Bicycle Mechanics - black spokes break

"black spokes break

and black spokes creak"


true or false or somewhere in between?

are they anodized? are they dt spokes, or disposable wheel spokes?

among the people i know who build wheels and have experience in general, black spokes are regarded as detrimental to a wheel. mainly because of the crosses - squeeze the crosses on a silver spoked wheel and they slide and flex easily over each other and return to their original position, with black spokes, the drag and bind over one another, and dont return to their original position unless seperated by hand, the creeking you may be refering to are the spokes occasionally popping back into place after theyve 'walked' over to one side.

all my builds are done with silver spokes, unless the customer asks otherwise - by all means black spokes arnt weak by any means, but when working on a wheel things feel alot more refined and secure when the spokes are silver...

hi quality like dt or wheelsmith

Interesting, my ATB (Trek 820) is about a year old (used for commuting) and i've started hearing a funny creak from the front wheel if i'm in a strong wind. Could be the black spokes rubbing on each other?

Does this mean the wheels need truing? I check them when I do my weekly inspections and haven't noticed them going out of true. Only broke one spoke in 1 year, and that was because I was hauling too many books.

among the people i know who build wheels and have experience in general, black spokes are regarded as detrimental to a wheel. mainly because of the crosses - squeeze the crosses on a silver spoked wheel and they slide and flex easily over each other and return to their original position, with black spokes, the drag and bind over one another, and dont return to their original position unless seperated by hand, the creeking you may be refering to are the spokes occasionally popping back into place after theyve 'walked' over to one side.

I tend to keep a bit of lube on the spoke crossings for this very reason...

I give a 1 year spoke breakage guarantee on all my handbuilt wheels.....except if you want black spokes. I find them to be more brittle at the elbows as well.

I see the black spokes fail far more often then plain SS spokes. The worst is the straight 15g unbranded spokes that come on just about every MTB these days.
A confession: I did build up my singlespeed with black 14/15 Dts because I wanted an all black/flat silver bike. So far so good.

I just checked our three, late model MTBs. Only one has black spokes. Naturally, it's the newest and most expensive.
Should I put lubricant where the spokes cross? If yes, what kind of lubricant? This bike is taken on trails, I'm concerned about dirt build up on any unprotected, lubricated surface. Thanks for any feedback.

I just checked our three, late model MTBs. Only one has black spokes. Naturally, it's the newest and most expensive.
Should I put lubricant where the spokes cross? If yes, what kind of lubricant? This bike is taken on trails, I'm concerned about dirt build up on any unprotected, lubricated surface. Thanks for any feedback.
I think that lube where the spokes cross would be counterproductive, especially for a mountain bike. Collected grit will make things worse, not better. Is my guess, at least. I've never had a bike with black spokes myself.

I think that lube where the spokes cross would be counterproductive, especially for a mountain bike. Collected grit will make things worse, not better. Is my guess, at least. I've never had a bike with black spokes myself.
That makes sense to me, especially with the type of riding I do. I'm just going to ride the bike. If I start to have spoke problems, I'll remember this thread and rebuild with silver spokes. Many thanks to the OP for sharing this info.

That makes sense to me, especially with the type of riding I do. I'm just going to ride the bike. If I start to have spoke problems, I'll remember this thread and rebuild with silver spokes. Many thanks to the OP for sharing this info.

That is just what I reccomend. If you break one, replace the spoke. When you break the second one, build the wheel.

Anyone have anything more than anecdotal evidence? so far I am seeing the "black spokes are inferior" thing in several ways:

1. For the same rim, hub, lacing, and spoke size, black spokes will break or creak more when subjected to the same uses/stresses.

2. There are proportionately more black spokes of all uses and applications on the market, so a greater percentage of spoke problems involve black spokes.

3. Black spokes are used more often in low-end applications, so we see them with problems more often.

4. Black and silver spoke problems occur at the same frequency proportional to application, we just take notice of it more now that we have the idea in our mind that black spokes might be worse.

I have no evidence, but it seems that only case #1 would mean that black spokes are actually more prone to problems. Am I thinking this through correctly?

I'm no expert on this subject, but I can't help but think this is the stuff urban legends are made of.

Bob

Jimmythefly has a very logical mind.

+1

I have not noticed any more problems with black spokes than silver.

Black spokes are anodized, and that's where the problem lies. Here comes the science (sorry);

Spokes, even DT Swiss, who claim they 'cold forge' them, as if drawing isn't cold-forging, d'uh, are heavily drawn, much more so than frame tubing, bar-ends, etc. They come from ~10mm stock, as a rule and undergo massive deformations. While this degree of cold-work makes them very, very strong, it obviously can't alter their Young Modulus. It won't make them stiffer, as that is a fixed material parameter, so even at much higher strength, they elastically deform the same amount as unworked material.

Now, spokes are generally made from 18-8 (304Sxx) stainless steel, of varying cleanliness. The degree of impurity, inclusions, unwelded voids, etc - the quality, is what affects the base material price, and so, to some degree, the final quality and price.

The highest quality ones generally come from manufacturers with the highest care and attention to detail, quality control installation. This is reflected in the accuracy of the cold-heading an manufacturer's mark on the head, the forming of threada nd the smoothness of the spoke surface.

It is this surface finish that is of paramount importance in the case of spokes in general, and black spokes in particular.

Anodising is, as most of you appreciate, an artifical thickening of the natural oxide skin of a material, brought about by electrolytic means. This however, unfortunately, unlike for example, stove-oxidising, a process seen in heat-treatment of ductile iron pipe means the oxide film is now also porous at its outer extremeity, and so will uptake dyes.

This is in general in a highly-worked, very strong material, a Bad Thing™. 304 stainless is very ductile when unworked, or annealed. At more than 90% reduction, it only has ten percent or less ductility remaining. This is more than most aluminium tubesets will offer, but more importantly, the absolutely massive impact toughness and resistance to crack propagation have been drastically reduced by all the locked up dislocation substructure (cold working).

Even the tiny elastic deformation that the unworked material could comfortably and unendingly absorb has a much more severe effect on hard-drawn material. Fatigue failure occur via what is termed microplastic deformation - tiny local stress concentrations vastly exceed the fatigue limit and yield stress, while remaining in the bulk sample comfortably under the yield limit. And in spokes, this adds up quickly.

As long as the surface is perfect, the likelihood of such micro-plastic deformation, due to miniscule stress concentrators is slim. Add a porous, incredibly hard (oxides tend to be), brittle layer, intimately bonded to a hardened, less tough substrate = recipe for sudden failure. Fatigue failures ALWAYS occur at the surface.

In short:

Blackened spokes, of ANY quality have an inherently higher likelihood of failure. BUT. Most good quality spokes will not come close to their fatigue limit or suffer sufficient stress for a crack to occur in the surface.

As long as the surface is perfect, the likelihood of such micro-plastic deformation, due to miniscule stress concentrators is slim. Add a porous, incredibly hard (oxides tend to be), brittle layer, intimately bonded to a hardened, less tough substrate = recipe for sudden failure. Fatigue failures ALWAYS occur at the surface.This is the exact reason anodized rims have fallen out of favor. Adding a super-hard non-flexible layer on top of an underlying softer flexible material will eventually cause surface-cracks. Which propagates through and eventually cracks all the way. Spokes are stressed closer to yield and ultimate strength levels than any other part on the bike. So there's already some stretch in the material under tension, making surface-cracks that much easier to develop.

Black spokes are anodized, and that's where the problem lies. [snipped]

I thought black spokes were painted that color, but just looking at some black spokes that I have here (DT Swiss) makes me think that maybe they are anodized (just going by appearance). I was under the impression that anodizing was almost exclusively an aluminum surface treatment. Do you know for a fact that stainless steel spokes are commonly anodized?

Also, I understand that there are two basic types of anodizing treatments: cosmetic, and "hard". If my DT spokes are indeed anodized, they appear to be only cosmetically treated instead of hard anodized. The coating comes off fairly easily and doesn't seem to resist abrasion much at all. This would lead me to believe that the treatment wouldn't impart surface imperfections to the underlying material.

*Nods*

We should sit down over half-caff one day and set the materials engineering world to rights.... :)

Fatigue failures ALWAYS occur at the surface.

I disagree. Impurities in the metal can cause stress risers too.

I disagree. Impurities in the metal can cause stress risers too.


No. They can't. Impurities are nothing more than statistical abberations in the lattice. Manganese atoms in maraging steels are impurities. Sulphur in any steel is an impurity, but unless those impurities cluster and become an inclusion, they alone will not exert enough effect to cause a failure. Inclusions and other point defects (voids/vacancy clusters, dislocation clusters forming ithe beginnings of cracks, gas bubbles) can however. The terminology is very explicit in these cases for a reason, and that reason is not to trip you up, but to ensure that the phenomenological situation is correctly ascribed.

Stress raisers in a material require dislocation pileup. One single impurity atom cannot cause a dislocation pileup because it has no way of hindering the dislocation line. Multiple clusters of impurity atoms that therefore are inclusions, however can, by a variety of means, most usually Orowan dispersion strengthening.

This isn't open to disagreement. It's basic materials mechanics and dislocation theory.

EDIT:

And as for the fatigue reference, fatigue failures occur at the surface of a component for a reason - because the surface of a component is always under the most stress - it has environmental stress-corrosion cracking effects, the greatest distance and therefore bending moment incurred from the 'free surface' of zero net stress, and no material ahead of it to share the greatest loading - as well as a distroted, not-even-close to perfect lattice in the surface region.

No. They can't. Impurities are nothing more than statistical abberations in the lattice. Manganese atoms in maraging steels are impurities. Sulphur in any steel is an impurity, but unless those impurities cluster and become an inclusion, they alone will not exert enough effect to cause a failure. Inclusions and other point defects (voids/vacancy clusters, dislocation clusters forming ithe beginnings of cracks, gas bubbles) can however. The terminology is very explicit in these cases for a reason, and that reason is not to trip you up, but to ensure that the phenomenological situation is correctly ascribed.

Stress raisers in a material require dislocation pileup. One single impurity atom cannot cause a dislocation pileup because it has no way of hindering the dislocation line. Multiple clusters of impurity atoms that therefore are inclusions, however can, by a variety of means, most usually Orowan dispersion strengthening.

This isn't open to disagreement. It's basic materials mechanics and dislocation theory.

You're right. It was inclusions that I was thinking of. Materials science was a few years ago for me. Thank you for the clarification/correction. :o

Sorry, chap. I came across as really arsey on that one...

Sorry, chap. I came across as really arsey on that one...

No worries, I'm fairly thick-skinned. :)

Any input on my earlier post (#19)?

'Hard' anodizing is a bit of a misnomer. There were in the beginning two ways of anodizing, but almost all now use the method that was originally used as 'hard'. It involves a DC current and a big H2SO4 bath. The 'soft' method used hydrated chromic acid (C2SO3(aq)) and has almost totally fallen out of favour. Effectively all aluminium alloy anodizing now uses the hard method.

Now, this is the important bit - Alumina (Aluminium oxide... it's great how you can just name the oxide of a metal by knocking off the 'um' and replacing it with 'a', innit?) lattice-matches with aluminium. It takes up exactly the same amount of space as the aluminium alloy lattice. At ambient temperatures it has exactly the same thermal expansivity, and self heals anyway, so at room temperatures and neutral pHs it won't break up. Alumina, for a ceramic, is dense and tough and extremely hard. It won't spall off the aluminium without a great deal of effort. It is chemically bonded within its own atomic structure and to aluminium.

The partially adsorbed (not absorbed) surface oxide compound/solution layer on most stainless steels is a different matter. Even pure chromium oxide is not anywhere near as hard or strong as alumina, nor does it lattice match with the substrate as stainless steels are obviously not in the majority, chromium.

You can anodise any metal that forms an oxide surface layer, including but not limited to; titanium, lithium (not recommended!!), beryllium (even less so), , magnesium... Titanium components can be dyed the same way as aluminium ones, althought he surface film is not so hard as alumina, either.

How are you takign the coating off the spokes - with a piece of steel/coin?

Thanks, Falanx, for lots of information here. It's been 7 years since I've touched any of this, theory- and textbook-wise. I study people now.

i use black DT Supercomp triple butted spokes and have had absolutley NONE of the problems presented forth on this thread

[snipped excellent background theory] The partially adsorbed (not absorbed) surface oxide compound/solution layer on most stainless steels is a different matter. Even pure chromium oxide is not anywhere near as hard or strong as alumina, nor does it lattice match with the substrate as stainless steels are obviously not in the majority, chromium.

This being the case, does the oxidized layer on a piece of anodized stainless steel make the material significantly more susceptible to developing surface imperfections that develop into stress risers? It doesn't sound as though the process has the same negative effects on stainless as it does on aluminum.




You can anodise any metal that forms an oxide surface layer, including but not limited to; titanium, lithium (not recommended!!), beryllium (even less so), , magnesium... Titanium components can be dyed the same way as aluminium ones, althought he surface film is not so hard as alumina, either.

Interesting. I had heard of anodizing stainless before, but didn't realize you could anodize any metal that develops an oxide layer (makes sense though).

But again, do you have any reason to believe that black spokes are anodized?




How are you takign the coating off the spokes - with a piece of steel/coin?

Yes, with only fairly light rubbing of a steel house key. I'm not seeing any bits of residue coming off as I would expect with a painted part. In addition, the surface coating appears to be extremely thin.

You're clearly very knowledgeable on this subject, and I appreciate all your input. I've learned a lot.

Sorry, yes, missed that bit:

To get sufficient opacity on a layer of paint, especially black, you need a coating thickness of at least 150 microns, or just over one eighth of a millimetre. This is going to interfere with spoke bedding when building. Not because they won't fit, (I've not gone mad, don't worry) but because the paint will collapse and disintegrate at the head root, making them float on a layer of paint. Coupled to that, that kind of loading will cause paint weld-on to the hub. I don't think I've ever seen paint transfer from black spokes...

Second, it would actually be cheaper to anodise them - indeed, stainless wouldn't even need a current supplied to the spoke to artificially oxidise them further, as passivation electrode potential of 304 type means it oxidises quicker than aluminium. Dunk, dye. That simple.

Anodising coatings can be defined right down to 5 microns. Heavy duty coatings tend to be up to 25 microns.


Right - this needs some clarification. I tried not to make what I was submitting too dry, so I didn't expand fully. While the chromium oxide/chromium-iron-oxide/etc layer on the surface of a length of hard-drawn stainless steel is not so hard as alumina, and the substrate is harder and stronger than aluminium alloys (so the hardness oxide:hardness substrate ratio is not so large) it is still harder and brittle. The effect is not so great, but as we've all discussed, the spoke is the most highly stressed piece of material on a bike - the normal windup tension of a spoke reaches 440MPa (according to Smallman et al.). That's greater than the UTS of 6061 and just under the yield of most of the highest strength aluminium alloys. In such a highly stressed piece of equipment, the difference doesn't have to be so great to have an effect.

In other words, what you lose in 'greater strength and toughness with 'softer' brittle, hard coating', you gain in 'most intolerant component to damage'.

Fascinating! Thanks for all the explanations, though I'm not sure if this discussion has clarified things for me or only made them murkey in new and exciting ways...

Slight problem with all of this: anodizing is dyeing a layer of aluminum oxide. Steel spoke can't be anodized, as they have no aluminum oxide, and iron oxide is simply rust. They can have a black oxide coating tho.

Blackened spokes, of ANY quality have an inherently higher likelihood of failure. BUT. Most good quality spokes will not come close to their fatigue limit or suffer sufficient stress for a crack to occur in the surface.

If you'd like to wax eloquent about all manner of spoke related things, like: stress relieving, fatigue limits, butting, etc... I'd like to listen.

Slight problem with all of this: anodizing is dyeing a layer of aluminum oxide. Steel spoke can't be anodized, as they have no aluminum oxide, and iron oxide is simply rust. They can have a black oxide coating tho.

And this black oxide coat would be what, exactly?

ALL metals above Silver in the anodic scale have a layer of surface oxide, which can be artificially thickened by making them the ANODE in an electrolytic cell containing an oxidising acid, hence 'anodizing'.

As already mentioned, stainless steel spokes have a tenacious oxide film/chemically adsorbed layer, which can indeed be thickened by electrolysis. RTFT.


If you'd like to wax eloquent about all manner of spoke related things, like: stress relieving, fatigue limits, butting, etc... I'd like to listen.

Really, my speciality is metallurgy within the field of materials engineering. Spokes come under the remit of ferrous metallurgy and materials mechanics, so yeah, anything you want to know, I can at least shed some light on, I hope.

If [Falanx] would like to wax eloquent about all manner of spoke related things, like: stress relieving, fatigue limits, butting, etc... I'd like to listen.
For this sort of stuff, Jobst Brandt's book, The Bicycle Wheel, is very good.

Yep, yep. He and Keith Bontrager are two of the most pensive and knowledgable men in cycling.

The 'soft' method used hydrated chromic acid (C2SO3(aq)) and has almost totally fallen out of favour.

A couple of nitpicks on your chemistry. You forgot the "r" on your formula. Carbon doesn't like to form sulfite salts like metals do ;) . Your formula is incorrect for hydrated chromic acid. What you are looking for is chromium (III) sulfate which has 2 chromium (III) ions and 3 "sulfate" units. Your formula is for carbon sulfite (sorta).


Now, this is the important bit - Alumina (Aluminium oxide... it's great how you can just name the oxide of a metal by knocking off the 'um' and replacing it with 'a', innit?)

One more nitpick, dropping the 'um' and adding an 'a' is only common for aluminum. I've never run across titania or plumbia :D

Cheers for corrections. I wrote that with a duff keyboard and way too little sleep :) It should have read Cr2O3.5H2O(aq)

And yes, Titania, Magnesia, Calcia, Soda(the exception that proves the rule, otherwise known as Natria) etc are commonplace. Just not amongst mountain bikers....

"black spokes break

and black spokes creak"


true or false or somewhere in between?

True but all spokes regardless of color of material can break. After 12 years in a bike shop and 6 inside the industry specing product I can tell you that we never ever considered black spokes to break more often than UCP or nayural stainless. This is a bad question. Once again put yourself in the manufacturers shoes. If you were producing a product that did not reasonably hold up you would soon be out of business.

[snipped] This is a bad question.

Huh??? I, for one, sure learned a lot as a result of that "bad question". Hope you didn't mean it the way it came across.




Once again put yourself in the manufacturers shoes. If you were producing a product that did not reasonably hold up you would soon be out of business.

That's highly dependent on the consumer's definition of the word "reasonably", isn't it? You don't think everyone has the same expectations and desires of a product and is willing to accept the same trade-offs, do you?

Take, for example, the integrated headset design. There are those people who won't buy a bike with that design because once the interface between the headtube and the headset is worn out, the frame is essentially toast. The fact that some people don't support it obviously has not stopped the design from becoming a common feature, and the fact that it's a common feature doesn't mean that it will satisfy everyone.

Capitalism 101: Companies aren't driven by making sure the products they sell "reasonably hold up", they're concerned with squeezing as much profit as possible from those products. It should be pretty intuitive that just because a company hasn't been driven out of business doesn't guarantee that you'll be satisfied with what they sell.

Cheers for corrections. I wrote that with a duff keyboard and way too little sleep :) It should have read Cr2O3.5H2O(aq)

And yes, Titania, Magnesia, Calcia, Soda(the exception that proves the rule, otherwise known as Natria) etc are commonplace. Just not amongst mountain bikers....

Not amongst chemist either, who tend to follow IUPAC nomenclature rules...except when they don't :D You have to be a really, really old chemist to call magnesium hydroxide 'milk of magnesia'. I'm just an old chemist and we very rarely do that...it's more of an engineer thing :eek: :D

Not amongst chemist either, who tend to follow IUPAC nomenclature rules...except when they don't :D You have to be a really, really old chemist to call magnesium hydroxide 'milk of magnesia'. I'm just an old chemist and we very rarely do that...it's more of an engineer thing :eek: :D

I never expected a chemist from your side of the pond to endorse IUPAC :) Whereas I am an engineer, and have to put up with ceramicists, geologists, founders and all manner of non-standard science.

I never expected a chemist from your side of the pond to endorse IUPAC :) Whereas I am an engineer, and have to put up with ceramicists, geologists, founders and all manner of non-standard science.

Piffle! Those are easy. Try working with wood chemists. Those guys speak in Martian!

By the way, we do get something of a good education on this side of the pond. I mean, I've even heard of this new measuring system that uses a base 10 for the units. It'll never catch on here but it looks intriguing :D

black spokes are purty!

Piffle! Those are easy. Try working with wood chemists. Those guys speak in Martian!

By the way, we do get something of a good education on this side of the pond. I mean, I've even heard of this new measuring system that uses a base 10 for the units. It'll never catch on here but it looks intriguing :D


A damn sight better than we get over here any more, with the exception of Cambridge. *Shakes head*

And you can keep your wood chemists. The perverts.