SPOKES

[mike killay]

Yet again, I have had to replace a broken spoke, again broken at the 'J' bend.
So, I feel that it is time to debate modern spokes.
I rode bikes throughout the 1950s, then motorised bikes for few years and then motor cycles.
Later, in 1986 I again began cycling, using a 'Universal' made bike that had old fashioned steel rims and spokes. I rode this bike for 20 years.
I cannot remember either myself or my friends ever having a broken spoke.
So,
Why do modern spokes break so much?
In separate threads, Trex has posted that loose spokes might break if the ferrule catches in the rim.
I contend that loose spokes do not break, it is the spokes either side of them carrying greater weight.
BUT
d8veh has posted that he has had success using thinner spokes. He claims that thinner spokes are more able to flex under compression.
I however contend that spokes are never under compression. The ferrules are in holes and you cannot push against a hole. My contention is that all the weight is carried by the axle hanging from the upper spokes.
(In twin wall wheels the spoke ferrules do not even touch the inner tube).
SO,
Could the problem be,
either alloy rims behave differently to the older steel rims.
OR
Modern spokes are badly made. (perhaps something as simple as heat treatment after the 'J' is bent)
I do not know anything about spoke manufacture but I do contend that we have a problem that was not known years ago.
I would love to hear your thoughts.

 

[KTM Bike Industries UK]

What brand of spoke are you using? They are not all created equally.

 

[Deleted member 4366]

d8veh has posted that he has had success using thinner spokes. He claims that thinner spokes are more able to flex under compression.
I however contend that spokes are never under compression.

I probably didn't explain it well. I meant that the bottom part of the wheel is in compression, not the individual spokes. My theory is that the greater elasticity of the thinner spokes, spreads the loads around more evenly so that the spokes are not subjected to such large changing forces. Also, with thick spokes, the difference between tension and loose is about half a turn on the nipple, so it's much easier for thick spokes to go loose where the wheel is in compression.

 

[danielrlee]

Hot-rodders running huge power through hub motors will confirm, that although somewhat counter-intuitive, thinner spokes will generally give a stronger wheel. Many a power junkie has battled with braking spokes and discovered the solution is to simply swap their spokes for thinner ones.

 

[mike killay]

Thinner spokes are intriguing. Although counter intuitive, if experience shows that they work, well I am all for it.
But why do modern spokes break?
If you Google 'Broken spoke' it appears that all the world are up in arms about this problem.
I quoted my cycling history, but since the invention of the safety bicycle, whole armies have moved around on bikes without apparently having this problem.
Is it a modern problem, is it simply poor manufacturing or something else?
KTM asks what brand of spoke, but all that I know is that they came with the bike (Chinese made)
Does this hint that spoke manufacture is a dark art not practised by the Chinese?

 

[danielrlee]

For the purpose of full disclosure, I don't have any practical experience with breaking spokes - I only weigh a little over 9 stone and don't currently run more than 3Kw through a hub motor. My knowledge is purely theoretical and is based on others' experiences.

I'm going to backtrack ever so slightly here. Thinner spokes don't necessarily give a 'stronger' wheel per se, but they are better at dealing with the types of forces that a hub motor exerts on a wheel.

I might have missed this previously, but what type of drive system are you dealing with here?

 

[trex]

No, they break because of the combination of the rear spokes and rear geared hub motor. Any other combinations (CD or rear DD) won't normally break spokes. This is because rear hub drive has higher traction, hitting the spokes with the full torque force of the geared hub. At peak, the rear hub gives out more than 5 times what a normal cyclist can output. There is also the issue of standing waves. The heads of the spokes are where the antinodes of the standing waves are, they can vibrate and break if they are loosened.

 

[anotherkiwi]

I don't think DT Swiss supply spokes to Chinese hub motor manufacturers... I may be wrong.

The problem with thin spokes on hub motors is the bigger holes they have to cater for larger gauge spokes and that can me excessive play at the hub.

 

[mike killay]

Trex's point about vibration brings in a new parameter. I had not considered that.
But, would returning to steel wheels improve the situation?
Are alloy wheels too hard?
I have broken rear spokes on a hub motor and a central drive motor.
What is the experience of cycle racing? Do they break spokes?
But why didn't my Cyclemaster 25cc engine (Hub drive) break spokes?

 

[KTM Bike Industries UK]

you're just not using good enough spokes.
Get some DT or Sapim double butted and you can then if your spokes break its the rim, hub or wheel buiders fault.. not the spoke.

 

[mike killay]

you're just not using good enough spokes.
Get some DT or Sapim double butted and you can then if your spokes break its the rim, hub or wheel buiders fault.. not the spoke.

So are you of the point of view that all the spoke problems are down to poorly manufactured ones?

 

[JuicyBike]

Modern disk brakes introduce a completely different route for the transfer of braking force from road surface to bike frame, compared to rim brakes. Spokes are under greater stress when using disk brakes than rim.

 

[KTM Bike Industries UK]

So are you of the point of view that all the spoke problems are down to poorly manufactured ones?

as I've said if you buy good ones, it pretty much rules out the spoke being the cause of the problem. If you're then still breaking spokes, there are 3 other things that can cause it.

But having raced DH at World Cup level and built wheels for myself and our whole team, plus when I had a "proper" job I used to wheel build for the likes of Leisure Lakes I do have some experience of abusing wheels. The guy who taught me went onto be top mechanic at British Cycling. I can say that double butted spokes should not be breaking.

You can do crazy things to the wheel and the spokes suck it up.

 

[trex]

I don't think poor quality steel is the reason. A 13 gauge spoke can easily take 200kgs of pulling power on its own. It's the wheel truing that matters. If all your spokes are tightened to the same tension, your rim will spread the load best and deform the least and none of your spokes will 'ring'. Spokes work when they are pulled and must not be put in a situation where they are compressed so try this: get someone to sit on the bike and ping the spokes nearest to the ground (6 o'clock) then those at 3 o'clock and 9 o'clock. You will want them to ping as same to one another as possible.

 

[KTM Bike Industries UK]

I don't think poor quality steel is the reason. A 13 gauge spoke can easily take 200kgs of pulling power on its own. It's the wheel truing that matters. If all your spokes are tightened to the same tension, your rim will spread the load best and deform the least and none of your spokes will 'ring'. Spokes work when they are pulled and must not be put in a situation where they are compressed so try this: get someone to sit on the bike and ping the spokes nearest to the ground (6 o'clock) then those at 3 o'clock and 9 o'clock. You will want them to ping as same to one another as possible.

how many wheels have you built Trex?

Honestly double butted spokes are the best, they give more.

There are loads of things that make spokes break. Black ones for instance are a bit more brittle so snap near the threads at the top.

Cheapo hubs cause problems because the holes in the flange of the hub aren't rounded off enough so they can cut into the shoulder of the spoke.

But if you're snapping spokes on a bike there are a number of things to look at but, cheap spokes snap. Its to to do with the process of bending them at the shoulder, as much as they are often built badly into cheap hubs.

 

[awol]

If the J-end isn't sat properly in the hub hole this could place pressure on the bend and cause a break.
Graham at Tiller Cycles recommended to me to use brass spoke washers a couple years ago and seems to have helped me.
http://www.tillercycles.co.uk/page2.html
Also Sheldon Brown mentions them
http://sheldonbrown.com/wheelbuild.html#washers

 

[EddiePJ]

I don't think poor quality steel is the reason. A 13 gauge spoke can easily take 200kgs of pulling power on its own. It's the wheel truing that matters. If all your spokes are tightened to the same tension, your rim will spread the load best and deform the least and none of your spokes will 'ring'. Spokes work when they are pulled and must not be put in a situation where they are compressed so try this: get someone to sit on the bike and ping the spokes nearest to the ground (6 o'clock) then those at 3 o'clock and 9 o'clock. You will want them to ping as same to one another as possible.

My tried and tested preferred method is to simply give my wheel set to a friend on a regular basis and get him to check them using one of these. https://www.dtswiss.com/Resources/Support/PROLINE/DT-Swiss-Proline-Tensio-User-Manual-en

Other than the very occasional truing after a hard knock, my Swiss DT rims have always remained perfect.

My take on it is that regular maintenance and professional care count for a great deal.

 

[DouglasXK]

I have shamelessly copied this off the Broken Spoke Bike Co-op.

The ingredients of a bicycle wheel:

• 
  1x rim – a narrow metal trough drilled with typically 32 holes and bent into a hoop
  
  1x hub – a sleeve of metal with 32 holes cut into a flange at either end and a spinning metal rod held within
  
  32x spokes – lengths of wire threaded at one end and with a 90 degree corner and a head like a nail at the other
  
  32x spoke nipples – small threaded beads that screw onto the threaded end of the spokes

The lacing together and tuning of these components is both a complex activity and a skill professional bicycle mechanics pride themselves on. That said, the majority of wheels doing the rounds in Oxford are machine built, machine tuned and cheaper than the hand-built wheel. Unfortunately, they are also inferior.

Machine built bicycle wheels lack the intuitive holistic construction of their hand-built counterparts. Among other things, the spokes are often twisted and weakened by the tightening process, the rim is thin with minimal reinforcement and the hub is made of flexible steel rather than stiffer aluminium. Practically speaking, repeated introduction of a machine built wheel to the patchy road outside the Old Music Hall (on Cowley Road), the crumbling manhole covers at the bottom of the High Street (travelling westbound), or the disfigured surface just before the roundabout at the top of Woodstock Road, and you’re going to find that said wheel is going to become warped, rattly and reluctant.

Have you ever thought about what happens when your bike drops into one of these treacherous chasms? The impact from the pothole travels from road to rider through the tyre and rim at the bottom of the wheel and then into the spokes. The jolt will then be passed into the hub and up through the fork to the handlebars.

But do you know where the shock is absorbed? Unless you have a suspension fork or an under-inflated tyre, the spokes at the area of the wheel that hits the ground are where a lot of the shock from the impact is reduced. Their tension reduces considerably. As the wheel continues to spin, this reduction in spoke tension is passed onto the next spokes along, when it’s their turn to be at the bottom of the wheel. But once a spoke has passed the bottom of the wheel, it returns to its original tension. The better built the wheel is, the more times these spokes can relax and spring back without impairing the wheel’s roundness.

This flexibility in tension is a big part of why cycling is so popular. It was only when the rigid wooden wheels of the bone-shaker bicycles of old were replaced with wire wheels, that cycling started becoming a more mainstream, everyday activity.

So next time you cleanly bounce over that not-very-lowered-curb on Turl Street, perhaps spare a thought for what’s going on with those spinning bits between you and the road!

 

[Deleted member 4366]

I don't think the type of spoke matters much. I only use the cheapest, and I've never had a problem even though I'm heavy and nearly always over-power my motors. I'm not a good wheel-builder either.

One plausible theory that I read, said that it was down to the length of the elbow. Most of my builds have had too short elbows, which meant that I had to bend the spokes at the hub flange to point at the rim. The result is a prelonged curve around the flange, which will suffer a lot less stress than the normal sharp right-angled bend.

 

[mike killay]

I suspect that it is the bend that gives the trouble.
I do wonder if the older spokes had a slightly different shape at the bend, or received stress relieving treatment after being bent.
It really doesn't matter about some of the explanations given here.
I contend that modern spokes are prone to snapping, older spokes were not.
If this is the case, why aren't manufacturers doing something about it?