Wheel-building question: tensions on 26"=700c?

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sarniacycle
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Joined: 17 Jun 2012, 1:19pm

Wheel-building question: tensions on 26"=700c?

Post by sarniacycle »

Good morning

For the same type/diameter of spoke, built in same pattern in a rim with the same number of holes, tension should be the same whether in a 26" wheel or a 700c, one? i.e. spoke length does not affect tension if everything else is equal...or does it...?

Practical reason for this - I want to know if I can reproduce the tensions from a known "good" 26"/559 wheelset over to a new, 700c one I'm building (where all other parameters are the same).

Also curious to know what tips people have to know the tension they've reached is right (besides tensionmeters). Experience, right?!

Many thanks.
Jamesh
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Joined: 2 Jan 2017, 5:56pm

Re: Wheel-building question: tensions on 26"=700c?

Post by Jamesh »

I would have thought so but I'm no expert having only built two pairs of wheels

Others might say otherwise.

I use the patented "ping o meter" technology

NDS have a dull ping, DS have a sharp ping and front in between all very scientific!

I do worry doing 40mph down a hairpin bended decent!!

Cheers James
rogerzilla
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Re: Wheel-building question: tensions on 26"=700c?

Post by rogerzilla »

The only real upper limit* on tension is the rim either pringling (unlikely with modern rims) or cracking/pull-through at the spoke holes (equally likely with 26" or 700c), so I would use the same tension as for 26".

Bear in mind that the ping of a 700c spoke at the same tension and spoke pattern will be a bit lower, because it's a bit longer.

I have a tensionometer as a final check but I actually build by feel: when well-lubed nipples feel hard to turn, that's enough. "Hard" comes from experience!

*hub flanges can be ripped off, but only from bad hubs that deserved to die
iandusud
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Re: Wheel-building question: tensions on 26"=700c?

Post by iandusud »

I appreciate that you are trying to reproduce the spoke tension of a known good wheel. However ideal spoke tension is a bit subjective and TBH not an exact science. What I'm saying is that your known "good wheel" isn't necessarily perfectly tensioned. The ideal spoke tension will depend on a number of factors but there is a fair bit of leeway between too loose and too tight. So I would say don't get too obsessive about it. Don't wind up the spoke nipples like there was no tomorrow at one end of the scale. At the other end try squeezing adjacent spokes and they shouldn't feel too springy. This is all assuming a wheel with a reasonable spoke count, i.e. 32 or more. On wheels with less spokes the tension is more critical but even then common sense should see you through. I've been building wheels for 40 years, many of those on a professional basis, and I've never used a spoke tension meter.
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531colin
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Re: Wheel-building question: tensions on 26"=700c?

Post by 531colin »

sarniacycle wrote: 8 Apr 2021, 12:36pm Good morning

For the same type/diameter of spoke, built in same pattern in a rim with the same number of holes, tension should be the same whether in a 26" wheel or a 700c, one? i.e. spoke length does not affect tension if everything else is equal...or does it...?

Practical reason for this - I want to know if I can reproduce the tensions from a known "good" 26"/559 wheelset over to a new, 700c one I'm building (where all other parameters are the same).

Also curious to know what tips people have to know the tension they've reached is right (besides tensionmeters). Experience, right?!

Many thanks.
The limit of spoke tension is set by the rim.
With a strong rider and a narrow, light (ie flexible) 700c rim on a highly-dished wheel you can get into the situation where if you tighten the NDS spokes enough so that they don't loosen in service, then the DS spokes are tight enough to crack the rim at the spoke holes in use. The only solution to this is to threadlock the NDS nipples and go steady with the tension so you don't over tension the DS. There is no substitute for a tension gauge for wheels like this.
If you are using a big strong rim in a wheel with a sensible amount of dish, then life is a lot easier; there is a whole world of difference between building (say) a 26" sputnik wheel on an 8 speed 135mm hub and a 700c lightweight rim on an 11speed 130mm hub.
With a 26" Sputnik you can almost put all the bits in a box, shake it up, and tip out a built wheel; the other one can take most of an afternoon.
The single most important thing in building wheels is stress-relief; second most important is balancing the tension. Building for yourself, you can decide on how much to compromise evenness of tension in pursuit of perfect roundness or trueness; customers tend to expect perfectly round and true wheels, and they don't realise that getting them like that means non-uniform tension and reduced durability.
mig
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Re: Wheel-building question: tensions on 26"=700c?

Post by mig »

531colin wrote: 8 Apr 2021, 3:41pm
sarniacycle wrote: 8 Apr 2021, 12:36pm Good morning

For the same type/diameter of spoke, built in same pattern in a rim with the same number of holes, tension should be the same whether in a 26" wheel or a 700c, one? i.e. spoke length does not affect tension if everything else is equal...or does it...?

Practical reason for this - I want to know if I can reproduce the tensions from a known "good" 26"/559 wheelset over to a new, 700c one I'm building (where all other parameters are the same).

Also curious to know what tips people have to know the tension they've reached is right (besides tensionmeters). Experience, right?!

Many thanks.

With a 26" Sputnik you can almost put all the bits in a box, shake it up, and tip out a built wheel;
definitely going to try this! :wink:
Tiberius
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Location: North East England

Re: Wheel-building question: tensions on 26"=700c?

Post by Tiberius »

531colin wrote: 8 Apr 2021, 3:41pm customers tend to expect perfectly round and true wheels, and they don't realise that getting them like that means non-uniform tension and reduced durability.
That's a really interesting point. I've definitely learnt something there. Thank you.
sarniacycle
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Joined: 17 Jun 2012, 1:19pm

Re: Wheel-building question: tensions on 26"=700c?

Post by sarniacycle »

Jamesh wrote: 8 Apr 2021, 12:59pm
I use the patented "ping o meter" technology

NDS have a dull ping, DS have a sharp ping and front in between all very scientific!
Thanks James, just hope my ping o meter is as reliable and accurate as yours!
sarniacycle
Posts: 199
Joined: 17 Jun 2012, 1:19pm

Re: Wheel-building question: tensions on 26"=700c?

Post by sarniacycle »

531colin wrote: 8 Apr 2021, 3:41pm
sarniacycle wrote: 8 Apr 2021, 12:36pm Good morning

For the same type/diameter of spoke, built in same pattern in a rim with the same number of holes, tension should be the same whether in a 26" wheel or a 700c, one? i.e. spoke length does not affect tension if everything else is equal...or does it...?

Practical reason for this - I want to know if I can reproduce the tensions from a known "good" 26"/559 wheelset over to a new, 700c one I'm building (where all other parameters are the same).

Also curious to know what tips people have to know the tension they've reached is right (besides tensionmeters). Experience, right?!

Many thanks.
The limit of spoke tension is set by the rim.
With a strong rider and a narrow, light (ie flexible) 700c rim on a highly-dished wheel you can get into the situation where if you tighten the NDS spokes enough so that they don't loosen in service, then the DS spokes are tight enough to crack the rim at the spoke holes in use. The only solution to this is to threadlock the NDS nipples and go steady with the tension so you don't over tension the DS. There is no substitute for a tension gauge for wheels like this.
If you are using a big strong rim in a wheel with a sensible amount of dish, then life is a lot easier; there is a whole world of difference between building (say) a 26" sputnik wheel on an 8 speed 135mm hub and a 700c lightweight rim on an 11speed 130mm hub.
With a 26" Sputnik you can almost put all the bits in a box, shake it up, and tip out a built wheel; the other one can take most of an afternoon.
The single most important thing in building wheels is stress-relief; second most important is balancing the tension. Building for yourself, you can decide on how much to compromise evenness of tension in pursuit of perfect roundness or trueness; customers tend to expect perfectly round and true wheels, and they don't realise that getting them like that means non-uniform tension and reduced durability.
Thanks Colin, these points are very helpful practically and to understand a bit more of the reasoning behind why experienced wheel buildings do certain things in a certain way. Cheers!
sarniacycle
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Joined: 17 Jun 2012, 1:19pm

Re: Wheel-building question: tensions on 26"=700c?

Post by sarniacycle »

Thanks to everyone above, this is all very reassuring and just what I needed!
Bonefishblues
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Re: Wheel-building question: tensions on 26"=700c?

Post by Bonefishblues »

rogerzilla wrote: 8 Apr 2021, 1:21pm The only real upper limit* on tension is the rim either pringling (unlikely with modern rims) or cracking/pull-through at the spoke holes (equally likely with 26" or 700c), so I would use the same tension as for 26".

Bear in mind that the ping of a 700c spoke at the same tension and spoke pattern will be a bit lower, because it's a bit longer.

I have a tensionometer as a final check but I actually build by feel: when well-lubed nipples feel hard to turn, that's enough. "Hard" comes from experience!

*hub flanges can be ripped off, but only from bad hubs that deserved to die
Just for comedy value, I did that to a rim as a young man, and took it to the LBS to see if they could salvage it. when they eventually stopped laughing I figured that was a no, then :lol:
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geomannie
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Re: Wheel-building question: tensions on 26"=700c?

Post by geomannie »

Jamesh wrote: 8 Apr 2021, 12:59pm I would have thought so but I'm no expert having only built two pairs of wheels

Others might say otherwise.

I use the patented "ping o meter" technology

NDS have a dull ping, DS have a sharp ping and front in between all very scientific!

I do worry doing 40mph down a hairpin bended decent!!

Cheers James
I too have built maybe half a dozen wheels using the "ping o meter" TM. You are not the only who worries at 40mph! :D
geomannie
rogerzilla
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Re: Wheel-building question: tensions on 26"=700c?

Post by rogerzilla »

A pringle is generally elastic and will vanish if you slacken each spoke about half a turn. It is basically Euler buckling in a ring rather than a column - the rim is trying to get out of the way of the compressive load. The narrower and lighter the rim, and the smaller the box section, the more likely it is to pringle.

To get a permanent pringle, you really have to be going for it!
Bonefishblues
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Location: Near Bicester Oxon

Re: Wheel-building question: tensions on 26"=700c?

Post by Bonefishblues »

rogerzilla wrote: 8 Apr 2021, 9:00pm A pringle is generally elastic and will vanish if you slacken each spoke about half a turn. It is basically Euler buckling in a ring rather than a column - the rim is trying to get out of the way of the compressive load. The narrower and lighter the rim, and the smaller the box section, the more likely it is to pringle.

To get a permanent pringle, you really have to be going for it!
I omitted to learn about the spoke-slackening bit with rather disastrous consequences :lol:

Me truing a wheel:
https://youtu.be/Z4fBbhyzE9A
PH
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Re: Wheel-building question: tensions on 26"=700c?

Post by PH »

If your ear isn't as finely tuned to distinguishing pings as well as some seem to be - There's an app for it, well there's probably a choice of them, but I use this one, which seems more consistent than the Park tension meter I have access to
https://www.youtube.com/watch?v=ChFIIe0aPb4
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