mushyman

Hello All,

So, over the years, three spokes have broken from my rear wheel at different times. I am planning on replacing the most recent broken spoke. What do we think this keeps happening? Maybe I need to tightening all the spokes a little more evenly? I do not believe I need a new wheel.

RCMoeur 

It's my understanding spoke breakage (especially at the bend) is not from excessive tension but fatigue from repeated stress reversal; e.g. a spoke that loses tension and then regains it every revolution, much like repeatedly bending back and forth a wire. You can try gradually increasing tension on all spokes in a wheel (after replacing the broken one and truing), but if you're not experienced in wheel building or maintenance there is a slight chance you can make matters worse by uneven tension, rounding off nipples, etc.

Some people would suggest taking the wheel to a bike shop for evaluation or repair. If so, try to take it to a shop which has a reputation for good wheel work, as unfortunately I've observed many shop staff nowadays may not have a broad enough experience base to deal with such a problem - and they may just try to sell you a replacement wheel from what they have in stock. But at current shop rates, a replacement wheel may or may not be less costly than mechanic time.

Bill Kapaun

How old?
What side?
Broken J bend or "other"?
Time/miles between breaks?
Stored near chlorine? Tiny black specks/inclusions.

As a general rule, the 3rd broken spoke is considered a trend and time to respoke.

mushyman

Thank you for your response! I am going to try and do this myself. I would love to learn. Alright so, I am going to need a new properly sized spoke, put it in, tighten it, then true the wheel. Are those the basic steps that I need to do to get this bike up and running?

mushyman

Thank you for the response, Bill. The bike is from the early 2000s. It is on the drive side. I don't know what j bend is, so I can't answer that question. The breaks occurred a few years and many miles apart.

maddog34

to slightly restate Bill's Questions...

How old is the wheel with the broken spoke?
About how many miles has the wheel been ridden?
What side is the broken spoke on?
Have all the broken spokes been on one side of the wheel?
Did the spoke break at the hub/J bend or somewhere else?
What is the approximate timespan between the three broken spokes?

proper advice will be only a guess without the answers to these important questions.

Bill Kapaun

J bend is the part that attaches to the hub.

Andrew R Stewart 

We joke about the death spiral of a wheel at work. The first circle around the spiral is the biggest, for this story say 7k miles, before a spoke brakes. Next time around the spiral to the second spoke breakage might be only 4K more miles. repair the cycle starts again bit now a mere 2K miles went by. With each spoke replacement/repair the period to the next shortens. After the second or third spoke is replaced many will start to question the wheel's reliability and the cost of down time during the season.

One method to help reduce the next spoke breakage being any sooner than it might be is to fully detension the wheel/spokes during the broken one's replacement. This will provide the service guy more understanding of the rim's natural straightness (with no spokes pulling this or that way) and how it might effect the long tern reliability as well as making repaired wheel's spokes more likely to be consistent in their tensions WRT to each other. But this takes more time and during the season few shops have the luxury of this level of work. Andy

FBinNY 

It's hard to assign a specific reason for spoke breakage because there are too many variables. Both overly tight, and overly loose tensions can cause premature failure.

However, absent a specific immediate cause, like a crash or large pothole, spokes fail from metal fatigue over time.

The process is like making popcorn. First an outlier will break long before any others. Later another outlier, then the next and so on in ever shorter time frames until it seems like they're all going in rapid succession.

So the key is figuring where in that process you are. After the 2nd or 3rd spoke, I get very conscious of the interval, knowing it'll only get shorter, never longer.

So, how long has it been, and what are you willing to accept?

cyccommute 

While your analysis is partly correct, it’s not complete. Every wheel undergoes tension/detension cycles no matter what how high or low the spoke tension is. Increasing the tension of the spokes doesn’t keep the rim from deforming at the contact patch. Because the rim is only under tension and not solidly connected to the rim, there is nothing to resist compression of the rim. Some rims aren’t going to be compressed as much as others due to the weight of the rider so the spokes may not be as prone to breakage as others. A heavy rider and/or a heavy load puts more stress on the spokes and makes them more prone to breakage because of this flex.

To be clear, I’m not saying that tension isn’t important but just running the tension up isn’t the solution to all spoke breakage problems.

That is certainly becoming more true all the time. Few people want to learn the skills to build or even repair wheels. They are cheap and, if you are only building something that you can buy, there is little reason to build. For a wheel that has multiple spoke breakages, there is probably little reason to keep repairing it.

I agree that you probably need a new wheel. You can probably get more miles out of the wheel but you are going to keep on breaking spokes.

Your problem could be related to a number of factors. Tension is one of them. Poor build could be another. Poor quality spokes could be another. Load on the bike is also something to consider. I’m a big guy who carries heavy loads and have broken my fair share of spokes. You should probably give us a bit more information about spoke count and whether you are a large rider carrying heavy loads or a light rider on a light bike.

I build my own wheels and have for years. I build with heavier spokes so that I don’t break spokes. Although I reached the conclusions in this article several years before it was written, the article describes how using triple butted spokes results in stronger more durable wheels. The rub, however, is just what RCMoeur talks about above. There aren’t many people who still build wheels. I taught myself to build wheels using a series of article written by Eric Hjertberg, founder of Wheelsmith. He has posted them here. It’s dated with regards to components but it is still a good series on how to build wheels.

FBinNY 

IME the single biggest consideration is riding style.

As noted, spokes undergo tension cycles as the loaded wheel turns, regardless of tension. The tension changes depend greatly on rim stiffness, with stiffer rims narrowing the degree of detention on the bottom, compared to less stiff rims. But the tension increases are always fairly small regardless of the rim.

As long as tensions are such that spoke tension changes stay within the working range, spokes can last almost forever.

All the above applies only to when the loads are radial. It's a different world when they're not, because there's no cap for tension changes due to sideboards.

Riders who tend to horse the bike, especially when climbing or sprinting tend to be harder on wheels, especially if those riders are heavier.

Over the years I've known very heavy riders who never have wheel issues, and light riders who do, including a ballerina who was absolute murder on her wheels.

Paul_P

Can spokes eventually fail where they cross other spokes ?
Not sure if it's a dent or abrasion, but if you squeeze two spokes that cross you can feel them popping in and out of the contact area.
I'd prefer my spokes to remain smooth...

FBinNY 

Spokes get notched there because they move over each other with flex.

ALL my wheels eventually get notched there, which I'm happy for because it means they lasted long enough to do so.

OTOH, while you can wear in a small notch in a few thousand miles, it would take eons to wear them deep enough to be a weak spot.

Bike Gremlin

This.

I would add:
If a wheel has been built properly (with an optimal and even-enough spoke tension), then one spoke breaking could mean it was just a faulty spoke. However, the probability of three or more spokes breaking on a single wheel is very low and usually means something is not good enough. It could be low or uneven tension.

Low tension could be the result of a weak rim. Even with a well-built wheel, the rim could be not strong enough for the rider+luggage weight, for example, not allowing for high-enough spoke tension to handle it.
Uneven tension could be the result of a bent rim, that needs the highly uneven tension in order to stay true.

That's when it comes to fatigue breaking. We should also consider spoke physical damage. A lot of rust or physical spoke damage (such as chain dropping between the cassette and the sprockets) could also cause several spokes to break even though the wheel is strong enough and well-built. When that is the case, it makes sense to replace the damaged spokes, without worrying about the other spokes being problematic.

As you said, to figure out if the wheel was built properly and figure out the most probable spoke breakage cause does take time. It's not something I'd expect a bike shop to do, especially during the cycling season.

Relja

fishboat

Inexpensive and will tell you everything you need to know to spec the spoke size, install it, and maintain your wheels.

https://www.wheelpro.co.uk/wheelbuilding/book.php

cyccommute 

That’s part of the issue, although a relatively small part. The tires absorb a lot of the punishment on wheels. The rim can be damaged by running the pressure too low and bottoming out the rim on a sharp corner but that doesn’t really cause any damage to the spoke.

Much is made of the stiffness of rims but the difference in rim stiffness in most cases is relatively small. Modern double walled aluminum rims don’t differ in stiffness from one model to another all that much. They all have similar wall thicknesses. There are some geometrical differences but one geometry isn’t many times stiffer than another geometry.

Unless you make every corner a square corner, every wheel is going to be subjected to lateral loads just as every wheel is subjected to vertical loads. It can’t be avoided.

cyccommute 

While I agree that spoke breakage is because of faulty spokes, I probably don’t agree with what you consider “faulty”. Imperfections in the spoke material are relatively uncommon. The metallurgy used for making the spokes is generally better than it was 20 to 30 years ago. The “faulty” part comes from poor selection of spoke size. It’s a bit counterintuitive but the most commonly used single gauge spokes are weaker than double butted which are weaker than triple butted. Double butting of the spoke increase strength by 20% over a straight spoke. Triple butting increase the strength another 20% for a total strength gain of 40% over straight spokes. The “fault” is in using the weakest (and cheapest) spokes.

Multiple spoke breakages aren’t uncommon on OEM wheels because the spokes are even more of an afterthought on those wheels than spokes on custom built wheels are. Most everyone picks are hub, picks a “strong” rim, and then says to use “whatever” spokes. Almost zero thought is given to the actual spoke even though spokes are the problem. Seldom does a rim break. Even more seldom does a hub break. Spoke breakage is far more common, yet everyone seems to want to solve the problem by addressing everything but the spoke.

With respect, name a “weak” rim. Or describe what you mean by a “weak rim”. The bike below has a front wheel that has a Mavic XC717 (395g) and a rear wheel that is Velocity Aeroheat (422g). Both wheels are used in rugged conditions with a touring load (43 lbs gear load, 29 lb bike load and my girth which is north of 220 lb) like seen in the picture. I’ve even ridden several miles of railroad ties with a similar load on them. I can’t think of a set of wheels that I own that has seen more abuse. I have had zero issues with the rims even though they are light weight rims. I’ve been running similar weight rims on my mountain bikes for decades. I used to break a lot of spokes but that was before I started using triple butted…i.e. stronger spoke…about 25 years ago. Since then, spoke breakage on wheels with triple butted spokes doesn’t happen.




While that can be an issue, it is a different problem that should be addressed differently. Spoke breakage, especially for large riders on OEM wheels, is a systemic problem that needs a different solution.

Bike Gremlin

All good points.
Still, it is possible for a factory to make a faulty spoke. Which is why I have most faith in the old, tried and tested spokes.
Note: in Serbia, the only available spokes are cheap, "Chinese" ones, so any "imperfection" in wheel building gets punished pretty quickly - but I've seen a faulty spoke or two (or nipple for that matter) from Sapim and DT Swiss too. A lot less frequently, but it happens.

As for the wear rims - one example is a 36-spoke rim that could not stand spoke tensions of ~ 80 kgf. Working with what's available, Chinese straight-gauge 2mm spokes, this just wasn't good enough for a strong heavy rider. As I couldn't source any swagged spokes (or 1.8 mm ones), I had to get a stronger rim (for under $10).

Relja

veganbikes

I would just replace the wheel, you will be chasing spokes all over it for the rest of its life. Unless it is a super high value wheel just get a new one. If it is a super high value wheel then de-spoke it and get it rebuilt by a wheel builder who knows what they are doing.

FBinNY 

I understand that we all have differences of opinion. Also that you seem to have a need to argue about any and every thing. However, selectively parsing posts to isolate items out of context to make posts seem to say what they don't, and create strawmen is poor form.

So, following my rule of not arguing with strawmen, I won't address your points individually. However I stand by EVERY point I made in the quoted post, and remind readers to read it in it's entirety, then draw their own conclusions.

grumpus

I've seen spokes worn where they cross, this is probably because overall tension is low (or the bike has been heavily loaded) so there's some movement and they're fretting against each other. I suspect an accumulation of fine road grit could play a part in the process. If they start breaking there then it's time for a full set of spokes, or a new wheel.

sweeks

I've built several wheels over several years using this manual, and though I'm not a professional bike mechanic, I have had very satisfactory results.

Broctoon

That looks like a good reference, but you don't even need that much. I've been building a few wheels and truing or repairing a few others, with good results. I just study everything at Sheldon Brown's Wheel Building Page.

Bike Gremlin

Having read both sources, I can not recommend the book enough. It's beautifully written, with clear explanations and drawing. The best source I could find to learn how to build (and repair) wheels.

Jobst Brandt's The Bicycle Wheel is great to understand why wheels are laced and built the way they are, while Roger Musson's Wheelbuilding book is great to learn how to do it most easily.

Relja Bookworm Novović

Bill Kapaun

I learned from Sheldon because I had a computer at home and I felt the library would frown on attempting to build a wheel there.
My first 2 wheels both had the 2nd set started wrong and I had to redo. One of the rims had the "less conventional" key spoke in the 2nd hole to add to my confusion.
On my 3rd wheel, the proverbial "light bulb" went off when I realized the spoke holes on the opposite hub flanges were offset! I have to install the 2nd set in the same direction on both hub and rim.