1. ## How do get such high tension in your spokes?

I am baffled by this. I keep buying too long spokes, I've been so frustrated that all the calculators seem to be off, or so I thought. As I'm building the wheel they are poking through the nipples up to 3 or 4 mm. But then I take one off to compare it to a fresh one from the box of 72 DT Competition (14/15) spokes and find that it is 4 mm longer than the fresh one. I thought maybe I had grabbed a different spoke from somewhere else by mistake.

But no, after some testing, I realize I have hit the yield limit for the spoke. I just tried tightening a spoke more to see if it would stretch or if the tension would increse. I turned the nipple >5 complete turns: no increase in tension. I removed the spoke and it was 4mm longer than a fresh one. Thus, I hit the yield limit of the spoke. Simple, period, end of story. But my tensiometer says I'm in the low 70's (although the idiot thing doesn't have any units printed on it; I'm assuming its kgf). I do some math and find that that is just about right: a 1.8mm radius section is 1/250th of a square inch, 304 stainless steel has a yield strength around 35,000 to 40,000 psi, which is 40,000/250 = 160 lb. per spoke. Which is 73 kgf. So that makes sense with my readings.

But I read all the time on here people going over 120 kgf, over 140 even. Someone mentioned 169.

WTF? I'm baffled. And it seems, from what I read on the internet, that spokes aren't the limiting factor in a high tension wheel, that the rim is.

If I do a google search, people are saying that spokes can take much more stress than we put on them, and nobody ever mentions the issue of their spokes stretching (plastically) and thus hitting a limit of spoke tension. But I clearly have hit the yield limit. I have always felt that I had been building kinda weak wheels 'cuz my spoke tension is only n the 70's, but others go well over 100. I never understood how they could get such high tension.

Even Jobst Brandt, who seems to be one of the top bicycle wheel gurus, said that spoke tension rarely gets to 50% of their yield strength in some post on his website. But I have hit it. Fairly easily, in fact.

I don't get it.

2. I have never seen a spoke stretch. How are you measuring them?

3. Originally Posted by J.B. Weld
I have never seen a spoke stretch. How are you measuring them?
Held next to each other with the ends butted perpendicularly up against a flat surface.

These 2 spokes were from a newly opened box of 72 DT spokes, both 286mm, but one was stretched while building a wheel.

4. Can't argue with that picture. I've built a lot of wheels with that particular spoke, and replaced a lot of broken ones and have never personally seen that happen.

5. What tensiometer are you using?
.

6. Spokes are not plain 304 - they are a work hardened stainless, with a yield strength of 180+ kpsi. (See the sapim web site for examples) Maybe you have a bad batch or something.

If your wheel is truly built with the spokes at the yield limit, then give the spokes a good stress relieve squeeze, and they should fail.

7. Well, that's something I haven't seen before with DT competitions, the nipples usually start to round out well before the spokes stretch. I've seen it before with DT revolutions when I had to make large tension adjustments to make a bent wheel ridable and really cranked on it with the spoke wrench, but it's something I've yet to encounter on a regular wheel build.

If I had to take a guess I'd suspect that the tensiometer is either miscalibrated or measuring on a scale other than kilograms.

8. Also, how much are your spokes getting twisted?

9. Originally Posted by beanbag
Spokes are not plain 304 - they are a work hardened stainless, with a yield strength of 180+ kpsi. (See the sapim web site for examples) Maybe you have a bad batch or something.

If your wheel is truly built with the spokes at the yield limit, then give the spokes a good stress relieve squeeze, and they should fail.
Well, failing is stretching at this point. And they have already failed. A weird thing about most stainless steels is that their yield strength is about a third of their ultimate tensile strength. These spokes are not a typical stainless steel alloy, but their yield strength is nowhere near 180 kpsi.

10. Thanks for all your replies. I have figured it out, and it is that my tensiometer is not in kgf. Looking for a photo of the wheelsmith tensiometer I noticed that they come with a calibration sheet, which I must've lost a long time ago, and this is why there were no units printed on the scale, I should have thought of that. I thought it was really clever that they had designed a tensiometer that didn't care what diameter the spokes were. But they didn't.

The interesting thing for those reading this is that the yield strength of spokes is not as high as people think. Tensile strength is often quoted, but yield strength is what really matters, and for stainless steels it can be quite low compared to the tensile strength. It seems to be about 150 kgf for 14/15 butted DT spokes. I don't know exactly because I don't have the calibration sheet for my meter, but looking at other calibration sheets on the internet, the yield strength should be somewhere around 150 kgf, which is 85,000 psi, if not a little less. If you ever find yourself turning the nipple and the tension just isn't changing, you have hit the yield limit, and it's not that far away.

Wheelbuilding seems so much easier to me tonight than it did this morning.
I'm amazed that this issue hasn't come up much before, but I realize it's because of a few things coming together that made me get there. It started because I misinterpreted my tensiometer by a factor of about double/half. I got kinda insecure about my wheel building ability because I could never get my spoke tension as high as other people were getting. I would crank on those nipples, and they would round out, and people were seeming to get such high tensions even with aluminum nipple, and some people would just use dry spokes and nipples! This combined with a sort of guru notion of master wheel builders made me think I was just not getting it. And then the spokes were always too long, because they were stretching, but I thought there was some skill for choosing spoke lengths that I was missing. But it turns out I was just trying to get the tension much too high.

This resulted in me using grease on the threads so I could crank them up, and finally buying hex nipples so I could use a socket and a T-handle to torque them, so it was quite easy for me to torque them up. The final thing that let me do it, because apparently usually the rim will not withstand this much tension and it is the limiting factor, is that I am using a 50mm rim, a Surly Rabbit Hole, and I guess it's lateral stiffness let me get to such high tensions without it "Pringling".

I thought it was bizarre that this problem almost basically doesn't exist yet I was encountering it, I could find nothing about it on the internet, just people saying how strong these spokes really are, calculations that they can support 650 lbs each, but no mention of their yield strength and it's relative smallness compared to their ultimate tensile strength. But it makes sense now, with those few reasons coming together in a perfect storm, that this issue would occur very rarely.

Edit: spelling errors

11. Originally Posted by Godlikedog
Well, failing is stretching at this point. And they have already failed. A weird thing about most stainless steels is that their yield strength is about a third of their ultimate tensile strength.
That would only be true for annealed stainless, of which no self-respecting spoke is made. Upon work hardening, the ultimate tensile strength of stainless increase, but the yield strength increases even faster.
For example:
www.stal.com.cn/pdffile/302304304l305.pdf

and go to the chart on pg 6, "effect of cold work". For 302 stainless, which is what the sapim spokes are made of, the ultimate / tensile strength starts off as 90 / 40 kpsi annealed, and keeps increasing past 180 / 150 kpsi upon work hardening. This is consistent with the info on sapim's web page, and I can't comment on the DT swiss spokes because they won't say their secret recipe.

However, I see in Jobst Brandt's book a chart on spoke strength for DT swiss 1.8 swaged spokes that appears to have a yield point of 180 kg. But that is in the old days and spokes are supposed to be better now. If your spokes can't survive 150 kg, then that means that the DT Swiss Revolution spokes can't survive above 110 kg either.

BTW, you can easily calibrate your spoke meter by hanging a wire off a ceiling beam, and putting your weight onto it. Then use the tension meter on this wire.

12. tagged

13. Originally Posted by beanbag
For 302 stainless, which is what the sapim spokes are made of, the ultimate / tensile strength starts off as 90 / 40 kpsi annealed, and keeps increasing past 180 / 150 kpsi upon work hardening. This is consistent with the info on sapim's web page, and I can't comment on the DT swiss spokes because they won't say their secret recipe.

However, I see in Jobst Brandt's book a chart on spoke strength for DT swiss 1.8 swaged spokes that appears to have a yield point of 180 kg. But that is in the old days and spokes are supposed to be better now. If your spokes can't survive 150 kg, then that means that the DT Swiss Revolution spokes can't survive above 110 kg either.

BTW, you can easily calibrate your spoke meter by hanging a wire off a ceiling beam, and putting your weight onto it. Then use the tension meter on this wire.
I can't believe how little information there is on the web about this - the yield strength of spokes. I would expect a Google search to turn up data from people who have tested it and discussed it, comparing the different brands and analyzing it from every direction, but I just don't see it.

I hope someone else can do a little testing and see what they come up with.

Are people able to get over 110 kgf in their revolution spokes?

14. If you type in google "spoke strength testing", the first result that comes up is this one:

spoke strength--double butting - Road Bike, Cycling Forums ...

Apr 30, 2009 – I have tested the tensile strength of DT 14g and 14/15g spokes using a tensile testing machine. The results I got after pulling multiple spokes of ...

The guy says 715 lbs for 14/15 spokes. You can assume that is ultimate, so go to my chart, guess any alloy you want, and walk back the figure for yield strength.

But first you should calibrate your tension meter to see if anybody should care about spokes at the tensions you used.

15. This thread should serve as a reminder that you should do a cursory spoke pluck test to see if your tensions are in the ballpark.

16. Ive built somewhere around 100 wheel sets, almost all to 130 kgf, some to 120 kgf. The stress relieving process adds a crapload of tension on top of that, very easily another 20kgf. Ive never stretched a single spoke. Some dynamic loads from riding should exceed 150 kgf as well.

Something crazy is going on with your spokes.

17. Originally Posted by One Pivot
Ive built somewhere around 100 wheel sets, almost all to 130 kgf, some to 120 kgf. The stress relieving process adds a crapload of tension on top of that, very easily another 20kgf. Ive never stretched a single spoke. Some dynamic loads from riding should exceed 150 kgf as well.

Something crazy is going on with your spokes.
Is your spoke tension ever lower after stress relieving?

Why do people stop at around 140 kgf? My recent experience is that you just can't seem to get it any higher, and you don't quite realize that it's 'cuz you're at the yield limit.

It would seem the reason that 130 kgf -140 kgf is the max that people tension their spokes to is because it is the max they can tension their spokes to, because another quarter turn of the nipple just doesn't seem to do anything, except push the spoke another 0.1 mm through the nipple. You don't really realize you're at the yield limit unless you just keep going twisting the nipples, and then you are just stretching them .45 mm per complete turn; a complete turn at that point is a lot of turning, but .45mm doesn't look like much. The spokes don't snap or anything.

This makes the most sense. Nobody reports that they get more tension in their spokes than around 140. Although I saw someone say 169 somewhere, but there are straight gauge spokes, too.

Seriously, think about that. You'd occasionally have builders say they were building at 200kgf - if they could, and what with carbon rims and fat bike rims, you probably could if the spokes could do it. But do you have people reporting that? We've got various strengths of nipples, spoke wrenches that grab all 4 sides, hex nipples that can be turned with a socket. Every top builder says they go to 120 to 140 kgf, not "but if I have a carbon rim I go to 200 and use the strongest nipple available". "Good enough" arguments are fine and all to explain most people's reasons, but you'd still expect some outliers, some people who take it to the extreme. I mean it's the frickin' internet. Something like: "I have a carbon rim with eyelets, titanium nipples, a spoke wrench that grabs all 4 sides, and I take it up to 250 kgf".

A quarter turn of the nipple is only about 0.1 mm of spoke stretch, and if you're at a point where you just can't get the tension any higher, you might not even notice that you hit the yield point. And maybe stress-relieving is just stretching (plastically) the spokes just a teeny bit so that they get below the yield limit (i.e. trade some plastic stretch for some elastic stretch), which might result in them have a higher fatigue strength.

And what does the ultimate tensile strength matter? As long as it's higher than the yield strength. We can correlate the ultimate tensile strength with an amount of cold working and then calculate a yield limit? Maybe someone with a sapim spoke could see if they can get it over 150kgf. If it matters ... It does seem like this is an interesting piece of information that has been missing. The yield strength is certainly much more important than the ultimate tensile strength, which is talked about on occasion.

I don't know why I'm arguing these points. I guess it just seems like this is an important thing to know, somehow. And people are saying it can't be true that the yield strength of the spokes is so low.

I challenge someone to take a 14/15 spoke above 160 kgf.

I could have counterfeit spokes or something, but everything is pointing toward: the yield strength of these spokes is somewhere around 150kgf.

18. Originally Posted by beanbag

BTW, you can easily calibrate your spoke meter by hanging a wire off a ceiling beam, and putting your weight onto it. Then use the tension meter on this wire.
Any old wire?
Actually I'd have to use the spoke, this Wheelsmith meter isn't agnostic to spoke diameter.

19. Was there any observable deformation to the diameter or shape of the elongated spoke?

urmb

20. Originally Posted by Godlikedog
Any old wire?
Actually I'd have to use the spoke, this Wheelsmith meter isn't agnostic to spoke diameter.
Yes it is. Do you have the instructions for it?

You are supposed to hold the meter against the spoke (or any old wire), and have the measuring plunger thing touch the spoke, but NOT the spoke-bending-in-the-middle-thing. Then you rotate the outer diameter of the indicator so that it reads zero. Then you let the spoke-bending-in-the-middle-thing touch and deflect the spoke, and THEN you read the number off the dial.

I think you should get your meter working right before you start quoting numbers for spoke tension.

21. Originally Posted by beanbag
I think you should get your meter working right before you start quoting numbers for spoke tension.
Well, I can't argue with that.

Here is a picture of the meter and the calibration sheet that came with it. Looking at other pictures of calibration sheets for this model of meter, it seems that my measurement of 73 corresponds to somewhere in the neighborhood of 130-160 kgf, that's where I got the numbers. And I know mine can't be that far off from that, because if the spring was weak from age, it would just score lower numbers, and I have measured some other wheels that I didn't build, and the drive side spokes measured in the 60's. I'll take the wheel to my LBS tomorrow and see what they measure the tension as.

22. Oh sorry, I was thinking of the Jobst Brandt FSA tensiometer, which I thought was wheelsmith but now I see it is a different kind.

In that case, find a wire with a diameter close to your spoke diameter.

23. Originally Posted by urmb
Was there any observable deformation to the diameter or shape of the elongated spoke?

urmb
The center of the spoke does seem to be about .01 mm smaller than a fresh spoke. It's hard to get an exact measurement, but after averaging ten measurements for each, here is about a .01 mm difference, 1.754 vs 1.763. When holding both the spokes in the calipers at the same time, it is clear that the longer one is skinnier because it slips down - the calipers don't grip it.

24. Wow. What sort of rim are you using that can handle such tensions without tearing the nipples out? What do your spoke holes look like? Any deformation?

25. Originally Posted by Godlikedog

Why do people stop at around 140 kgf?
Because the rim would collapse.

26. Originally Posted by One Pivot

Something crazy is going on with your spokes.

I agree. Try some different spokes.

27. Originally Posted by Godlikedog
Is your spoke tension ever lower after stress relieving?
Yes, but only once. The first round of stress relieving drops the tension 10 or 15 kgf. I attribute this to the elbow bending and settling into the hub. The second+ round of stress relieving doesnt drop tension unless a spoke is wound up.

If your conclusion was true, stress relieving a wheel built to 130 kgf would drop the tension every time. Or simply riding it would drop tension every ride. This never happens.
Why do people stop at around 140 kgf?
As someone said, because the rim would collapse. 125kg is a pretty standard max tension for the rim. Overtensioned rims get wobbly and dont last.
It would seem the reason that 130 kgf -140 kgf is the max that people tension their spokes to is because it is the max they can tension their spokes to
.Nobody reports that they get more tension in their spokes than around 140.
They'll definitely go higher. A lot higher. It'll ruin your nipples or rim though. Theres been lots and lots of reports of poor builds way over 140. Its a bad build though, ~125 is the max tension you want to use unless you've got proprietary spokes.

28. Originally Posted by TigWorld
Wow. What sort of rim are you using that can handle such tensions without tearing the nipples out? What do your spoke holes look like? Any deformation?
It's a Surly Rabbit Hole (50mm wide). The nipples certainly have dug in to the rim, but no deformation otherwise.

29. Originally Posted by One Pivot
If your conclusion was true, stress relieving a wheel built to 130 kgf would drop the tension every time. Or simply riding it would drop tension every ride. This never happens.
Once you've stress relieved it, it has dropped tension and is now not at the yield point anymore. Stress relieving it again might not bring it past the yield point again, so the tension wouldn't change, because you wouldn't plastically stretch it.

The fact that it does lower tension when you do it once is evidence that you are taking it past the yield point when stress relieving.

And I don't think riding a wheel causes tensions to rise. I think the highest spoke tension the wheel ever has are when it is in the trueing stand.

30. If a spoke yields at 150 kgf, it will plastically deform any time it hits that limit. After stress relieving the wheel is retensioned up to 130 kgf and stress relieved again. It doesnt drop tension or plastically deform the second time is what im saying, despite being taken to the same tension during stress relieving again.

The tension drop is from the spoke settling and being destressed. You dont get that big drop again.

Your experience is pretty interesting, I have no idea how you got that crazy amount of stretch, but you should definitely know that no one else is getting that! Thats assuming your tension meter is reading accurately and all this really is happening at those tensions.

31. I once calculated that the increase in spoke tension is about 3x the squeeze force.

32. Originally Posted by Godlikedog
...I have figured it out, and it is that my tensiometer is not in kgf. Looking for a photo of the wheelsmith tensiometer I noticed that they come with a calibration sheet, which I must've lost a long time ago...
I trust that you found the exact calibration sheet for your tensionometer, because each Wheelsmith tensionometer has their own calibration sheet. You can also send them back to Wheelsmith for re-calibration.

Tip, make a copy of your calibration sheet, cut it out, and glue it to the inside lid of the tensionometer box. That way the sheet is always with the tool! Advanced tip, highlight the desired tension numbers for each spoke profile, so at a glance you can easily see what reading you need.

33. Originally Posted by beanbag
This thread should serve as a reminder that you should do a cursory spoke pluck test to see if your tensions are in the ballpark.
On my front wheel, the disc side goes ding, the non disc side goes dong.

Is that right?

Do I have a good ding dong?

34. You either have to measure your ding dong or compare it to other ding dongs at the bike store.

35. ## How do get such high tension in your spokes?

Originally Posted by Godlikedog
It's a Surly Rabbit Hole (50mm wide). The nipples certainly have dug in to the rim, but no deformation otherwise.
No deformation yet.

36. Well, I tested my spoke tensions on a calibrated spoke tension gauge at my LBS. They were mostly in the 160's, one was 172, and a couple in the 150's. I measured 16.

I tested one more fresh DT spoke from the box and got it up to 175 before it started stretching and would not get to any higher tension, i.e. it hit its yield limit.

The next step is to test other spokes. I have a wheel built with 14/15 Wheelsmith spokes, so I tested one of them. I removed the nipple, installed a hex brass one, and cranked it up. It got to 173 kgf and then no more - many more twists, full complete twists, with an electric drill, and no higher tension, in fact it went down a little, until the nipple gave way.

So, here it is:
the yield strength of the 14/15 spokes we use is around 175 kgf.

If you are familiar with hardened steel wire, like piano wire, you'll know that it is hard to bend, I mean to deform. Spokes are easy to deform. Compare a 2mm piece of piano wire to a spoke. The spoke is much easier to deform, this is the same thing as saying the yield strength is much lower. And I think we want them this way. I don't know if I'd want a wheel built with piano wire, even if it were rust proof.

I haven't tested Sapim spokes. But I doubt they're different, because I think this is how spokes are supposed to be. I'll explain:

If I were a spoke engineer, I think the goals would be to:
(1) maximize fatigue strength*, and
(2) aim to get yield strength above what is needed for high tension wheels, but keeping ductility as high as possible. High ductility means low yield strength. So, I would want to get the yield strength as high as is needed, but no more, i.e. slightly above that needed for high tension wheels.
*[I think I might not be using this term correctly, but I mean durability.]

Why do we want it to be ductile?
Don't we want them conformable to some degree?
I think it's safer, if the spoke is ever exposed to an extreme stress, it will just stretch, it takes a great deal more energy to break a ductile material than a non-ductile one (this energy is the area under the curve on a stress/strain graph, which is much bigger for a ductile material than a brittle material).
It prevents people from getting out of line with spoke tensions.
Their easier to manufacture.
And I don't think stress-relieving would have much effect on piano wire. (I suspect this last one might be the biggest reason, the metallurgical reason).

Now, some people (e.g. Jobst Brandt) say that if stress is more than 1/3 of the yield strength, fatigue life is greatly diminished. After seeing a metallurgist ripping him a new one on alt.bicycles.tech at google groups for his lack of metallurgy knowledge and metal fracture knowledge, I decided I needed to look this up.

From Metal Fatigue

"Experiments have shown little direct relationship between the fatigue limit and the yield strength ,ductility etc. However some relationship between the fatigue limit and the tensile strength Su has been established for unotched polished specimens tested using the rotating beam method."
[copied and pasted]

You can understand why spoke companies don't tell you this. Your average spoke consume probably doesnt distinguish much between ultimate tensile strength and yield strength (I know I didn't until recently, and I know a lot more about this stuff than anybody else I know, (but I don't know that many people)), and it would be easy for a company to say "our spokes have a tensile strength of 180,000 psi, but the yield strength of our competitors is only 90,000 psi" or some other manipulation of the facts. On Wheelsmith's web site they say they make the "ideal spoke", not the strongest, but ideal. It's nice and clear to be able claim that you make the strongest thing, and give some numbers, but you get into muddies waters when your claims are about the best compromise.

If you don't believe me, I urge you to try for yourself to get a 14/15 spoke tension over 180 kgf.

----------------------------------------------------

I decided to do some testing on a fresh spoke to get some data. I installed it and got it up to a mild tension, then turned the nipple 360 degrees (I put a post-it on the spoke and compensated for spoke wind up) and recorded the tension. Then I repeated it, and repeated it, ...

The results were:
Start. 61 kgf
+1 turn 90
+2 turns 113
+3 turns 137
+4 turns 163
+5 turns 171
+7 turns 175
+8 turns 170
+9 turns 171

37. That other guy with the tensile testing machine got them up to 325 kg, so either you or he is a liar.

38. No time to go through this entire thread right now, but interesting and I'll be back tonight to go through it, but just wanted to share my quick \$0.02

I switched to DT Swiss Comp spokes must be 5 years ago and I've never had a problem building up wheels and having them stretch and I usually build to around 120-130 Kgf unless building Stans rims where I keep it under 110 for Flows and 100 for Crests. I think you better find you conversion sheet for that meter, I think you'll find your "70" translates into a much higher tension that the sheet you posted lists if you're managing to stretch spokes OR you've got a bad batch or knock off spokes. Have you by chance bought another set of spokes to test and see if you get the same results?

39. Originally Posted by Godlikedog
Are people able to get over 110 kgf in their revolution spokes?
I once put a Revolution spoke in an old wheel to see how high I could get the tension, because I did hear they stretch out before they can get to the proper tension for the drive side of a rear wheel/disc side of a front wheel. I managed to get it up to 180 kgf without any permanent elongation (and then gave up trying to twist the nipple).

Since then I've build up a set of 27.5" mountain wheels for myself with Revolutions on them at 120 kgf. Only maybe 90-100km on them so far but they have taken some drops and done some dirt jumps and seem fine.

40. In short, even with the OP's data, normal wheels built normally, dont have any problems with elongation or ever get close to yield. With everyone elses data, we're SO far away from yield that its a non-issue. Even 170 kgf is insane high tension beyond what any rim specs.

41. Add to this the fact that higher tensions (like beyond 120kgf) do nothing in the way of building a better wheel and we've arrived at a serious non-issue. Interesting, but a non-issue for a properly built wheel.

42. Originally Posted by TigWorld
Add to this the fact that higher tensions (like beyond 120kgf) do nothing in the way of building a better wheel and we've arrived at a serious non-issue. Interesting, but a non-issue for a properly built wheel.
OP here, yes it is a non-issue. I found it interesting how it doesn't seem to be known, yet the level of discourse on bicycle wheels seems so advanced sometimes.

As for the guy who tested the spokes and got 325 kgf, that was probably the ultimate tensile strength. My understanding is that as they stretch they get strain hardened and increase in strength. If they didn't, I don't see how yield strength would be different from ultimate tensile strength.

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