alcjphil

In the first post you said "I have a cyclocross bike that was repurposed by MEC (mec.ca) as a touring bike." That does not sound as if they sold you a touring bike but that they made some unknown changes to make it useful as a touring bike. I am a MEC member. Go back to them. Explain the problems you have had. Be totally honest about how you have used the bike and about the spoke breakages. You probably bought the wrong bike for the usage you put it to. Cyclocross bikes sound so much more exciting and fun than touring bikes, but they are not the same. A good touring bike can be a competent cyclocross bike, but a competitive cyclocross bike is not ever going to be a good touring bike no matter what rack fittings it has

BeeRich

Yes. It's from 2012. I did not buy the wrong bike for my purpose. It was sold as a touring bike as I am a bike tourist. They did not get any requests from me to change any bike and they didn't change any bike. The Cote was sold as a touring bike which is why I bought it. It was not sold as a cyclocross touring bike, regardless of how great they sound to you. I didn't know what cyclocross was at the time and I had to look it up and see other events to know what they were. At no point did MEC tell me anything about cyclocross.

They will not do anything to a 7 year old bike. I've been an MEC member for over 35 years. Your assumptions and insistence are misplaced in this thread. I can afford new spokes. I'm more curious about what could be happening and how I could EASILY fix it, as opposed to learning yet another hobby, especially on something that's notoriously time-consuming and difficult.

79pmooney

Spokes that are too short break just like the one in his photo. Properly tensioned or not. But whether the breakage is from too short or not enough tension, the only good solution is to cut out all the spokes and rebuild the wheel with proper length spokes (and double butted of appropriate gauges). In the final build, the new spokes should be very close to the top of the nipples. Easy to see from the tire side of the rim. Ideally you cannot get a screwdriver onto the nipple slot. Sticking out past the nipples is perfectly OK as long as - the spoke ends don't reach the innertube and there is still thread to go before binding. If the innertube is an issue, the spokes can be filed shorter.

If the OP chooses to rebuild with the same spoke crossing pattern. then he can simple take one existing spoke (before any spoke cutting) and measure the distance from the spoke end to the top of the nipple. Add this to the current spoke length. If this is a rear wheel, do this on both sides. Again, if this is a rear wheel, use spokes one gauge heavier for the right, drive-side spokes.

Doing any less than the above is choosing to stay in your little spoke h***. If wheelbuilding isn't in your future, find a good wheelbuilder. Do this before you tour again.

Ben

alcjphil

"I have a cyclocross bike that was repurposed by MEC (mec.ca) as a touring bike. " From your original post. Yes, you bought the wrong bike unless MEC modified your bike for the type of touring you do. "Touring bikes" run the gamut from light to heavy. Looking at your pictures, you needed a full on touring bike, not a cyclocross bike to be used for touring. I am not saying that you should expect that MEC should reimburse you, nothing like that. All I am saying is that you should ask for their help to find reliable wheels for your bike. There is no easy fix for frequent broken spokes, you cannot do this without knowing why it happens

BeeRich

That's what I was thinking. But since it's a 32 spoke set, I might just start fresh if I decide to go down this road. I hear you on the "adding new spoke length" in the current system, but I should turn this into a project. MEC currently sells 32-spoke configs as touring setups.

blakcloud

Cycommute gave the most plausible answer to why your spokes are breaking and this was echoed by others. If you rebuild with the correct spokes you still have the issue of 32 spoke wheels which aren’t ideal for loaded touring. It can be done but you run the risk of a different kind of spoke failure. Best solution, 36 spoke wheels. Second best, having a pro wheel builder rebuild. A loaded touring bike is not the best to experiment with your first build. If you are confident in your abilities then go for it. Having a truing stand, tension meter and spoke prep would certainly help. Good luck.

BeeRich

OK maybe this is confusing. MEC sold it as a touring bike. That's it. I bought the bike sold as a touring bike. MEC doesn't know me from Jack. Touring means touring. There are no levels of touring. Going to the Mac's Milk is not touring. If I want reliable wheels, obviously I wouldn't be going to MEC for guidance. They sold me this touring bike with non-touring wheels, according to this thread. I'd rather just bite the bullet and either find a reputable source for proper touring wheels, or find someone to help me build my own.

BeeRich

A proper new set seems best. I'm now thinking about people I know in Toronto. There's a guy I met that builds wheels and that's his specialty. I met him down the street and they know me as a cycle tourist. I just have to find the guy. I'm sure someone in this town can help out.

WizardOfBoz

You can kind of check length. If you remove the tire and rim strip, you should be able to inspect where the tips of the spokes are wrt the distal surface of the spoke. If you can stick a paperclip into the threaded spoke hole 4-5 threads or so (about 2.5 mm), then you have a problem. A single mm or so is better.

Also, your spokes appear to be straight gauge. This puts a lot of stress on the spokes at the threads, and at the j-bend. Butted spokes, with sufficient tension, should do better.

ThermionicScott 

The spoke breakages have nothing to do with your disc brakes, and everything to do with the short spokes Stewart pointed out, that's for sure. Good that you're thinking about this before setting off on your next tour.

BeeRich

OK, just to be clear, the spoke broke outside of the nipple, as per suggested by your image.

EDIT: From the looks of it, there ARE some threads on there. I guess I haven't had a good look at the breakage. This picture was taken in May of 2012. I should do a complete inspection.

BeeRich

Can you elaborate on those two points? Here's my thinking so far:

- Stopping force comes from the disc, which is attached to the hub. That translates to tension along the spokes, which pull on the nipples and the rim eventually. Rim brakes slow down the rotation of the bike on the rim, and the hub follows suit. The spokes just get a passive role in that situation as they roll freely outside of the restriction on the rim where the pressure is applied.

- Short or long insertion into nipple threads ultimately results in the same tension (mentioned above) in either 50% of the threads taking that pulling force, or 100%. Reducing the number of threads would put emphasis on the threads both on the spoke and nipple. How does this translate into breaking at the first location outside the nipple? If anything, it shows the whole threading in the nipple and spoke remained intact, but the clean spoke on its own, had the flaw. Weakest link, as I see it.

Like I said before, I'm ultimately interested in how all this works and how to get around it. These are 1.8mm continuous and it's been suggested I get 2.0mm but double or triple butted. Reducing the shaft portion seems counter-intuitive.

ThermionicScott 

You're correct that discs "push" and "pull" on the spokes in a way that rim brakes don't, but so do drum brakes. And rear wheels have done this since day one, due to drive torque. So thanks to 100+ years of experience, this is a non-issue for well-built wheels.

The theory behind double-butted spokes is that threading the end makes it weaker, and forming the elbow on the other end also reduces its strength there. So making the mid-section thinner helps keep any one part from being a weak link. The thinner mid-section is also stretchier, so it can elongate with increased tension or shorten with decreased tension, taking the stress off the elbow or threaded end.

BeeRich

Ah good point about drum brakes and driving forces. When I brake using my current touring system, hard braking makes me cringe, knowing these forces are at work.

OK it sounds like I need to read up on all this. This is how it all starts. Heh. Thanks for the notes.

CliffordK

I'll grant you that broken nipple heads are a sign of short spokes, but I am not seeing a lot of evidence that was the problem.

At this point, remove the tire, tube, and rim tape and look at where the spoke ends are. Bottom of the slot is probably OK. Top of the slot is ideal.

Estimate how much short or long the spokes are, and then measure the spokes to get ideal length (two lengths on the rear).

It appears to me as if there is a slight outward bend of the spokes at the nipples. That puts a lot of stress at that joint.

The spoke holes in the rim appear staggered, with the holes closest to the right side of the wheel going to the right flange.
And, the holes to the left going to the left flange.

Those sockets may be difficult to deal with, but I've heard of taking a drill and gently reaming the holes to the correct angle.

BeeRich

That's a good point. Rear is where the breaks happen, as few as there might have been. The difference in angle on the approach to the nipple, could be the issue. I can only assume there's no asymmetric nature to the seat that the nipple sits in. Maybe the staggering affords the angle of which you speak. I guess an email to the manufacturer might help.

WizardOfBoz

Ok, clearly not breaking at the nipple neck which is what the picture I posted would imply (an important consideration, but not your problem - sorry). If the spokes are breaking somewhere in the threaded section there's a couple of explanations. I will stand behind the suggestion that straight-gauge, unbutted spokes put a lot of stress on the j-bend and threaded section. And spoke tension too low could be causing the dreaded loss of tension which plays hell with the spoke life. One other possibility. If your spokes were improperly threaded, this could leave too small of a minor diameter. Or if the threads were cut and not rolled they'd be weaker and possibly undersized.

For now (as others suggest above) replace one or two spokes and true the wheel. Pretension (squeeze each pair of spokes a bit) and retrue. Then pluck all of the spokes. They should have about the same tone/same tension. You can do this on the road.

Off the road, I'd say that you could check spoke tension but since you're already breaking spokes they're probably fatigued (as suggested above) and so replacing a few spokes and retensioning may be what military folks call "reinforcing failure". They try not to do that, I'm told. Either re-spoke that wheel with butted spokes (check hub bearings and rim roundness and flatness first - you don't want to try to lace up a rim that's kaput), or get a different wheelset (or rear wheel if that's the only place your breaking spokes). If you respoke, have a shop do it, or read up a lot and measure your hubs and rims and such to ensure that you get proper spoke length.

Its a nice looking bike, and I can tell from your note you enjoy riding it. Good luck.

WizardOfBoz

Some rear rims are asymmetric to at least partially reduce the need to dish spokes so extremely. Some rims are drilled and have eyelets that allow for the angle the spoke enters the rim. So the straight spoke and nipple are aligned with the rim hole with no bending. If the holes are not angled, there's a step in wheelbuilding where the spoke is bent ever so slightly near the nipple to allow the nipple to leave the rim at closer to a 90° angle. Jobst Brandt shows this The image below is from my copy of the book. The book is copyrighted, used here claiming fair use. Strongly recommended if you have any interested in wheels or wheelbuilding.

If you have your spokes replaced (with butted spokes!) this is a step that your wheelbuilder should do.

BeeRich

Ya it's a super bike, but knowing I'd have a proper wheelset done for touring, would be a major part of the tank feeling comfortable. I hit some major crap on the road as you could assume. My rear aluminum rack broke arriving in my final destination of Amsterdam, out of pure flex during my E12 Tour of Europe. Handy, that it suggested that aluminum isn't the best material for holding three bags.

Where I stand now is a new set. Either find someone who could show me how to do it, or buy them. A major aspect of all of this is learning stuff like this. I've been fixing/tinkering for decades.

For the thread: I see butted spokes not as a thinner shaft but an enlarged threaded tip/shoulder, since that's where the challenges seems to be.

BeeRich

The problem is that I do have an interest, but little time. Heh. Such is always the case. Better than the opposite.

It's interesting that the spoke hole (rim-spoke shoulder) and the nipple armpit (?) aren't really designed for a pivot on that downward tension. Much like how train wheels are not flat with respect to rails, the train bases its steering on its ability to rock along its camber. This sort of mechanism could encapsulate non-symmetrical tension in both transverse and longitudinal axes, taking into consideration rear hub and cog-set displacements, as well as various crossover threading patterns.

Nothing like a great set of nipples. Heh. Wrong forum.

WizardOfBoz

BeeRich, yeah, I've been a bikey for a long time but I'm building my first set of wheels (actually rebuilding and old set).

Your "larger shoulder" point is often missed by the weight-wienies who count grams. A thinner center section actually flexes more (it has a lower "spring rate") than a thick section. This flex puts less stress on the larger j-bend and threaded section. It also means that, if properly prestressed, the spoke can stand a larger deflection without going slack.

Where did your rack break? I don't think you can write off aluminum - most racks are Al. But if the rack design has poor design, including mounting points that are inadequate*, aluminum will fail. But so will steel, titanium, etc.!

Your European tour sounds like it was a lot of fun. Good riding.

*Or, ahem, if they are overloaded. Just sayin'.

BeeRich

So a wheel works by the compression from hub down to the rim on the ground, or the rim holding its shape and providing a hanging section from the top arch, down through the spokes to the hub? Or a combination of both tension and compression?

I was originally thinking a mis-tuned set of spokes would have a semi-loose hub which would have a rotational frequency of tension-loose which is a problem for metals. Coupled with hard braking, heavy bags and terrain issues, I'm not surprised spokes broke. But then again, my city hybrid which I beat the living snot out of, never has had these issues. I should study those wheels a little bit as well. He has no suspension. 1992 Ironhorse MT700R when that company made serious bikes. It's a shame they went mainstream.

As for my last touring rack, there was some kind of extra arm on the disc-brake side that came off. The flex on the resulting rack increased a lot, but I had two days left with bags, all in Amsterdam and Schiphol.

I replaced it with a Tubus stainless rack, which is more solid than my dating experiences. I have some notes for a write-up that I haven't published yet, about the weights of my bike, bags, distribution, etc. Seems legit, but then again, what do I know.

I'm including some interesting pics.

ThermionicScott 

Neither analogy ("stands on bottom spokes" or "hangs from top spokes") is completely accurate unless spokes are completely losing tension, which is why so many flame-wars have been fought over it. A good wheel performs as a unit. I highly recommend Jobst Brandt's "The Bicycle Wheel" (electronic copies can be found online, and since the author and publisher are both no more, I wouldn't feel super-guilty about seeking that out.)

Anyways, I think the solution to your problem is still simple: 1.8mm center sections are probably wise for your touring loads, so you just need to beef up the ends and make sure they're long enough. 2.0/1.8/2.0 spokes are easy to find (DT Competition), and spokes with even beefier elbows are available. Have your wheelbuilder redo the wheels with proper spokes, stress-relieve the bejeezus out of them, and they should hold up a lot better.

BeeRich

If I change the setup (I think I had 3 broken spokes), then I'll go with a new setup with 2.0mm and 36 spokes, butted.

WizardOfBoz

I agree with ThermionicScott's suggestion of 2.0/1.8/2.0. I'm rebuilding by Superior with 2.0/1.65/2.0 for front and rear non-drive side, and 2.0/1.8/2.0 drive side. Using the 1.65 (14 gauge) mostly because that was the original size. But for a touring bike, with luggage, the 1.8 will be better.

Also, his point about how spokes support the bike was better than I could have explained it. Jobst Brandt did discuss this in his book.