Wheel disintegrating!
 

I've run this stock wheel from the REI Randonee for 13,000 miles so far and had NO trouble with it. Nothing. Nada. It never even needed to be trued - it was perfectly straight. Until yesterday.

So I was riding along when I heard the dreaded POP! A spoke was flopping around. We were about 20 km from town at that point, so I pushed on. About 3 km later - POP! Another one.

We pulled off to set up camp and fixed it - turned out the spokes were fine, but the nipples had busted. As John was truing the wheel, another nipple self-destructed in the tool.

So this morning, we woke up and found.... THREE MORE BUSTED SPOKE NIPPLES!!! We couldn't believe it. I hitched a ride into the nearest town and another one was gone by the time I got here.

I have found a local mechanic who is replacing all the spoke nipples now and I'm hoping to be back on the road by tomorrow.

But - is this normal? Every one of the nipples completely fell apart when he took the wheel apart. Is 13,000 miles about what one would expect from aluminum nipples? I guess when aluminum fails, it fails all at once!

are you sure they were alumiinum nipples? (For the record, it sounds like it) This is probably the worst place to skimp on durability when building a wheel, so I am surprised if the wheel was stocked like that!!!. Brass should certainly last longer... it is sure strange that they all fell apart at once though!

Absolutely they are aluminum. The guy is putting steel onright now. We had never, ever had a spoke nipple fail before, so didn't think to check!

you sure are a great tester of wheels! I wonder why you've got aluminum nipples though.

It's not uncommon for a spoke to break and put the wheel out of true which put more stress on other spokes. You can continue that for a bit and you'll see how one spoke can become 6. This only really causes trouble when you have, like in your case, weakened nipples, or weakened spokes.

Lee - I'm riding the REI Randonee and it came with aluminum nipples. We didn't even think to check since we've never had nipples fail at all. Next time, we'll have them swapped out for steel or brass!

emperor - I can see how one broken spoke leads to others, but the fact that they broke in such quick succession - two within 3 km seems odd. And then, after we fixed those ones, another three broke during the night when the bike was just sitting htere! And other one snapped while I was hitching a ride in the back of a truck. Odd that they would all give out like that.

Watch for galvanic corrosion (happens between alu. and steel) around the rim/nipple interface. not a huge deal, but some drops of oil can help prevent it... more of a problem where there is rain/salt on roads.

the rim looks great! We don't see any signs of corrosion on the rim at all. Good thing as there is no way I could replace it here!

It sounds to me like the aluminum nipples were simply the weak link on the whole wheel. Aluminum is fine until you overstress it. That's why torque values are so critical when working with aluminum. When the first nipple failed, it overstressed the others like a set of dominos falling. The steel nipples should last long time.

that's what we're hoping!

That sounds like the most plausible explanation. All the nipples are the same dimensions, they all get wet at the same time, the corrosion progresses at the same rate for each nipple.

my experience with galvanic corrosion and aluminum nipples (sample of 1) is that they just get stuck and it's time for new spokes and nipples. On my wheel, every spoke was stuck and you couldn't turn them. Since some of the nipples on the wheel in the OP fell apart, it sounds like they were cracking. Maybe a batch escaped heat treatment or were damaged by the wheel building machine. I always build with brass nipples now, the small amount of weight saved with aluminum doesn't make sense to me.

You got 13,000 miles out of a machine built wheel and you're complaining?

Exactly! That's a lot of miles for a wheel. You did extremely well. You should be happy. As mentioned before, one spoke breaks, then the others that are ready to break get stressed more. Nothing odd about that, it's normal.

When one spoked popped you kept riding? Did you stop and check the wheel or at least secure the spoke from flying around and getting caught in something? If you did not, you are lucky nothing else happened.

Hi,

nipples - who cares... on the Icefield I lost 4 side by side. I just proceed until the next dealer (spokes were fine - nipples broke by external force) appr. 100 km - no problem with the rim

My problems are rims. I would be happy if 50% of the my crashed ones had last 5000 km.

Thomas

FWIW, that's seizing due to galling. With galvanic corrosion, the softer (less noble) metal disintegrates.

No matter though, it all stinks when it happens.

I don't think Nancy was complaining... just trying to work out what caused the spoke fail... and at the same time sharing her experience so that others may avoid the same problems. Thanks Nancy! :)

I think you just hit the fatigue life of the aluminum nipples. Unlike steel, aluminum can reach its fatigue life from the accumulation of small repeated stresses. When the fatigue life is reached there is a sudden failure of the material.

Wikipedia explains it this way: "One important structural limitation of aluminium alloys is their fatigue strength. Unlike steels, aluminium alloys have no well-defined fatigue limit, meaning that fatigue failure will eventually occur under even very small cyclic loadings. This implies that engineers must assess these loads and design for a fixed life rather than an infinite life."

There have been some pretty dramatic instances of aluminum fatigue failures. Although not the only cause, aluminum fatigue failure contributed to incident in 1988 when the roof of an Aloha Airlines 737 peeled off in mid-flight, sucking a flight attendant out.

Your instance is a bit less dramatic, but it seems like the same thing. Brass alloy nipples should hold up better or at least not all fail at once.