Failure Mode

That long silver line on that bar is a crack. Found on MG's personal rig recently.

Failure is a topic that many of us that ride bicycles don't like to speak of. It is "negative", so you just do not speak of failure in terms of your performance. However; there is another kind of failure that we do not speak of much either. Failure of components and frames and forks. It is a very real possibility every time you ride your bicycle.

I was tipped off to a very good article covering a wide array of the topics related to parts failures on bicycles by a Twitter/blog reader contact I have. The article is by "Cyclingtips" and can be found by clicking this link. It is well written and broad based in scope. So, I feel it is a good primer on the subject for any cyclist.

I am going to take a look at this from a mechanic's/rider point of view. The above link does a good job of pointing out a little bit of the following, but like any broad ranging topic, there just wasn't room there to flesh out the subject. Not from a point of view such as mine, which includes being a mechanic for over 20 years.

In terms of parts and frame failures, we see a lot more crash related failures than we do the type of failure that happens from "life span" issues. Generally speaking, you can chalk that up to what the linked article points out where bicycles are sold then never really used. Crashes can constitute a lot of examples. The obvious is where there is something catastrophic, where bodily injury was inflicted, or there was obvious violent contact with something. (Roof mounted bike into a garage door, as an example.) However; I feel the most commonly found failure is due to a crash that did not seem to be a big deal at the time, but resulted in a failed component later.

Things will last only so long, then they die.....

This can be hard to pinpoint because most of the time people file away little biffs and dings in their mental recycle bin never to be retrieved again. However; it can take only one fall to precipitate a crack in a handle bar, as a for instance, that could lead to a "catastrophic failure" later. See MG's handle bar above. He dumped his bike in a corner, then later found this crack. Had he not seen that, the bar could have "given away all at once", or so it would have seemed. The reality was that the damage was already there waiting to fail the rest of the way.

I like to think of these things in terms of something that happened back in my youth when I was a jeweler. We worked on fine jewelry and manufactured custom designs which required lots of polishing to bring the fine metals up to their highest glow and sheen. To clean everything up, we used an ultrasonic cleaner, then a hot, high pressure steam bath. We would use these heavy stainless steel "tweezers" to hold the items as we blasted them with shots of steam. After we were finished, we would nonchalantly toss the tweezers into this heavy glass container we kept on the back drip edge of the sink. One late night, after one more of probably hundreds of thousands of tosses of tweezers into that glass, I sat down after cleaning something up to file it away in its envelope and move on to the next task. It was maybe 3-5 minutes later when the glass exploded into thousands of tiny crumbs.

I like to think of that last tweezers toss as the final crash that "broke the camel's back", as it were. The glass continued doing its job for a few more minutes, then it "just failed". In reality, every toss of those metal tweezers was building up stress in the glass which finally resulted in the glass exploding in spectacular fashion without seeming to have any "input" to make it do so.  Our bicycle parts, frames, and forks are also subject to these stresses that can eventually lead to a part failure, like the wheel I have shown here. That pulled through spoke probably had a crack next to it to begin with before it actually failed completely. Had the owner of that bike seen that crack beforehand, he could have replaced the wheel before it completely failed.

Considering that most riders almost never inspect their bicycles for cracks or loose fasteners, it is a near miracle that we don't have more catastrophic injuries related to "JRA" (Just Riding Along) incidents. Consider also that hundreds of thousands of bicycles get infused into the marketplace every year. The sheer numbers of bicycles waiting to fail must be astronomic in total. That isn't to say that efforts should not be made to improve things, but we are talking about a small number compared to what it could be, in my opinion.

Fat bikes, in particular, have had a rash of fork issues since becoming widely available.

Another thing that has been a noted issue with failure, but not a high frequency thing, is the advent of rigid fork fat bikes. The forces at work which exert stress on different parts of a fat bike are far greater, or different, (or likely both), and have caused forks to be recalled. We've seen some subtle and some not so subtle redesigns of fat bike forks which we have replaced under warranty. Obviously, this will sort itself out, but missing the mark on design is another way we've seen failures on parts.

Even less likely is the rider who refuses to repair, or replace an obviously compromised part. While this is admittedly a smaller fraction of possible failures, I see this far more often than I do the flawed part that just falls apart. At any rate, these types of situations concern me the most. In fact, I will refuse a job, rather than take the risk that something will continue to perform without causing injury or death. A famous example would be the various jobs I have refused because the steel fork was bent backward and the owner refused to replace it. Sure......it is steel, and as one guy said, "I've been riding it this way for 30 years!". I replied, "All the more reason I would not work on that. Your luck is due to run out at any time now.", and I wasn't about to take a bet on that one! He probably is still riding that bike, but you know, the minute I work on it, guess what would happen....

Finally, there is the misuse of parts and bicycles. We see this a lot! Stems and seat posts extended beyond their intended insertion points, quick release levers used incorrectly, trailers loaded with cargoes way in excess of what brake and wheel systems on the bicycles that pull them were rated to. Racks affixed to carbon fiber seat posts, bags installed incorrectly, and the list goes on. It is amazing to me how much of this people get away with without catastrophic failures. So, there are another group of potential failures just waiting to happen.

The point is, "life cycle" product limitations may be something worth pursuing, but don't for a second think that this will solve the potential issues with failures. There are far more modes of failure than that.