hub Motors page states:

“I am a big guy, should I worry about spokes breaking?”

“Possibly. Crystalyte 13 gauge spokes were notorious for fatigue failing after several months of use, and this was much more prominent with heavy riders. At the time, we generally recommended that those concerned with spokes failing have their wheels re-laced either using DT, Wheelsmith, or Phil Wood spokes. These brand name spokes either in 13 or 14 gauge would work great, but unfortunately the wheel relacing and custom spoke sets added significant cost to the wheel. In late 2008 we decided to have all of our Crystalyte motors come with thick 12 gauge Crystalyte spokes. These large spokes don't generally break, but the non-standard gauge adds its own complications. The nipples won't fit through the eyelets of standard rims, replacement spokes are difficult to source, and your handy bicycle spoke wrench probably won't have a 12 gauge size for tensioning/truing the wheel.

“The Nine Continent wheels are built using regular 13 gauge Chinese spokes, and it is too early to say if they will be prone to spoke failures down the road or not. “

OK, so there you have it: Rims with hub motors are at least 13 gauge, if not 12 gauge. Using a lighter gauge with hub motors is unsafe. I can personally attest to that. :wink:

If I’m building a moped or motor-driven cycle or motorcycle, I will want to use the best spoke possible, and I won’t shy away from beefy.

The flipside of going with a very strong spoke is that the flexibility of the rim will decrease; this is when we need to employ a good frame and fork suspension system to take up for this reduction. But I think that is a good subject for another topic.

~KF

 

[neptronix]

Here's something to consider, in terms of hub motors.
Your spoke flanges are about oh, i dunno, 3-10 times taller than a regular bicycle hub :lol: thus, they are drastically shorter.

Imagine standing at the end of a 10ft long bar of steel, how much it would flex and sag underneath your weight.
Now cut that bar of steel into 1/3rd of the size and stand on the end. Prolly doesn't flex too much, does it?

I think that 14 gauge spokes are good for hub motors. Now as far as building a high power disc-brake driven chain drive wheel, i start to feel a little more skeptical at that point

 

[johnrobholmes]

I feel the other way, I feel more certain in the spokes ability when it is longer and not attached to a huge hub motor. It has more stretch and give. A high power bike can have 14ga spokes and Luke has proven it.

 

[liveforphysics]

The function of spokes is to provide a modicum of suspension, combined with the rim and tire. It’s a complete lightweight system that works up until the point where a good solid jolt causes the material to fail (the spoke), and it should happen long before the rim will fail and taco.

Radically incorrect. You could think of the rim like a flexy noodle, or like a stone arch with no cement. It's rigidity alone is relatively nothing compared to the loads, in fact, you can just grab a mt.bike rim and try to sit on it and it just collapses under your weight like a pile of goo.

The only way the system works is the stress from the spokes pulling inward. In the same example, you try to sit on the laced wheel, and it could perhaps support 20 of yourself rather than collapsing under some small fraction of your weight alone. This is because the spokes create a system of stress distribution over a wide area of the wheel, enabling the forces to be shared over the whole perimeter.

To have this function work, the spokes MUST all be high in the elastic region of the strain/stress curve, this allows the compliance in the wheel without causing spokes to become unloaded.

A bicycle rim can not put a large diameter spoke into this stress zone, the rim itself collapses (I've tried a few different good eye-lit rims, there is a reason motorcycle rims are about 5x thicker).

Say you set the same ~100lbs of tension on a thick spoke wheel as a thin spoke wheel. Now you load the wheel. The moment event the most tiny bit of deformation occurs, the thick spoke wheel has huge patches of spokes completely unloaded, because they are so low on the material strain curve, that even 0.01mm (or whatever) of compression distance can drop the 100lbs tension to 0lbs, now it can't distribute it's strength through the perimeter of the rim, and it's going to fail from the stress risers that get created in the places that are carrying the stress. You put the same load on the rim with thinner spokes high in the stress curve, and hey! No problem, you have substantial deformation distance you can travel while still staying in tension and functioning to distribute load. The distributed load doesn't create the stress risers that cause failures.

The thicker spoke wheel would be stronger if you could put it in the same part of the stress curve, but for thicker spokes, that can be ~400-900lbs of tension required to achieve it, and bicycle rims simply buckle or pull nipples through at those tensions. Hence why if you have a motorcycle rim you should go for bigger spokes, as they can handle 400-900lbs of load per spoke, putting it in the proper range of the strain/stress curve, and allowing the wheel to distribute loads.

OK, so there you have it: Rims with hub motors are at least 13 gauge, if not 12 gauge. Using a lighter gauge with hub motors is unsafe. I can personally attest to that. :wink:

Wrong. See above.

 

[Kin]

Sooo, LFP,
Conceptually, I think what you're saying might make sense. But maybe that is just because it's easy to listen and accept.

Maybe I could ask a few questions to clarify what you're saying. One, is the way you say "high in the elastic region." But, I'm not quite sure what you mean by that, assuming you're talking about the linear portion of http://en.wikipedia.org/wiki/File:Stress_v_strain_A36_2.svg.

As long as the spokes are under some tension, I think they should be distributing loads over the elastic region. A rod with twice the cross sectional area, but half the strain, I *think* should be causing the same tension, within that linear elastic region.

What makes sense to me, is that if I am putting the spokes under more tension without plastic-ally deforming them, then the rim should be even more resistant to deformation.

I *think* what you're saying is that a thicker spoke might be under so little strain that the slight deformation from the load is liable to compress it enough that it's no longer tensile, and then it's trying to actually bear the load in compression, and then that's how it breaks. Is this what you're describing? Because, otherwise, I don't quite see why a thicker spoke with less strain might not deliver the same tensile pull on the rim. I can see how they're no benefit to a thicker spoke, though, because the whole business is not really about compression.

____________
-Does my writing make any sense? Or am I just thinking out loud? I'm not totally sure.

 

[Ypedal]

I lack the vocabulary to express myeself correctly.. but here goes with personal experience.

Chalo gave me a lead on a stash of rims Zero MX used on early versions of the dirt-bike prototype phase, they are 20" rims, with eyelets, no-brand-name but serious rims for a bicycle grade rim.. the eyelets are 14g but having a stash of 12g cheap chinese spokes on hand i used what i had available.

result, a heavy hub motor, with flange drilled for 12g spokes, in a 20" rim, i used a round file to ream out the eyelets to accept 12g spokes and had to go radial lace ( already had spokes... no choice ) but since this rim is so massive i was able to crank those 12g spokes down to the point of the crappy nipples almost stripping with a park tools unit tight fitting to the spoke ( had to dremel it to fit ) no way to hand stress and strech the spokes i had to let the wheel sit overnight and re-tension over 2 days until all 36 spokes were quitar pitch tight ( 440 ? ) ..

I've built a bunch of these wheels ( regular rims would just buckle, or pull the nipple thru ) and they stood the test of time and abuse.. this is more a motorcycle wheel than a bicycle wheel...

with a hub flange drilled the proper size, and a solid rim, 14g would certainly be more than enough for 99% of our needs.. unfortunately.. much of the parts available to us are not made to go together.

** ( and yeah.. i've managed to break one, it took one hell of a hit to do it.. !~!!!!! )

http://www.youtube.com/watch?v=z2YhUHMdY2M

[youtube]z2YhUHMdY2M[/youtube]

 

[liveforphysics]

I *think* what you're saying is that a thicker spoke might be under so little strain that the slight deformation from the load is liable to compress it enough that it's no longer tensile, and then it's trying to actually bear the load in compression, and then that's how it breaks.

Yes! This is exactly it. Your displacement range while staying under tension is critical, as things WILL deform under stresses. The trick to a strong wheel is to have a wheel built that still shares load when it deforms, this requires having substantial stretch in the spokes (aka, getting them high up in the elastic strain curve).

Wheels made from thick spokes at the same rim limited starting tension instantly have about 3/4 of the spokes sag loose the moment the wheel deforms a tiny bit, a wheel with the same rim limited starting tension made from thin spokes still distributes stress through all the spokes when the rim deforms. This is how they hold up, and why big thick spokes in bicycle rims are least durable.

 

[liveforphysics]

I remember having a debate with Chalo about this years ago. He kept telling the tension needed to be at some extremely high point on the spoke for the wheel to last. I was looking at the tensile strength for various spoke materials, and showing him that with that cross section and these tensions, you were about 90% of the way to the yield point of the steel with the wheel just sitting there unloaded, and I told him he was nuts, and that he was using up 90% of the strength of the spokes with the wheel just sitting unloaded.

After my own ideas sucked, I tried his, and the wheel was bullet proof. Little 14 or 15awg Sapiam spokes stretched right up to the point of yielding, so they were dead on the transition out of the elastic zone. That wheel not only didn't break anymore, but it also stayed extremely true through massive abuse.

The reason was, it was able to distribute stress over a wide area, even with some deformation. That is impossible to achieve with thick spokes.

 

[Farfle]

This is why bmx wheels and cargo bike wheels have a higher spoke count of the same gauge spoke. More evenly distributed tension makes a stronger wheel.