32 or 36 spokes

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irc
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32 or 36 spokes

Postby irc » 13 Oct 2018, 3:10pm

On a discussion about touring wheels elsewhere some posted the theory that

As it is a multiple of 16, 32 spokes may actually be stronger/more durable than 36


I've asked for the theory behind this as I have always thought that all else equal a 36 spoke wheel (700c) would be stronger than a 32 spoke wheel.
But pending any reply on that forum has anyone here ever heard this idea?

Surely if 32 spoke wheels were stronger there would be no market for 36 spoke wheels?.

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RickH
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Re: 32 or 36 spokes

Postby RickH » 13 Oct 2018, 3:17pm

I can't think of any reason why a multiple of 16 spokes should be special. Unless the spoking is asymmetrical (like Campag/Fulcrum), with a different number on each side of the rear wheel, they only have to be in multiples of 4.

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Chris Jeggo
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Re: 32 or 36 spokes

Postby Chris Jeggo » 13 Oct 2018, 3:34pm

+1
As it is a multiple of 16, 32 spokes may actually be stronger/more durable than 36

... sounds more like numerology than physics or engineering to me.

When I was a lad we had 32 front and 40 rear, a pattern of 4 repeated as often as required/desired, recognising that the loads on the front and rear wheels are different. Then the industry decided 36/36 would be cheaper.

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RickH
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Re: 32 or 36 spokes

Postby RickH » 13 Oct 2018, 4:03pm

Chris Jeggo wrote:+1
As it is a multiple of 16, 32 spokes may actually be stronger/more durable than 36

... sounds more like numerology than physics or engineering to me.

When I was a lad we had 32 front and 40 rear, a pattern of 4 repeated as often as required/desired, recognising that the loads on the front and rear wheels are different. Then the industry decided 36/36 would be cheaper.

I thought that 36/36 was the continental pattern & 32/40 the British one & probably came about, at least in part, due to the difference in loading with British tourers tending to use saddlebags on the rear with continental (particularly French) riders using more front loading for luggage.

Did the transition come about around the same time as 700c became the "universal" wheel size for road bikes?

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Re: 32 or 36 spokes

Postby Brucey » 13 Oct 2018, 4:18pm

RickH wrote: ...Did the transition come about around the same time as 700c became the "universal" wheel size for road bikes?


Not really; for about ten years mass produced sports bikes used 36/36 wheels built with 27" rims and tyres.

FWIW I know of no particular reason why a multiple of 16 spokes should build into a better wheel than a multiple of 4; more spokes is always better of course, for wheel strength at any rate.

cheers
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foxyrider
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Re: 32 or 36 spokes

Postby foxyrider » 13 Oct 2018, 4:52pm

Surely that's the total for a pair :lol: my bullet proof Zonda's are 16/21 so half fulfill the x4 thing (although the front is actually radially spoked)
Convention? what's that then?

Airnimal Chameleon touring, Orbit Pro hack, Orbit Photon audax, Focus Mares AX tour, Peugeot Carbon sportive, Owen Blower vintage race - all running Tulio's finest!

reohn2
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Re: 32 or 36 spokes

Postby reohn2 » 13 Oct 2018, 6:09pm

More spokes,less stress per spoke,so 36 more durable than 32 all else being equal.
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Greystoke
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Re: 32 or 36 spokes

Postby Greystoke » 13 Oct 2018, 6:26pm

26" wheels with 36 spokes are even stronger :D

belgiangoth
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Re: 32 or 36 spokes

Postby belgiangoth » 13 Oct 2018, 11:24pm

I've heard the 32 is stronger than 36 thing before. No credible reason given though.
There isn't much weight advantage to saving a couple spokes, but the reverse argument - that *MIGHTY SPRINTERS* manage not to break low spoke wheels - suggests to me that there's no point worrying about it either way.
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yostumpy
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Re: 32 or 36 spokes

Postby yostumpy » 13 Oct 2018, 11:38pm

I reason that 36 is stronger, urely by common sense, so run 36 rear 32 front.

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Re: 32 or 36 spokes

Postby reohn2 » 13 Oct 2018, 11:50pm

Two things:-
1)Having the same spoke count front and rear means when touring if you trash a rear rim(which is the wheel most likely),the front rim can be laced into the rear and any cheap front (less stressed)wheel can be used to continue.
2)A 36spoke wheel is easily trued up than a 32 roadside in the event of a spoke breakage(which will almost certainly be the driveside rear).
And should a spoke break in a 20 spoke wheel yer goosed good and proper,won't be riding anymore that day and may have a long walk ahead of you :shock:
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Brucey
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Re: 32 or 36 spokes

Postby Brucey » 14 Oct 2018, 1:55am

belgiangoth wrote:
There isn't much weight advantage to saving a couple spokes, but the reverse argument - that *MIGHTY SPRINTERS* manage not to break low spoke wheels - suggests to me that there's no point worrying about it either way.


spokes fail by fatigue; 'the mighty sprinters' won't break the shiny new wheels they are riding that day in the TdF by fatigue. Spokes do break in race bike wheels though; in last year's TdF I think it was a broken spoke that may have contributed to a situation where CF was attacked.

Regarding the whole 'my wheels without many spokes in haven't broken yet, therefore they must all be alright' line of comment: This is a false argument in that something parts can be unacceptably reliable yet nine out of ten users might see no problems in their use. If the part is safety critical even one failure in a hundred is a complete disaster and one every many thousands can be enough to (say) trigger a recall in products like cars.

Wheels work differently depending on how stiff the wheel rim is. The stiffer the rim is, the lower the radial fatigue loading on the spokes is, in an evenly tensioned wheel. However when the wheel is laterally loaded, the fatigue loads on such wheels are still pretty high. So in some uses the expected fatigue life of spokes in low spoke count rims ought to be OK. It very often isn't though for all the usual reasons; bad fit of spokes, bad spokes, bad stress relief, uneven tension in spokes... you name it.

When a spoke does break in such wheels the wheel is liable to go out of true more than a wheel with a greater number of spokes. Worse yet, if you do manage to ride on such a wheel with a broken spoke, the rim often 'takes a set' such that the wheel will never be any good again, i.e. the rim is now bent and the wheel won't be straight and evenly tensioned, not at the some time anyway.

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ANTONISH
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Re: 32 or 36 spokes

Postby ANTONISH » 14 Oct 2018, 9:30am

Brucey wrote:
When a spoke does break in such wheels the wheel is liable to go out of true more than a wheel with a greater number of spokes. Worse yet, if you do manage to ride on such a wheel with a broken spoke, the rim often 'takes a set' such that the wheel will never be any good again, i.e. the rim is now bent and the wheel won't be straight and evenly tensioned, not at the some time anyway.

cheers


I had this problem with a pair of Shimano 105 16/20. They were nice wheels to ride until I broke a spoke - thereafter they became unreliable - and I'm quite small.
Incidentally while on an audax I came across a group one of whom poor soul had broken a rear spoke on a wheel that had very few spokes - I would estimate 16 - tightening adjacent spokes to compensate wasn't a practical proposition. All I could offer was the train times at the nearest station.

I often carry a kevlar string emergency spoke but unfortunately hadn't got it with me on that occasion - if I were to use low spoke count wheels that is something I wouldn't be without.
I only use 32's or 36's now.

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Re: 32 or 36 spokes

Postby Brucey » 14 Oct 2018, 9:43am

FWIW I think the idea that a fourfold symmetry in the spoking pattern (which does require a multiple of 16 spokes I think) might be stronger arises from the way in which wheels fold up under lateral overload; the 'taco' deformation pattern requires that the rim undergoes a deformation that is arguably best resisted by a four-fold spoking pattern.

In practice this effect is likely to be completely overwhelmed by simply having more spokes in the wheel.

In answer to the question 32 or 36? I would sometimes say 'both'. Very often (with derailleur gears and modest loads) the rear wheel is best with 36 spokes and the front is best with 32. R2 makes a good point about being able to swap your chosen front rim into the rear wheel in an emergency so for a touring bike it probably makes most sense to use 36 front and rear, even if the front wheel doesn't really need more than 32 spokes.

cheers
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reohn2
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Re: 32 or 36 spokes

Postby reohn2 » 14 Oct 2018, 9:50am

Greystoke wrote:26" wheels with 36 spokes are even stronger :D

And 32 spoke 26inch wheels are as strong as 700c 36spoke wheels :)
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