Bicycle Mechanics - broken spoke--how dangerous?

I have a pair of Real Design Ultrasonic wheels with about 1000 miles on them. Without warning one of the front spokes broke. Fortunately, I was going slowly and stopped without incident but the wheel warped rather markedly and lodged against the brake pad. The wheel has 20 bladed straight pull spokes. My LBS fixed the wheel, and said they could not find any particular reason. The manufacturer, via e-mail, also felt this was just a fluke. My concern is that given the rather marked and sudden deviation of the wheel that the consequences could have been ugly had I been descending at 45mph. Am I legitimately worried or should I just ride and forget it? The wheel can be viewed at the manufacturer's site (http://www.real-design.com/2005/ultrasonic.aspx).

Holds trueness better than conventional rims because of reinforced carbon hoop

Low spoke count wheels, by nature, have rather undesirable failure characteristics. The spokes are usually under quite a bit of tension, and when one lets loose there aren't any that are close to take up the load. Combine that with what sounds like shoddy build quality and you've got yourself an exciting pair of wheels. That line above, taken from their website, is a total crock.

It happened to me last October at 40 mph. I was lucky it was the rear wheel but it acted like a giant brake and even chew up a bit in the seatstay carbon.

I'll stick with 32 spokes per wheel!

I've broken a spoke on my rear Ksyrium and the wheel stayed perfectly true and round. I actually ended up putting an extra 500 or so miles on it while waiting for replacement spokes. After putting the new spoke into place, all I did was tension it. No truing was necessary.

Some low-spoke count wheels are simply that... low spoke count. Other manufacturers overbuild the rim and make them very stiff so they can suffer a spoke failure without warping.

Spokes fail for a variety of reasons. There is nothing you can do to guarantee an indestructable wheel.

I haven't seen any studies on this, but I wouldn't be surprised if uneven spoke tension turned out to be the greatest cause of spoke failure.

To reduce the odds of spoke failure make sure that all your spokes are evenly tensioned ( + - 10%), for a front wheel. For a back wheel that rule applies separately for drive-side spokes and non-drive-side spokes. (Drive-side spokes are at a greater tension than non-drive side).

Lastly, don't think you can "set it and forget it". You need to continue to routinely check your wheels for rim cracks, trueness, loose spokes, uneven tension, rim wear, etc. Wheels are subject to lots of stresses and need to be inspected regularly.

Bob

That's one of the reasons I'm not a fan of manufactured wheels. Wire spoke wheels are a proven, albeit old school, technology. There is nothing like a wire spoked wheel built by a competent wheel builder. ;)

That's one of the reasons I'm not a fan of manufactured wheels. Wire spoke wheels are a proven, albeit old school, technology. There is nothing like a wire spoked wheel built by a competent wheel builder. ;)

And factory wheels use bubble-gum for spokes? I think the most important thing you can do to ensure good spoke and wheel life is to make sure they are properly tensioned and stress-relieved. Even if you get factory-made wheels, you should get them checked and prepped prior to installing them.

And factory wheels use bubble-gum for spokes? I think the most important thing you can do to ensure good spoke and wheel life is to make sure they are properly tensioned and stress-relieved. Even if you get factory-made wheels, you should get them checked and prepped prior to installing them.

I think she's just emphasizing that there's no comparison to having complete control over every aspect of the build.

I've broken a spoke on my rear Ksyrium and the wheel stayed perfectly true and round. I actually ended up putting an extra 500 or so miles on it while waiting for replacement spokes. After putting the new spoke into place, all I did was tension it. No truing was necessary.

Some low-spoke count wheels are simply that... low spoke count. Other manufacturers overbuild the rim and make them very stiff so they can suffer a spoke failure without warping.

Wow! You must be a feather weight and had ridden the 500miles at about 10mph...or had a very good low deductible insurance policy! Once you break a spoke on a non-conventional wheel (low spoke count, radial and/or assymetric lacing pattern) you need to carefully ride home and fix the wheel before you ride it again. The Rims usually are usually sturdier but prolonged riding can stress and fracture the wheel especially Aluminum and carbon materials. No matter what you think nor how incredibly luckey you seem to be the wheels are a system and are designed for minimal stressing in the way you did on your wheel. Keep your eye (with a magnifying glass) on the area around the erstwhile absent spoke region and toss the wheel at the first sign of cracking or you might need that insurance policy. Catastrophic failure ain't pretty. Good Luck.

Wow! You must be a feather weight and had ridden the 500miles at about 10mph.

I'm not incredibly light (145lbs) and I didn't exactly keep my speed down. 200 miles of that 500 was on the STP actually. I had noticed the broken spoke right before the weekend. Admittedly, the spoke didn't completely snap. It was bent near the nipple and the nipple was cracked.

http://www.neebu.net/~khuon/albums/mavic-ksyrium-tools/PICT0007_001.thumb.jpg (http://www.neebu.net/~khuon/albums/mavic-ksyrium-tools/PICT0007_001.jpg)

STP??? Not trying to be a wise guy...just be careful. Stress fractures in aluminum are dangerous. 145# ain't bad. I'm 220# and ride a conventional 32H, 3X, Mavic OP (self built) because the stresses are more evenly distributed over the whole rim. When I brake a spoke on a ride I can get off the bike and relieve the tension on the surrounding spokes to further reduce the stresses on the wheel. But as a matter of self preservation I inspect my wheels quarterly with a magnifying glass. Lots of steep mt roads in my neck of the woods...Boulder, CO and I like speed.
I will have to say of all the wheels I've seen yours are the best and only ones I would coinsider...what stops me is the expense.

STP??? Not trying to be a wise guy...just be careful.

I was slightly hesitant about using the wheels for that ride. The problem with Ksyriums is that they don't use standard spokes. My bike shop was unable to get me replacements in time. I had my mechanic and the shop carefully inspect the wheel and they felt confident it would hold. I also felt pretty confident about it. Additionally, the spoke was non-driveside. I have learned my lesson and now carry spares with me as well as the special Mavic spoke wrench needed for them.

http://www.neebu.net/~khuon/albums/carrying_spokes/PICT0002.thumb.jpghttp://www.neebu.net/~khuon/albums/carrying_spokes/PICT0003.thumb.jpghttp://www.neebu.net/~khuon/albums/carrying_spokes/PICT0005.thumb.jpg

What is STP excuse my ignorance? Good idea on the spare spoke and wrench. People laugh at me when I carry the "big" combo tool on rides but they stop laughing when I can fix a broken chain in the wilderness among other fixes. Funny though my bike rarely breaks down (can't remember the last time). Must be an application of Murphy's Law...If I have the tool I won't need it, but if I don't have it, that's when I will need it." Perverse ain't it!

What is STP excuse my ignorance?

STP is the annual Seattle-To-Portland ride. It's around 200 miles.



Good idea on the spare spoke and wrench. People laugh at me when I carry the "big" combo tool on rides but they stop laughing when I can fix a broken chain in the wilderness among other fixes. Funny though my bike rarely breaks down (can't remember the last time). Must be an application of Murphy's Law...If I have the tool I won't need it, but if I don't have it, that's when I will need it." Perverse ain't it!

That's been my experience as well. People tell me I carry too much stuff but I like to be prepared. A lot of my cycling background comes from MTBing and I really can't always expect someone to come rescue me when I break down deep in the woods.

I should have remembered. I lived in Salem, OR in the 1980's and rode up to meet a friend who was doing the ride...So I did the Half/Half STP...I guess. Thanks for the reply. I have a similar background. I bought an original stumpjumper in 1980 and rode it on the logging roads of Oregon for 10 years before I moved to Colorado. More than once I had to dive off the road to avoid one of the maniac logging trucks barrelling down the mt. I laugh when I hear people complain about cars on the highway and harken back to the Oregon woods. Great country where you are. If I wasn't here I'd be there. I would like to do the Ride Oregon someday or the coastal from Astoria to SF. What a hoot!

More than once I had to dive off the road to avoid one of the maniac logging trucks barrelling down the mt. I laugh when I hear people complain about cars on the highway and harken back to the Oregon woods.

I had similar experiences when I lived in Grand Forks, ND. During the fall beat season, the roads were treacherous as kids (literally) would drive the beat harvest trucks rushing from one delivery to another with very little sleep. The more deliveries they could complete, the more money they would get.

. . . Funny though my bike rarely breaks down (can't remember the last time). Must be an application of Murphy's Law...If I have the tool I won't need it, but if I don't have it, that's when I will need it." Perverse ain't it!
I had the opposite experience.

Within a few blocks of leaving the office one evening, I noticed that a front spoke was broken. I returned to the office, took out one of the extra spokes I had just bought, as well as the spoke wrench that had arrived from Performance THAT VERY DAY, and replaced the broken spoke.

I was on the road again 11 minutes after the time I left the office for the first time.

That is usually the case. Lucky it wasn't an outside spoke on the drive side of your rear wheel. Would have been more than 11 minutes. Seriously, it is great when people can work on their own bikes. Its fun!
I was up in the mountains on one of my older bikes and stopped at a store for a coffee before the return ride. There was this dude all decked out in the latest team gear and a new Madone full campy record looking really forlorn. When I asked him why he looked so unhappy he said he had a flat and didn't know how to fix it. He was a converted runner (yea!!!) and had just plunked the money down the day before. I fixed the tire for him giving him my spare tube and using a dollar bill as a patch to fix the cut in the tire. I suggested that he get a good book by Lenard Zinn on mechanics or buy a triple A card for future rides. I also suggested that he get rid of the paper thin tires and buy a couple of armadillos (bullet proof and rideable when flat) until he learned. He was eternally grateful and I hope he followed my obvious sage advice.

That is usually the case. Lucky it wasn't an outside spoke on the drive side of your rear wheel. Would have been more than 11 minutes.

I used to think this too but then I once saw one of the mechanics from my FBS replace a driveside spoke on the road in about five minutes with the wheel still on the bike. He was leading our group on one of our Friday night rides and one of the riders broke a rear spoke. He had the old spoke out in about a minute, strung the new one in place the next and got it tensioned and everything pretty close to true in a couple of minutes. The rider said her brakes pulsated slightly when she lightly applied them but other than that, everything felt fine. I know it was only five minutes because I was on a schedule that day and was watching the clock. It wasn't a permanent fix but it kept the group rolling.