Aluminum metal fatigue

One of the nice properties of aluminum alloy is that for a metal, it is relatively light in weight. Light weight is valued by bicycle manufacturers and riders. One of the not so good properties of aluminum is that when it eventually wears out and breaks, it often does so with little or no warning. It does not bend or deform very much- it just snaps.

While cycling to work this morning, I felt a vaguely familiar, but disconcerting feeling. For just a moment, the bike did not feel right. Something moved in a way that was not normal. I remember feeling that sensation before, but could not remember til later where and when this happened. At first I thought I had a flat tire, but a quick check showed that the tires, while perhaps a little bit less inflated than usual, were still in good shape. I continued on to work with no further issues (other than a little drizzle) and, as I often do, I pedaled hard up the final incline (stressing the bike with each pedal stroke) before the final down grade into work. No noticeable problems. Everything seemed fine.

On the way home, I had a tailwind during the long decline along Irvine Boulevard by the old El Toro Marine Airbase. I pedaled hard again, probably reaching 35 mph in a bike lane alongside a 4-lane highway with traffic traveling at freeway speeds. To the right is a ditch filled with jagged rocks which carries the water runoff when it rains.

As I pulled away from the stoplight at the intersection of Irvine Boulevard and Tustin Avenue, a few miles closer to home, I pulled on the handlebars like I normally do to enable me to transmit power to the pedals. I felt something move in the handlebars. I thought my aerobar might be slipping where it connects to the handlebars. This has happened before. After the fact I realized that this was a bad diagnosis, as I had not been holding onto the aerobars, but rather was holding onto the brake hoods on the top of the handlebars. I slowed and turned right onto a low traffic street called Plaza Drive located between Tustin Avenue and where I normally turn on Holt. I made sure there were no other cars around and then slowed to about 5 mph while I slowly tried to wiggle the handle bars and watched carefully to see if I could detect where the motion was happening. When I gave a slight tug upward, the entire handlebar assembly snapped off in my hands without warning, causing me to loose my balance. With nothing to grab onto other than the handlebars already in my hands, I tumbled forward over the front wheel, landing on my head and shoulder in the middle of the road, with bike parts landing all around me. I hate that feeling of knowing that I am about to crash and there is nothing I can do about it but fall.

After I picked myself up and collected all the bike pieces out of the road and moved them to the curb, I I took some photos of the broken bicycle and called home for a ride. Then I realized how very blessed I was that this mechanical failure had happened when I was going 5 mph instead of a few minutes earlier when I was going 35 mph. If the failure had occurred on that busy stretch of Irvine Boulevard with fast traffic on my left and a rocky ditch to my right, I would most likely have been seriously injured or killed. I knelt and thanked God for having answered our prayer earlier that morning before leaving home that I would be protected while commuting to and from work.

I always wear a helmet when riding a bicycle. This was only the 3rd time I have needed it, but I have sure been glad that it was securely fastened on my head each time, or I might not have survived to write this blog posting. I was also wearing gloves, which helped minimize the damage to my hands, even though they are still stiff and sore from landing on my clenched knuckles that were holding onto the detached handlebars. My right shoulder has a good size raspberry (road rash), has a deep tissue bruise, and is sore. I will probably be sore all over in the morning. But I am very grateful to be alive and in one piece.

BEFORE PICTURE: (click on photos to view larger image)



AFTER PICTURES:

The frame on my 2003 Lemond Tourmalet bicycle is made from Reynolds 853 steel tubing. According to this website (http://tinyurl.com/yllexhp), the front forks are Bontrager Race Carbon fiber. As you can see from the photos, the top portion of the aluminum fork steering tube snapped off just below where the handlebar stem was connected.

After the fact, I remembered that the last time I felt a bike moving in an unnatural way was years ago when the chain stay portion of the rear frame triangle on my old bike broke where it connects to the rear wheel dropouts. This allowed the rear triangle and wheel to move slightly. While cycling to work, I had probably sensed the aluminum steering tube starting to fail.

So all you cyclists out there, if you are riding an older bike with a frame or load bearing components made from aluminum, you should periodically check them to make sure they not approaching the point of metal fatigue failure. Look for cracks periodically and give them a good tug before each ride to ensure they are still solid.