Breaking Spokes

Joined
Feb 28, 2008
Messages
67
Location
The Beach, CA
I have a rear MAC 6T motor and recently I started breaking spokes. Driving it with a 36V Ping battery, it wasn't due to torque but actually happened twice when braking down a hill (caliper brakes not disc). All 3 spokes broke in the center, not by the hub or rim. I have a couple of questions.

  • 1) What gauge spokes do I replace them with so this won't happen again?
    2) Any idea what length spoke I need?
    3) Any suggestions for good places to order a replacement?
    4) If this happened while braking, is there something I'm doing wrong?

Thanks for any help!
Peter
 
Breaking in the middle is caused by them being loose. It can also happen easier if they are too thick, and/or of cheap quality, but all lose spokes will break eventualy.

You avoid that by keeping the spokes properly tensioned. If they are lose, they are going to break.

As for the right size, it's impossible to say without knowing what your rim's ERD is. Every rim is different, so you would have to measure.

Also, the spoke gauge can vary by the vendor. It could be anything from 16g to 12g. But likely its 13 gauge.

The best thing to do is take off a non-broken spoke and head for your local bike shop. They can measure the spoke and cut you a replacement.
 
I've never broke one on the front motor wheel. Rear, much different story. One pluck, followed by a couple more kabloops and scalabadoodle sounds, and by the time I stop it looks like a bowl of spaghetti back there and the rim is ruined. So I just slap a new rim on and hope it outlasts the previous ones. :x Sometimes they are triggered into failing by a sudden flat tire. :twisted:
 
Drunkskunk said:
Breaking in the middle is caused by them being loose. It can also happen easier if they are too thick, and/or of cheap quality, but all lose spokes will break eventualy.
You avoid that by keeping the spokes properly tensioned. If they are lose, they are going to break.

Too loose? I would've thought it would be the opposite that would cause that. The bummer thing is that I just had the wheel checked and trued a few weeks ago.

Drunkskunk said:
As for the right size, it's impossible to say without knowing what your rim's ERD is. Every rim is different, so you would have to measure.
Also, the spoke gauge can vary by the vendor. It could be anything from 16g to 12g. But likely its 13 gauge.
The best thing to do is take off a non-broken spoke and head for your local bike shop. They can measure the spoke and cut you a replacement.

You made me have to look up what ERD means. :D I found that it's 536 on this rim but I'm sure someone might even recommend replacing a rim if I had to ride on it, possibly compromising its integrity. Thanks for the info!
 
The fingers said:
I've never broke one on the front motor wheel. Rear, much different story. One pluck, followed by a couple more kabloops and scalabadoodle sounds, and by the time I stop it looks like a bowl of spaghetti back there and the rim is ruined. So I just slap a new rim on and hope it outlasts the previous ones. :x Sometimes they are triggered into failing by a sudden flat tire. :twisted:

This is the first time I've broken a spoke and 2 times in a week. On my front hub motor, I never broke a spoke even though I abused it way more than my current rear motor. I heard a ping noise and then my back wheel starts to rub on the brake pads. I made it home the first time but the second time after repair I broke 3! Couldn't ride home that time. I'm going to be paranoid about braking spokes for a long time now. :?
 
When people have suffered broken spokes it makes me wonder whether the wheel was built correctly. When I started building my own wheels I followed Sheldon Browns guide;

http://www.sheldonbrown.com/wheelbuild.html

The final stages of seating and stress relieving are very important. When the wheel has been laced and initially trued do people stop there thinking it is done? time wise this is at about a 1/3 of the time it actually takes to complete the job properly. Hammering the spokes down on the hub flange, re-tension and true the wheel, then stress relieve where they are laced to achieve and angle change not a bow then re-tension and true again. It all takes time but builds a stronger wheel far less prone to suffer spoke breakages. Washers if needed under the spoke heads at the hub flange are also very important to ensure the bend is snug up to the flange face.

I have seen lots of examples of wheels with bowed spokes that have not been stress relieved, the spokes will become looser with use, then as the load is then not shared amongst all the spokes failures will happen. It takes more time to build a good wheel but it is worth the effort.
 
I remember popping spokes when we used to use the heavy SLA battery packs. You don't notice the spokes coming lose but sometimes hear a noise. Reducing the weight of the bike will help with the lose/popping spoke issue.
 
Starts me wondering what the tuner did. How bent up was it when you took it in?

I've never seen a spoke break in the middle. Always at the nipple or the bend at the other end.
 
Short of using moto/scooter rims and spokes I seriously doubt bicycle rims/spokes will ever survive when using large diameter hub motors.

I'm a firm believer in "thinner is better" but so far I've never managed more than 15k miles from one of my rear wheel motor builds. Gone through some spokes but I've never had one break in the middle or at the nipple, yet.

I dunno what to advise for reworking your wheel in shop but when you're out on the road and spokes start to break - it's time to be prepared with spare "universal" length spokes:


Scavenge full length spokes from used wheels and keep 'em handy along with a spoke wrench. I always have leatherman pliers and it only takes about 5 min to twist an emergency spoke up to tension.
 
PetersReviews said:
Drunkskunk said:
Breaking in the middle is caused by them being loose. It can also happen easier if they are too thick, and/or of cheap quality, but all lose spokes will break eventualy.
You avoid that by keeping the spokes properly tensioned. If they are lose, they are going to break.

Too loose? I would've thought it would be the opposite that would cause that. The bummer thing is that I just had the wheel checked and trued a few weeks ago.

Drunkskunk said:
As for the right size, it's impossible to say without knowing what your rim's ERD is. Every rim is different, so you would have to measure.
Also, the spoke gauge can vary by the vendor. It could be anything from 16g to 12g. But likely its 13 gauge.
The best thing to do is take off a non-broken spoke and head for your local bike shop. They can measure the spoke and cut you a replacement.

You made me have to look up what ERD means. :D I found that it's 536 on this rim but I'm sure someone might even recommend replacing a rim if I had to ride on it, possibly compromising its integrity. Thanks for the info!


The reason it is opposite to your intuition is that wheels are constructed against normal intuition. Spokes are tension devices and only work when in tension. Your spokes don't hold the wheel up from the bottom. The spokes all pull the wheel tight with all spokes carrying some of the load, with no spokes ever carrying all of the load at any one time. Otherwise the individual spokes would have to be ridiculously strong in compression.


To get proper spokes for replacement, take the broken spoke out of the wheel and measure it with a ruler. Measure it from the start of the bend to the threaded end.

If just replacing one spoke, order the same gauge. But if you have the time and patience, replacing all spokes with 14/15G butted spokes will give you MANY maintenance- and worry-free miles.

To give you an example, my 700c rim built by E-bikekit with 12G spokes was busting spokes every hundred miles. Super annoying, to say the least, when your round trip commute is 25+ miles in a day.

With the 14/15G spoked motors, my wife and my own bikes have covered nearly a thousand miles without ANY need true or adjust or worry or even think about wheel integrity.

(And my bike goes 40mph)
 
I recently had 2 broken spokes, next to each other, that snapped on the bend at the hub end. Looking at the nut end both were at the end of the threads, I don't think they were over tightened but I guess it's always a possibility. I got replacements that were a couple of mm shorter after measuring the length needed. The laced motor came from Crystalyte Europe and their range of spoke lengths had gaps missing out the measured length I needed so I guess they just laced from the sizes they stocked.

Just in case anyone wants 12, 13 or 14g stainless steel spokes in exact mm lengths I got them from Green Motion. They even emailed tables showing sizes when I asked-even nipple sizes (I recall some posts here of the wrong sized being sent by a different supplier). Delivery was quick, and they were exactly as ordered. The listing was for 36 spokes but they quickly sorted out the quantity I wanted.
 
As others said, it's counter intuitive to the layman, but over tightening won't break the spoke.

A 14 gauge Sapim is rated for 1250newton meters. That's ~920 lbs per spoke. You will break the hub, strip the nipple, and crack the wheel long before you break the spoke from over tightening.

The reason they break from being lose is metal fatigue. A spoked wheel is designed to share the load over all the spokes. but when they are lose, individual spokes have to share a greater portion of the load, and they have to stretch further to make up for the slack in the other spokes. So the spokes go from being stretched to relaxed, over and over again. Eventually, it develops tiny cracks and fails.
 
I'm 270 lbs and haven't broken a spoke in well over a year and 5K miles after replacing really crappy spokes with these really cheap spokes.
http://www.ebay.com/itm/Primo-166mm-Stainless-Steel-Forged-12g-Spokes-w-nipples-100-/290613208288
 
wesnewell said:
I'm 270 lbs and haven't broken a spoke in well over a year and 5K miles after replacing really crappy spokes with these really cheap spokes.
http://www.ebay.com/itm/Primo-166mm-Stainless-Steel-Forged-12g-Spokes-w-nipples-100-/290613208288

I can vouch for the Primo spokes as well. Basically all branded stainless steel spokes should be fine as long as the build is done well. Equal tension and stress relief are crucial, as is spoke/rim angle - if this gets too slack, they start to break at the nipple. The bend at spoke shoulder needs to be supported by hub flange. To achieve this, you need to insert a 2.5mm ID shim thru the spoke shoulder.
 
meh i hate bicycle wheels - their frigging pain and totally unreliable it's always the wheels that have issues
not much you can do but invest in quality parts and maintain/true it - but after a while you get tired of it- as its time consuming
building it properly also seems like a skillset
this is something you never have to deal with on scooters/motorcycles or cars- wish they made these hubs in mag wheel format or simply solid like you see on some motorbikes- i think golden motors has a small 20" mag wheel but all the others are spoked- its funny though that my gm 26" is spoked with 12ga and many will tell you not to use 12ga spokes - i never had issues with this hub, it was always the cheap chinese 13ga hubs that broke. but im rebuilding that wheel with quality rim 13-14 butted components so we'll see- some have had success for many miles with good parts/maintenance. if i still have issues ill prolly switch to a e-scooter or find a bike frame for a 20"

MagicPie 20in.jpg
wish they made this in 24 or 26"
 
I've broken a couple of spokes in my Chinese-laced wheel. Both times from hitting a sharp bump at speed (last one was a 1.5£ step at 30mph). Broke at the nipple both times.

I've given up on the wheel. When it gets really bad I'll do what others have suggested and learn how to rebuild it properly with thinner, quality spokes. I imagine it will be a long and frustrating process but hopefully worthwhile.
 
FWIW, I have never ever broken a spoke since I went to full suspension bikes. Even when I taco folded a rim, no broken spokes.

But many have said this over and over, get quality spokes and they don't need to be fat.

I'm still perplexed about the broken in the center thing. I've always just seen bent in the middle, never snapped. Broke I see them at the bend, or the start of the threads.
 
Tench said:
When people have suffered broken spokes it makes me wonder whether the wheel was built correctly. When I started building my own wheels I followed Sheldon Browns guide;

http://www.sheldonbrown.com/wheelbuild.html

That's a great guide! I learned a lot. I'll bet most people don't build wheels correctly!
 
lester12483 said:
I remember popping spokes when we used to use the heavy SLA battery packs. You don't notice the spokes coming lose but sometimes hear a noise. Reducing the weight of the bike will help with the lose/popping spoke issue.

I use a Ping 36V which is a fraction of the weight of my old SLA batteries and I'm not a heavy rider. I'm now wondering if these are just bad spokes. All 3 broke in the middle!

dogman said:
Starts me wondering what the tuner did. How bent up was it when you took it in?
I've never seen a spoke break in the middle. Always at the nipple or the bend at the other end.

I don't think the guy at the bike shop is at fault. 2 more spokes broke after the first one and all 3 in the middle! The wheel wasn't that far out of true (if that's the right terminology).

Ykick said:
Scavenge full length spokes from used wheels and keep 'em handy along with a spoke wrench. I always have leatherman pliers and it only takes about 5 min to twist an emergency spoke up to tension.

Good advice! I'm always going to carry extra spokes with me from now on!

cal3thousand said:
The reason it is opposite to your intuition is that wheels are constructed against normal intuition. Spokes are tension devices and only work when in tension. Your spokes don't hold the wheel up from the bottom. The spokes all pull the wheel tight with all spokes carrying some of the load, with no spokes ever carrying all of the load at any one time. Otherwise the individual spokes would have to be ridiculously strong in compression.

Makes sense! I love this forum because even after all these years of riding, I'm always learning something new!

dogman said:
I'm still perplexed about the broken in the center thing. I've always just seen bent in the middle, never snapped. Broke I see them at the bend, or the start of the threads.

I know! All 3! Here's a picture of the last 2 broken. I think Drunkskunk is correct in them probably being too loose and metal fatigue slowly weakening them.

i7fBuvbl.jpg
 
That is the damnedest thing I've seen in a while! You felt them break while riding? If I didn't know better I might also consider vandalism? Somebody mad at you? LOL...

Probably just crap metal if not very poor tension/true? Thanks for the replies and pic.
 
Ykick said:
That is the damnedest thing I've seen in a while! You felt them break while riding? If I didn't know better I might also consider vandalism? Somebody mad at you? LOL...

Probably just crap metal if not very poor tension/true? Thanks for the replies and pic.

I heard them pop! One and then the other! Probably a combination of bad spokes and low tension.
 
There have been times when poorly manufactured spokes have reached the market, but I bet manufacturers try to keep it quiet. I did a google search a few years ago got that got a few hits after a friend had a similar problem.
 
alsmith said:
There have been times when poorly manufactured spokes have reached the market, but I bet manufacturers try to keep it quiet. I did a google search a few years ago got that got a few hits after a friend had a similar problem.

actually come to think- last year i also broke a spoke - and it broke just like yours- it was from a chinese 9c hub motor- 13g.
it was a brand new wheel alot of click click clicks when i first started riding it(probably due to not being tensioed correctly or breakin period)- than i got it trued- same deal- eventually i busted a spoke.
spokes should not break like that so i think they just made a a defective batch of spokes made and we got them....its just better to buy the bare motor and take it to bike shop to built it up from scratch
 
Are you sure the wheel is built properly? It looks like you have a 3 cross with the incorrect pass over causing breakage not randomly in the middle, but at the cross point where is is rubbing and loading. Were you oiling them properly?

Another cause of breakages in the middle would be butted spokes. They are at their thinnest in the middle.

I suspect it is wrongly built. It looks a lot like 3 cross on a hub motor, which rings alarm bells straight away.
 
friendly1uk said:
Are you sure the wheel is built properly? It looks like you have a 3 cross with the incorrect pass over causing breakage not randomly in the middle, but at the cross point where is is rubbing and loading. Were you oiling them properly?

Another cause of breakages in the middle would be butted spokes. They are at their thinnest in the middle.

I suspect it is wrongly built. It looks a lot like 3 cross on a hub motor, which rings alarm bells straight away.

I think it is just the angle that the picture has been taken at is fooling you, my single cross 5300 looks like that if you look at the far side of the wheel from a bit of an angle.
 
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