Broke a spoke; Bike is 30 years old... best to get wheel rebuilt?

[T4tomo]

Isn't a general rule of thumb if one spoke breaks, replace it and trust it was a one off, if another goes its more indicative of an issue so rebuild the wheel.

If you are then going to the labour time or expense to rebuild a wheel then its sensible to do that with a new rim to maximise the time until next rebuild, given a rim is the cheapest part of the rebuild expense.

 

[PedallingNowhereSlowly]

As another 'trailer tower', just curious what you've got (diy / commercial ?) and what sort of loads you typically carry?

A Carry Freedom 'Y' (large) which I have, judging by the state of it, used quite a lot historically but for most of the last ten years it's sat in the garage. Over the last 6 months I've been getting my fitness back and now it's used mainly when I'm doing DIY jobs, DIY jobs for other people, gardening so it's skip runs, tools and other random odds and sods. I'd maybe use it for some bike packing in the summer if time allows.

 

[PedallingNowhereSlowly]

So I've been doing some digging around the intertubes. I might just get a new wheel built courtesy of Spa Cycles. It's not that expensive. And it turns out that the 7 speed hyperglide cassette should work just fine on a 10 speed hub with a spacer, at the expense of a little more off set.

The only other issue is that I'd need to swap the quick release for a solid axle* - with 4mm thread to spare for mounting the trailer hitch. Only issue with that is the axle I've got has a 9mm diameter and a new hub typically will need a 10mm axle, so I'll have to source a suitable replacement.

*I'm a bit uneasy about quick release skewers when they are used with a trailer hitch

 

[albion]

Fatigue here seems to be the term used for wear due to friction and or movement.
If the wheels looked true and spokes felt fully tensioned then it is still most likely that that spoke was the loosest.

The two either side are thus most at risk, but less so than any normal loose spoked wheel.

 

[Ajax Bay]

Fatigue here seems to be the term used for wear due to friction and or movement.
If the wheels looked true and spokes felt fully tensioned then it is still most likely that that spoke was the loosest.

The two either side are thus most at risk, but less so than any normal loose spoked wheel.

Sorry you don't understand: who is using the term "fatigue" thus?
The failure is not due to either friction or movement.
Anyway why would the "loosest" spoke fail before a properly tensioned spoke? What is the mechanism?
Fatigue (in the spoke context) is caused by millions of repeated variations of tension (bending or torsional cycles in other contexts).
Each spoke cycles through low(er) tension and high tension (on the right side rear wheel maybe between 1550N and 1000N (say)) every rotation. The strain caused by that stress are well within elastic limits. Take a reasonable year's riding of 10,000km. That's close on 5 million cycles; annually. If rim braked and well built the rim will 'always' go first. Maybe we'll see more spokes eventually fail through fatigue with disc brakes.
Decent stainless steel spokes (Sapim/DT Swiss) will have a very high fatigue limit.

 

[albion]

You seem to be saying bending is not friction.
The bending of course varies according to both spoke tension and weight.
Wel all know bending metal causes heat. Via friction.

 

[Ajax Bay]

"Bending" is not "friction".
Spokes do not "bend", once installed and tensioned.
I referenced (repeated) (elastic) bending because it can result in failure through fatigue. Not relevant to spokes.
Windy in this bit of the Earth today but it is not flat.

 

[albion]

You cannot remove bending/friction from the fatigue equation, even if it is all at a microscopic level.
There is even 'static friction', yet it is still friction. Heat from bending is indeed microscopic friction.

That heat will be what causes spokes to further harden eventually localising fatigue cracks where the elastic metal becomes unelastic metal.
Those cracks will be more locallised at points where the spoke meets the rim. It is there you have your mix of static and none static friction.

 

[Ajax Bay]

You are making it up and suspect you might be an AI bot.
The spokes are not bending they are stretching and contracting, 500 times a km.
There is no relative movement at the rim and there is no movement at the hub (flange). The spoke remains in tension (at least 500N - maybe half your bodyweight, if you're a big lad). No movement = zero friction.
A j spoke's weakest point is the right angle bend and where most spokes fail through fatigue.
Another typical failure point is at the first thread which can be a stress riser. Parting there is more likely if the spokes used are too short and one of those rolled threads is exposed (as opposed to protected by the nipple).

 

[albion]

Rofl.

Everything I put there is from the science fact. There seems to be a spanner in the spoke works.

 

[Ian H]

Rofl.

Everything I put there is from the science fact. There seems to be a spanner in the spoke works.

Any links to this 'science fact'?

 

[Big John]

Did all this start out as a bust spoke? God help anyone who has a real problem.

 

[albion]

Well, it started 'you bust a spoke, so they will all bust'.

Science and art merge.

 

[Yellow Saddle]

You cannot remove bending/friction from the fatigue equation, even if it is all at a microscopic level.
There is even 'static friction', yet it is still friction. Heat from bending is indeed microscopic friction.

That heat will be what causes spokes to further harden eventually localising fatigue cracks where the elastic metal becomes unelastic metal.
Those cracks will be more locallised at points where the spoke meets the rim. It is there you have your mix of static and none static friction.

I want to amend my easlier statement of you not understanding tensioned structures. I was wrong. It shoud read: " You don't understand tensioned structures, friction, metallurgy, physics, bicycles or structured debate." *

* Note that this statement is not necessarilly complete. I reserve the right to add to it.

 

[Ian H]

Personally, I'd replace one spoke and cross fingers. If another goes... well, I might replace that too, but I'd be thinking about a rebuild.