Cycling UK Forum

"The vast majority of spokes that have broken for me are those that snap while trying to adjust them"


That's the norm when someone brings me an old bike to true the wheels on - the other sound is the "thunk" - my heart hitting the floor as it sinks.

I've been following this thread with interest, especially the latter half.

As you may know, I've built a few sets over the last couple of years, I'm definitely no expert, but I'm good with my hands and have an innate "feel" for things. The wheels I've built have only been done with a spoke key, nowt else. I don't worry unduly about tension, so long as the wheel is true and the spokes feel tight and they all ping the same note - what the heck!

I've only ever had one spoke break in my entire cycling life. Actually not true, I did break a few when I was a lad, trying to true up my old wheels with rustless spokes - nipples seized solid and I twisted the spokes into submission!

The only SS spoke that broke was on a pair of wheels from Ribble - Mavic MA3/Campag Mirage 32/32. The breakage was on the drive side rear, and it went "snap" whilst rounding a RH corner a little too fast whilst braking, and with a heavy trailer in tow.

It was that breakage that set me straight - Build Your Own - you know it's right then!

"I don't worry unduly about tension, so long as the wheel is true and the spokes feel tight and they all ping the same note"

If they ping the same note then the tensions must be pretty close.

"The wheels I've built have only been done with a spoke key"

What else would there be? Unless you mean no jig - I built my first few on a bike using the brake as a guide. A jig is a very nice luxury!


Build Yer Own - I'm right with you there! Even if a professional wheelbuilder is statistically better than you, they have quotas and profits to think about, you don't - plus you're the sorry mug who's going to ride the thing, not them, you have every motivation to get it right.

Raph wrote:"The rest of the rim remains at the same distance from the hub as when the wheel isn't loaded, and the spokes at the same tension."

So effectively the rim must be "rubbery" enough to accommodate the slackening of spokes, i.e. the circumference gets shorter? That's the only way that one bit can get closer to the hub without any other bit getting further from the hub - unless the rim pretzels of course... ok... I'd assumed that it was less likely to compress than (even several) steel spokes were to stretch.

Don't forget there are bits of rim in between the spokes, with nothing to stop them getting a little further from the hub. It's these bits either side of the bottom spoke that take up the extra circumference.

If you've got a front wheel built to a tension of 50kgf, positioned so there's a spoke at the bottom, and put a 30kg load on it, then the bottom spoke has its tension reduced to maybe 18.1kgf, and the two spokes either side have theirs increased to maybe 51kgf. All the other spokes remain at a tension of 50kgf.

If you have a stiffer rim (eg deep section aero), there is a longer section that is affected by the deformation caused by the weight the wheel is supported. If you had a 36 spoke aero rim, there would be several of the bottom spokes that saw a reduced tension. However in practice you just have fewer spokes that are further apart, so it's still only the bottom spoke or two that are affected.

hubgearfreak wrote:

andrew_s wrote:Sapim quote a strength of about 1400N/mm2, a double butted spoke is about 2.5mm2 in cross section, so that would give an expected breaking load of about 350kg.

is that from a testing machine that holds the spoke as it would be held in a wheel? its a reassuringly high figure

No, it's the strength of the wire the spoke is made from.
It doesn't allow for any weakening at the head bend, at the threads, or that the nipple, rim or hub may not be as strong as the spoke.

Raph wrote:"(in theory) you can build a wheel with no twist by backing off with the spoke key slightly after tightening (and vice-versa when loosening a spoke)."

I do that as a matter of habit, but I don't trust it enough to leave the wheel as it is at the end - especially since as you mention different spokes obviously twist different amounts. I did once try to measure how much a spoke twisted so I'd know how much to back off, but I gave up on that pretty quick!

You need to back off a surprisingly large amount - something like tighten a full turn, then back off 3/4 turn, to tighten a spoke by 1/4 turn.
The way to see it is to build with bladed spokes like Sapim CX-ray, not that it's a cheap option.

Raph wrote:What else would there be?

http://www.sjscycles.co.uk/category-Too ... ld-826.htm to name a few!

I started off with using just my frame, then bought a secondhand wheel jig.

Sorry, my imagination (and curiosity) was running wild - I thought you were implying you now use tension gauges and other fancy things I might not have heard of!

I still use the absolutely terrible cheapo wheel jig I bought about twenty years ago. Really all you need is a spoke key - everything else just makes the job more pleasant, that's all. The dishing tool's useful - before I got that I used to hold a pencil against the spokes right by the hub and line up the end of it with the nearest and furthest edges of the rim by sight (at any one time two of the three things would be wildly out of focus!), then put my thumb on the pencil to mark the spot where it met the flange - then I'd turn the wheel over and check the other side. Wheels I built at home years ago and centred the rim by that method have turned out to be bang-on when checked with the dishing tool - but squinting at an out-of-focus rim is pretty tedious.


"You need to back off a surprisingly large amount - something like tighten a full turn, then back off 3/4 turn, to tighten a spoke by 1/4 turn."

Sounds extreme but I can believe it. I usually lube the ferrules before lacing up by putting a blob of grease on the blunt end of a pencil and dabbing it on the ferrules where the nipples sit in them - only difference it makes is I can feel more of the springyness in the spoke as it twists rather than battling against the friction of a dry contact between nipple and ferrule, so I have some slight hope of backing it off the right amount by feel - fairly ineffective really but I keep doing it out of vain hope!


Does anyone remember chromed spokes? The chrome was never as flexible as the rest of the spoke - the two always parted company eventually.

And why in heaven's name was "rustless" ever called "rustless", since it did something so similar to rusting as to be effectively the same, albeit went dirty grey rather than reddish brown?


Well - great discussion - I've done nearly no work today, but it's given me lots to ponder on those less interesting rides! Still grappling with the notion that slackness breaks spokes when it's the ones in the tightest group - i.e. drive side rear - that break the most...

The drive side spokes [1] break more often because they're going through the greatest stress cycle, as I understand it. The left-hand spokes, having a more favourable bracing angle, don't change their tension as much when ridden. I must dig out "The Bicycle Wheel" and check it. A 36-spoke derailleur wheel is virtually an 18-spoke wheel, with the heavy dish required.


[1] just to mess with your mind, the left-hand spokes are the drive side on a Sturmey-Archer 3-speed hub, but only in low gear - the right-hand spokes are the drive side in normal and high gear. Of course, SA wheels are dishless, or nearly so.

"they're going through the greatest stress cycle"

Do you mean the greatest span of stress from least to most? And do you then reckon in a looser wheel that would be a greater span still?


"A 36-spoke derailleur wheel is virtually an 18-spoke wheel, with the heavy dish required."

Yes - and the angle of the non-drive side is such that I often think of it as spokes that do not very much more than keep the rim in lateral position. When truing it's almost, but not quite - as straightforward as drive side for up-down adjustment, non-drive side for sideways adjustment.


The last Sturmey I took apart was literally decades ago - I can't remember how it worked other than the principle of planet gears - from what you say it sounds as though the two flanges are separate - or at least can move independently of each other. I've rebuilt a few (years ago now) and remember the barrel being one piece, so both flanges would pull equally. I'm curious now - I'll have to go and take one apart!

rogerzilla wrote:just to mess with your mind, the left-hand spokes are the drive side on a Sturmey-Archer 3-speed hub, but only in low gear - the right-hand spokes are the drive side in normal and high gear. Of course, SA wheels are dishless, or nearly so.

interesting, but i'm with raph on this one...

Raph wrote:remember the barrel being one piece, so both flanges would pull equally. I'm curious now - I'll have to go and take one apart!

the outer case (tincan) is so substantial a piece of steel i can't see one spoke flange moving in relation to the other even by the tiniest amount

Yes, on a large-diameter Sturmey barrel there is practically no wind-up under torque. However, on a small-barrelled derailleur hub it is apparently possible to wreck one (so the "Campagnolo" script is visibly distorted by the twist!) if you lace it radially on the right-hand side.

Velocio wrote:I bought a new Dawes Horizon in March last year ...in September one of the spokes on my front wheel suddenly snapped with a loud 'ping' while cycling on a flat road with no ulterior cause.

I went to my dealer where I purchased it expecting them to replace the spoke as it was ...I thought ...under it's first year's guarantee. The dealer charged me £10 for labour and relacement costs ...saying that after nearly six month's cycling this was to be expected.

I'd previously had a Dawes cycle for 5 years which I'd cycled 15,000 miles and not one spoke had snapped. In fact ...since starting cycling aged 10 ...I'm now in my fifties ...and after some 100,000 miles cycling ...on various cycles ...not once has a spoke snapped

I contacted Dawes who said it wasn't their responsibility ...it was all down to the judgement of the dealer

This week another spoke snapped. I think the cycles of today are made of inferior materials. I'm not happy with Dawes, and I won't be going back to my dealer this time ...or ever again! :(

I have in regular use a 32 hole front wheel (27") double butted spokes I built about 40 years ago. Spokes should not break particularly todays and in a front wheel. I had problems with a tandem rearwheel during a New Forest cycling week about 30 years ago. At that time there was a regular advert in the magazine for brass washers to fit under the heads of spokes (quite small) I rebuilt using these washers and no trouble since, however with regard to your problem, as others have said any new bike breaking spokes after 6 months is unfit for purpose and should be delt with by the retailer.

I love my Brompton but braking spokes on the sprocket side of the hub are the vain of my riding and stop me touring the world on it..Is it an easy fix if you know how?

JC4LAB wrote:I love my Brompton but braking spokes on the sprocket side of the hub are the vain of my riding and stop me touring the world on it..Is it an easy fix if you know how?

I'd take the wheel apart - check the straightness of the rim on a flat surface - if it's wonky then give up on it and get a new one because evenness of spoke tensions will have to be compromised to get it straight. It's most likely you'll need a new rim - rims usually "settle" over time and tend to come out wonky when dismantled even if the wheel was a good one. If you've been replacing spokes rather than rebuilding the wheel from scratch then the rim will very likely be duff by now.

In short, rebuild it with a new rim and do it as well as you can - spend a whole day on it if necessary. If you're not into wheelbuilding get someone good to do it, preferably someone near enough to you so they know if it's a duff build you'll be back to visit them, and not someone with the attitude of the lbs that sold the OP his Dawes!