Why am I breaking a ridiculous number of spokes?

Question

First, this is a follow up to this: Why does my back wheel keep becoming untrue?

(The short version is I bought a used bike a few weeks ago, I broke a spoke on the back wheel, replaced the spoke, trued the wheel with a tensiometer, and found that it had become untrue again. The diagnosis was either the wheel was bent, or that the spokes were just settling and re-truing it would sort out the problem.)

I've been riding it over a week with an untrue back wheel (aka Kayak Mode). Today, I checked the wheel because the trouble had become a big issue again, and found I had two (!) broken spokes since replacing the first broken one a week or two ago.

So, why are my spokes snapping like spaghetti? I guess:

1. Because I was riding without truing the wheel
2. Because I'm riding too hard (i.e. coming off curbs)
3. Some combination of the two, or something else.

Thanks!

Your pal, JKD

POSTSCRIPT July 28, 2011

First, thanks everybody.

I wanted to follow up for people who find this question later, and describe the rest of my experience with the wheel.

I kept breaking spokes after replacing them, and by the time I got to the shop again, I had broken five (!) more. They looked at it, I looked at it, and I ended up replacing the wheel. It rides fine now, and as far as I can tell, it was just an old wheel.

Kazah!

Answer 1

Generally, repeated issues with broken spokes indicates either damage to the rim, meaning that the metal hoop of the rim is physically bent while under no tension, or that the spokes are at the end of their fatigue life.

Any wheel has an expected use life, and usually, you will wear a track in the aluminum rim from braking forces before the fatigue life of the stainless steel spoke becomes an issue. However, if the rim is damaged, as referenced in your previous question, then the tension of the wheel cannot be evenly consistent, because some spokes must be tighter than others in order to hold the rim true and straight. If our wheel is unevenly tensioned, it allows a far greater amount of movement of each spoke during the revolution of a wheel, and this stresses the spokes beyond their designed strength. And you break more spokes.

If the rim is not bent, the same issue applies, except it is smaller movement of the spokes over a far greater period of time which has pushed the spoke beyond its useful life.

Answer 2

Several possibilities:

1. The wheel is poorly built -- over tensioned, improperly crossed, wrong side of the flange, etc.
2. You're too heavy for the wheels.
3. You're too hard on the wheels (for the ruggedness of the particular wheels).
4. The spokes are corroded or otherwise reaching end of life.

Riding without truing the wheel doesn't help the situation, but wouldn't by itself cause a problem unless the tension was so far off that a few spokes were bearing the lion's share of the load.

Answer 3

I had the same issue with a set of wheels. I was breaking a spoke every week or two. My advice was that it was a cheaply built wheel with weak spokes. Whenever I replaced a spoke I marked it and I confirmed that it was always the original spokes that were snapping.

I upgraded to a new set of wheels and haven't had any trouble since. I'd suggest having a good hard look at the bike and either buying new wheels or upgrading to a better quality bike. Wheels are a pretty safe investment because you can transfer them to a new (similar) bike relatively simply.

Answer 4

Because I was riding without truing the wheel

This. When the wheel went from true to not true, some spokes lost tension while others gained tension. Otherwise the wheel would have remained true. And uneven spoke tension is the recipe for broken spokes.

That said, jumping curbs is generally not the toughest thing spokes have to endure. That title goes to hard acceleration in first gear, or to braking if you use disk brakes: The torque needs to be transmitted through spokes that are almost at a right angle to the torque forces that they need to transmit, so the spokes experience much greater differential stresses than you might assume if you only looked at the transmitted torque.

A wheel generally becomes untrue when some of its spokes loose all tension during acceleration or braking. This loss of tension allows the nipples to turn erratically, worsening the situation. And once a spoke looses all tension regularly, its head is soon to break off due to fatigue.

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Your spokes may be damaged beyond repair, but in my experience it is of utmost importance that all spokes have very similar tension. This is more important than the wheel being perfectly true. You won't feel a few millimeters sideway wobble, but if truing the wheel forces you to have some spokes with significantly more/less tension than others, the wheel will soon go out-of-true and start breaking spokes.

Answer 5

Spokes usually break from fatigue. Hitting things hard might dent the rim, or cause a spoke that is about to break from fatigue to fail, but it won't in itself fatigue rims.

If your a heavy guy and the wheels are light, that might cause the spokes to fail early.

Otherwise the chances are that the wheel just wasn't built very well. After all most cheap bike never actually go very far, so that fatigue life might not be the most pressing issue for the manufacturer.

Once one spoke in a wheel has broken from fatigue, the rest will follow shortly.

If the rim is not very worn and has no obvious dents, you may be able to get the wheel rebuilt by a good bike shop. Or you could by The Bicycle Wheel book by Jobst Brandt and it yourself.

Answer 6

Just for future reference, I'll add this:

My son purchased a "Eurobike" of sorts a couple of months back and brought it on the week-long group bike tour we took last week. The bike is branded by a purportedly good outfit in California, and built (of course) in China. It is a 26-inch unsuspended hybrid, with a variable-speed NuVinci rear hub and a Shimano generator front hub. In general it appears to be a good quality bike.

Before the ride started it was discovered that one spoke was broken on the rear wheel (and a repair was effected), and during the last day of the ride a second spoke broke. Both spokes broke at the nipple.

On examination of the wheel it could be seen that the large-diameter hub and the 2-cross pattern caused the spokes to approach the rim at an angle substantially off from 90 degrees, causing quite obvious bending of the spoke where it enters the nipple. The tendency to break at this point was likely further abetted by undersized, poor quality spokes.

I am guessing that the wheel will need to be relaced, though we will see what the bike shop and manufacturer say after my son gets back to California. It's vaguely possible that the rim was drilled for the off-angle nipples but the wheel was built wrong, with the odd nipples in the even holes or some such. In any event, heavier gauge, better quality spokes are needed.

(Other than the spoke problem -- and an associated problem with the enclosed chain while servicing -- the bike performed admirably, handling some very substantial hills.)

Answer 7

I have a Giant road bike from the late nineties, which hung unused in the garage for ten years. When I started riding it again seriously a few years ago I snapped quite a few spokes, perhaps a spoke or two a month. The broken spokes were on the drive side of the rear wheel of course; the spokes on that side necessarily have higher tension because of the offset of the hub flanges. The owner of the LBS said that my problem was "cheap Taiwanese spokes". (It was kind of him not to say anything about my being a heavier rider at 210 lbs / 95 kg.) He predicted that eventually I would have replaced all the drive-side spokes (with replacement spokes from his shop naturally) and then I would no longer have the problem, and that's exactly what happened. I wish I'd changed them all at once, instead of one at a time.

So for those with similar problems, it's possible that the manufacturer built the wheels with inferior spokes to save a little bit of money, and that all you need to do is change the spokes.

Answer 8

Are the spokes breaking at the nipple? I had this problem, wheel was rebuilt with too short spokes. Maybe the old hoop was asymmetric and they swapped everything to a symmetric hoop. (Ibis 735 to WTB kom) not sure. I keep replacing the spokes and they keep snapping right down the line(the old, not new), one snapped just sitting there after I just finished. Looking forward to the day I get back to the first one I replaced and hopefully the problem goes away toooooo 😂😂😂😂.