cyccommute 

Please understand that I'm not saying the forging process doesn't add strength. It does. Cold forging, i.e. smashing a cold metal part into a form, has long been known to increase the strength of a part. I even agree with FBinNY about the mechanism. I even agree that there may be some benefit from ovalizing the spokes like Sapim does but the benefit isn't strength...it's aerodynamics.

Working the spokes like Sapim does adds strength at the middle of the spoke. Spokes seldom break at the midpoint of the spoke. They seldom break at the nipples. They break at the elbow. Spending money, time and effort on strengthing the middle of the spoke is wasted. Increasing the diameter of the head also increases the strength of the spoke but it does so at the place where it actually does some good.

Alias530

So the Lasers are considered too light duty for my weight, but what about CX Rays? Is the forging process enough of a strength adder? Or am I better off with DT Comps for a little more weight?

cyccommute 

I'm confused as to what you are looking for. The Lasers may be too light duty for your weight, although that depends on how you ride. You seem to want the CX Rays which is fine but buy them for the aerodynamics rather than strength.

The triple butted spokes I've suggested above, by the way, are only marginally heavier than a regular double butted spoke. A tiny part of the head of the spoke is thicker but the weight difference is negligible. Based on the increased volume and the density of stainless steel, a triple butted spoke with a 2.3mm head is a whopping 2.5mg heavier per spoke than a 2.0mm spoke. There are 1000 mg in a gram so you'd need 400 spokes to add 1 gram of weight to the wheel. If you need to build wheels with 400 spokes, you got other problems

All kidding aside, a 50% increase in strength for a 2.5mg increase per spoke in weight is a damned good bargain.

Alias530

I'm under the impression that the CX Rays are strong and light, that's all I'm looking for. Unless I'm missing something, they have the strength of a heavier spoke, with the weight of a Laser. That is the only reason I'm looking at them. Cost and aero don't matter to me. I read an article about CX Rays vs Lasers last night and the aero savings was 1 watt, which is irrelevant in my eyes. But if they aren't strong with a long fatigue life, I'll just accept the weight penalty with something heavier.

FBinNY 

There's strength and there's strength. As my friend pointed out earlier, adding strenght to the middle won't directly change the practical strength because spokes don't fatigue and break there. Spokes break at the elbows and those are unaffected by the cold working at the center.

What the added strength does is increase the yield and tensile loads the spoke can handle. That means the wheel can be built tighter, which is important in thin section spokes.

But heavy riders have to consider wheel flex, lighter spokes allow more lateral flex. This works the elbows more since the short leg is held steady while the long leg is flexing side to side. More flex means shorter fatigue life which is exactly what Sapin is telling you.

I'm not invested in how you build your wheels. But you're here for advice, and seem to resist the simple notion that wheel/spoke strength should somehow be proportioned to the load, and that heavier riders shouldn't be riding the same stuff as lighter riders.

So you have the opinions, sort them out then stop obsessing over every detail and build yourself a set of wheels. You can go max. light and if they don't hold up, make adjustments next time. Or you can take the weight penalty in the hopes of longer service life, and if they hold up wonder if you might have saved another few grams.

Alias530

I'm not resisting it, I'm just trying to sort out the point at which I'm underbuilding the wheel. I've accepted that Lasers are too light duty. I'm trying to sort out whether Sapim's process to turn a Laser into a CX Ray will allow me to use a lightweight spoke that is also strong, by paying more for it.

I've always been under the school of thought that out of strong, light, and cheap, you could to pick two. I'm picking strong and light. That's what the CX Rays seem to be. I'm just trying to make it clear that if their benefit is aero, NOT strength, that I'll go with something else. I just don't want to turn a 1,500g wheelset into a 1,700g wheelset by overbuilding it, because the benefits compared to what I already have will disappear.

chaadster

Yes, I understood all that, I just question how you know it. How are you sure the forging is wasted strength?

As I said before, and which you have not addressed, is that it stands to reason that the forging process brings about behavioral changes throughout the spoke. The shaping and metallurgy changes will impact the way stresses are distributed and the way the spoke moves and transmits vibration.

I don't know what the answers are, and I'm not saying you're wrong, just that my base for trust on these matters are the manufacturers, the folks who've presumably done modeling and testing of spokes, though a critical questioning of that base trust by some dude in an internet chat room could be compelling were it comprehensive and supported with some facts or other evidence.

Certainly your basic question is valid-- does spoke body forging provide practical strength?"-- but I just don't see any rational reason to answer in the negative. It may be that forging does nothing for strength at the J bend, and the manufacturers are referencing other elements of spoke performance as stronger, but I'd just like to hear a little more before tossing out their strength claims as meaningless or irrelevant.

FBinNY 

This is a nice saying that has been around for years and has some degree of truth.

But you cannot buy your way past physical realities. If you could, then building longer bridges across wider spans would simply be a question of spending more dough.

I and others have explained how strong for the weight, or stronger still does not equate to strong in an absolute sense. Last thought - If Sapim thought that their lightest spokes could be as strong as their heaver spokes, why would they offer so many heavier spokes?

BTW- if you came to me to have these wheels built, at this point I'd refuse the work. The reason is that I have two choices.

1- build what you want and gamble that it holds up. May be OK for you, but not good for me as a builder.
2- build what I think will work, and even if it holds up, you won't be happy because you'll always suspect that we could have gone lighter after all.

You're in basically the same position, so I suggest you disregard everything I and others have said here and build what you really want. If it doesn't hold up you'll make an adjustment next time. Otherwise, you'll never know if you could have built those light dream wheels.

As they say, it is better to have loved and lost than to never have loved at all.

chaadster

That's exactly the claim that I challenge.

This discussion is formed around the idea that strength only refers to J bend fatigue, which is erroneous. The entire spoke is forged anyway, so really it's the way that the additional shaping and increased density of forged aero section spokes affects overall performance that's the issue, not a matter of forged vs. non-forged.

There are many types of forces that impact spoke performance, and increased strength can manifest in other areas than the elbow. Reducing the intensity of stresses that the elbow sees is a way to increase fatigue life without changing the fatigue limit of the metal at the bend itself.

FBinNY 

Unless Sapim somehow works the elbow differently than they do with all their other spokes, there won't be any difference in these elbows as compared to all the others. More cold work in the center of the spoke doesn't magically change the elbows.

Bill Kapaun

DT Competitions come in 14/15 & 15/16.
You could go "all Competition" and still be using 2 different spokes.

My typical choice is to use "All Competitions"-
14/15 DS & 15/16 on the rest.
Easily available here in 1MM increments-
DT Swiss Components | The Colorado Cyclist

They aren't the cheapest at this vendor, but you can mix & match to exactly what you need.
When you compare the total weight to aero spokes, for the entire build, you may be pleasantly surprised.
Note you need to get 15 ga. nipples for the 15/16's.

cyccommute 

You are really over-thinking this. You can easily do the math to determine how much more or less a spoke weighs based on it's diameter. Calculate the cross sectional area and multiply by the length to get the volume of steel that is used. Then divide by the density of the steel...8g/cubic centimeter... and that will give you the weight per spoke. But, honestly, the weight difference between spokes is going to be minimal. You aren't going to gain 200g/wheel by going to a slightly heavier spoke. As I said above, the difference is on the order 2.5mg/spoke for a heavier head. You have to do something else to the wheel to gain 200g.

Honestly, it's tough to lose 200g of weight on a wheel. I recently built a wheelset that lost 2 lb (about 1000g) on both wheels but that's with a light rim (Velocity A23) and light hubs (White Industries T11). A good chunk of the weight savings came from the titanium freehub body.

The forging that is being done to the CX Ray spoke is only in the middle. Nothing is done to the head of the spoke over what is done to other spokes. Forging and working only have an effect at the site where the forging occurs.

Spokes aren't "forged". They are drawn from wire stock. Sapim goes a bit further and makes the middle of the spoke oval by compressing the spoke. If anything the ovalization of the spoke may increase stiffness which translates into more force being put on the head. The spoke may be less elastic than a traditional double butted spoke.

Exactly.

And when FB and I agree on something, you should take it as a miracle...a Christmas miracle if you like

chaadster

I should have been clear that I was referring to the spokes being discussed, i.e. butted spokes, all of which are forged in a swaging process.

DT Swiss, however, claim that all of their spokes, even straight guage, are forged: To the Point - DT Swiss Talks Spokes - Pinkbike

Anyway, you clearly don't want to address the questions I raised about your theories, and appear to be set on believing whatever it is you want to believe independent of critical examination, so I'll leave the discussion with you at this point. I've clearly stated my concerns about your speculations, so at least there is an alternative narrative for others who want to consider these questions.

chaadster

That's right, but can mechanically change what happens at the elbows.

cyccommute 

Sapim makes the same claim about their butted spoke as they do about their CX Ray which is what can be claimed about any butted spoke. Although all manufacturers claim different methods, I suspect that they all use similar techniques with similar results. Pillar is one of the few places where I've seen actual values for breaking strength. The 2.0mm straight gauge spokes break at 270 kgf. The 2.0/1.8/2.0 spokes break at 290 kgf. For comparison, the 2.2/1.8/2.0 spokes break at about 320 kgf. That says to me that butting the spoke adds strength but adding more beef to the head does even more.