deacon mark

First time ever I had a broken spoke. I built the wheel it is Velocity Aero Head rear with offset center. I built it 2 years ago and have almost 4000 miles on the wheel. It did a 28 hole 3 cross using velocity hubs, 292mm hoshi double butted spokes they 14/15 or close. In the 2 years the wheel has be absolutely true I have never touch them since the build and like them a lot. For the record I am 6''2 and about 177 pounds. The spoke broke at the thread about 3 threads from the hub-end if that makes sense. THere are no signs of stress to the eyelet and the nipple is in perfect shape, and if I can extract the rest of the spoke I can reuse it. I manage to replace it in almost no time and the wheel true back almost instantly and I did a little stress relief for the new spoke. I manage a 18 mile ride and everything is fine.

Here is the funny thing. I last rode the bike exactly two weeks ago on a 60 mile ride and did not notice a thing wrong. I put the bike up in the garage and today when getting it out to ride I notice the brake rubbing and could not not fiigure out what was going on. Then after deciding the wheel was not true I notive the spoke dangling and of course dawn comes. I cannot imagine I would have not notice this if had happen on my 60 mile ride, I assume the spoke snapped while hanging in the garage. Any one had this happen? Nothing would have happen in the garage as the bike was hanging so I am lost. Could it be a bad spoke? I do not ride in the rain and normally easy on my bikes for wear. I did however on the 60 mile ride have wet pavement much of the time but no rain at all. I do not normally even ride when the pavement is wet most of the time, but I just cannot think that would matter. What do the experts think? I think the tension of the wheel is fine pretty even all the way around and get about 100 on the DS based on the park charts.

mrrabbit 

Where did the spoke break again?

Photo?

=8-)

Al1943

I don't understand the threads near the hub. Is this a straight pull hub with threads at the hub?
The 100 kgf is not very high for the drive side. Did you check the tension after pumping the tire up to riding pressure?
Did you assume the smaller diameter part of the double butted spoke when converting deflection numbers to kgf tension?
Are the spokes entering the correct side of the rim?

ultraman6970

The spoke broke at the thread about 3 threads from the hub-end if that makes sense. <-- no, it doesnt make any sense.

Same questions as the other two guys. The spoke broke at the nipple then?

deacon mark

I am sorry the spoke broke at the threads but it was about 3/4 of the way down the tread. It is a standard spoke not a straight pull with threads at the hub. I was just pointing out the spoke broke at the last 3 treads before they run out into the smooth part of the spoke. I do wonder if I should go around and tension the whole wheel higher. My average reading on the park meter is 17 with the using the park meter with out the tire. The reading on the spokes with the tire at 120psi is 16. The spokes are 1.6 in the center and 2.0 at the end. Yes the spokes are on the correct side of the rim it is an offset. Yes the spoke broke at the nipple

Bill Kapaun

Since this is an offset rim, I assume it's a rear instead of a front disc???

IF a rear, which side?
IF DS, 17 (assuming a Park tension meter) is a couple 'notches" too low. You want it around 110KGF vs 80-90 KGF that you have.

Maybe too much spoke flex at the nipple/thread junction??

Edit:
In your initial post, you state they are 14/15 DB spokes.
You later state they are 1.6 in the middle.

That makes a major difference in spoke tension, 1.8MM vs 1.6MM
My tension statement above was assuming 1.6MM IF 1.8MM your tension is much lower.

Al1943

The spoke holes are offset and alternate from side to side. The spokes should enter the holes closest to hub flange holes.

Al1943

Has the chain ever dropped off the cassette and onto the spokes?

deacon mark

I am accurate so I measured the spokes at 1.6. These are hoshi and hard to get the specs I just said 14/15 and then measured to be accurate. I remember when I built the wheel I was surprised they went to 1.6 instead of the usual 1.7 like Wheelsmiths or 1.8 DT. I went around and took a reading of all the drive side spokes and they all fall at 16 to 15 on the park tension meter and the wheel is true laterally and radially. I have the lateral true to less than .3 mm they spin nice. I just wonder if I may need to increase the whole tension of the wheel. I initially thought it could have more tension when I built the wheel but after riding them and no issues I left them alone. Velocity told me to aim for 115 to 130 if I remember correct and then let the non drive side fall as it may.

FBinNY 

I interpret three threads from hub end and the rest of the post to mean that the broken spoke still has three threads attached to the main part, with the rest inside the nipple. That probably means that it broke at the first engaged thread, which is the second most popular place for spokes to break.

The OP should take a look at the other spokes and see if they align well with the nipples because poor alignment is the main cause of thread failures. If the bike is ridden in wet winter conditions, a contributing factor could be salt related corrosion. Water sprays or wicks between the spoke and nipple and when it evaporates it leaves the salt behind to attack the steel. Most stainless steels used for spokes are not marine grade, and even if, they are still vulnerable to the ravages of salt and time.

Since it's only one spoke you might chalk it up to a fluke, replace it and move on. However you might want to hedge your bets by dissolving grease or anti-seize in solvent, applying one drop to each nipple, and spinning the wheel to drive it in.

Breaking during storage is classic for chloride damage to spokes. It's a time, not stress related process, and so spokes can let go at any time. I had a wheel I keep in Cozumel have this problem so bad that after hanging in the garage all summer I came back to find 1/3 or the wheels broken cleanly. It looked more like vandalism then mechanical failure, and I'd have been suspicious except that the remaing spoke were about as brittle as dried spaghetti.