Why am I breaking a ridiculous number of spokes? 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:


Because I was riding without truing the wheel
Because I'm riding too hard (i.e. coming off curbs)
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!
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.