Spoke and nipple pulled through rim

[DaveReading]

A new failure mode for me after 60-odd years on two wheels.

Having noticed a mm or so of runout on the back wheel a couple of weeks ago, and made a mental note to get the spoke key out, that was overtaken by events today when a spoke started flapping around and to my horror I realised that the nipple was still attached and had pulled through the rim.

How common is that? I know spokes are always in tension, but I hadn't expected such a vivid demonstration.

Obviously a new wheel is called for. I'm half tempted to also order a new rim and try my hand at wheel-building.

 

[Smokin Joe]

Not an Aksium, is it? I had one go on a wheel that was little more than a year old.

 

[DaveReading]

Not an Aksium, is it? I had one go on a wheel that was little more than a year old.

The wheel is the original fitted to my EBC tourer (bought in 2012).

No identifying marks, the spec describes it simply as "Revolution [EBC's brand name], Alloy, Double Wall, 32h"

If anyone can point me at a suitable, not-too-pricey, replacement I'd be very grateful (700C, 8-speed cassette, preferably Schrader valve rim, to take a 32c M+).

 

[Yellow Saddle]

That rim failed from a combination of metal fatigue and corrosion.

It is pretty common.

A spoke pulls on the rim with considerable force and pulls a "teat" from the rim. With every revolution, as a particular spoke hits the bottom at the road, the teat relaxes, because at that point the wheel is compressed.

With each revolution, you get a cycle of pull and relax. That alone fatigues the aluminium over time (not really time, but cycles).

Further, the rim is hard anodised, that's the black coating you see.

Anodising is nothing other than a hard, very hard layer of aluminium oxide that sits one half on top, and one half inside the rim. Like a heavily scabbed knee, when you bend a hard coating it cracks. That crack propagates into the soft, vulnerable material underneath. If you flinch at this point, you understand exactly what happens in an anodised rim.

With time, that crack spreads, corrosion opens it up further because alu oxide corrosion crystals are many times bigger than plain alu molecules.

The crack spreads, works right through and bang, your spoke has nothing to pull on.

It is new rim time. However, you have to get EXACTLY the same rim otherwise the spokes will be the wrong length.

Good luck.

 

[DaveReading]

Thank you for the comprehensive explanation.

I appreciate that spoke tension is continually varying with rotation of the wheel (hence the potential for fatigue), but I'd been under the impression that a spoke was nevertheless always under some tension, rather than under compression at some points in the rotation ?

 

[fossyant]

Saying nothing, but there is a huge amount of corrosion there. Did you 'ever' wash the bike.

Abused, so it will fail... you need to clean the bike. I have rims loads older than that.

 

[fossyant]

The rim is a mess... simple. Poor cleaning/maintenance - there is a huge amount of deterioration, which only occurs with complete neglect.

Bikes need a clean once in a while, well more actually.

 

[Ian H]

For many years I have only used double-eyeletted rims, and avoided the hard anodising on the grounds that it can get a bit messy when the surface wears through. I build my wheels pretty tightly, but have never had a spoke pull through.

I did once (many years ago) wear through a Mavic rim, so that the hook-bead was detached in one place. I recall being very surprised at how elastic and hard to bend-and-break the alloy was.

 

[DaveReading]

I'll consider myself suitably chastened.

 

[Ajax Bay]

With every revolution, as a particular spoke hits the bottom at the road, the teat relaxes, because at that point the wheel is compressed.
With each revolution, you get a cycle of pull and relax. That alone fatigues the aluminium over time (not really time, but cycles).

I appreciate that spoke tension is continually varying with rotation of the wheel (hence the potential for fatigue), but I'd been under the impression that a spoke was nevertheless always under some tension, rather than under compression at some points in the rotation ?

Dave - you are correct in thinking all spokes stay in tension all the time and they are never under compression at any point of the wheel's revolution. "[As] a particular spoke hits the bottom at the road" that vertical spoke is at its least tension so the part of the rim around the spoke hole, as @Yellow Saddle says, is more relaxed than at other positions (during the wheel's rotation), hence the "cycle of pull and relax" and eventual fatique.

 

[overmind]

I've been very happy with a Decathon rear wheel I bought several years ago.

https://www.decathlon.co.uk/triban-...MIqMrqkrWI4AIVyQrTCh1V-wsyEAQYASABEgJMiPD_BwE

 

[rogerzilla]

Road salt doesn't help. I've never had this happen to me although some black rims (e.g. DT, which I otherwise highly recommend) lose the anodising immediately around their eyelets, indicating something is going on. There's usually powdery corrosion too, and I suspect the s/s eyelet frets against the rim and keeps a fresh aluminium surface exposed for galvanic action.

 

[Ming the Merciless]

Dave - you are correct in thinking all spokes stay in tension all the time and they are never under compression at any point of the wheel's revolution. "[As] a particular spoke hits the bottom at the road" that vertical spoke is at its least tension so the part of the rim around the spoke hole, as @Yellow Saddle says, is more relaxed than at other positions (during the wheel's rotation), hence the "cycle of pull and relax" and eventual fatique.

Think of it as pull hard and pull not so hard, rather than relax.

 

[DaveReading]

Thanks for all the feedback.

I'm not too upset about a 7-year-old rim succumbing to the elements - my tourer gets rode hard and put away wet, as they say.

Though it's been a salutory experience trying to source a replacement with a similar, somewhat agricultural, spec: 700c, 36h, Schrader valve, rim brakes, 135m OLN, wide enough to take a 32c M+ (current rim outer width is 24 mm), freehub, Q/R. None of the usual retailers (online or local) seem to stock that combination as far as I can see, so it's off to eBay while trying to avoid Brand X rubbish and ads that omit crucial information like rim width or OLN size.

 

[Ajax Bay]

If you can find one satisfying your spec but for a Presta valve, enlarging the valve hole so a Schrader valve will fit is simple and risk free.