Is there such a thing as frame failure?

Question

Several general questions have been asked regarding how long a bike or bike frame will "last", and the gist of answers seems to be that a bike can last quite a while of the replaceable components are replaced and the bike is reasonably well maintained.

But what about the inherent structural integrity of the frame itself? Is there such a thing as a risk of sudden frame failure or disintegration after some level of use? Do bikes ever fall apart, or develop a risk of breaking or fracturing along weak points? One of my bikes has more miles on it than the car I'm turning in — and I wonder about the integrity of the car!

Answer 1

Yes, frames do fail even if they're not crashed or ridden excessively harshly. The only way to mitigate this problem is to inspect the frame regularly during your maintenance and cleaning. Look for cracks. When riding, pay attention to creaks and squeeks and always find the root cause (it could be a crack).

Keep in mind that:

• A bad weld could hold fine for years before coming apart.

• Unchecked rust can eat through steel tubes, either from the outside-in or the inside-out. Once it starts, you have to keep on top of it or it will eventually take the frame. Rust also seems to have "good taste" in tubing by preferring the pretty Italian stuff to, say, gas-pipe schwinn.

• Metal fatigue can form cracks that grow slowly until the frame suddenly snaps (I've seen this personally where the chainstay meets the dropout, and on crank arms).

Aluminum is the worst culprit for fatigue cracks. Aluminum seatposts and steerer tubes also have a tendency to develop aluminum oxide blooms that may permanently jam the seatube/steerer-tube in the frame.

Carbon typically won't survive a bad-enough crash. I've heard of long-term delamination issues, but never saw one personally. AFAIK every carbon frame "dies" in a crash or mishap that damages the frame to the point where the owner no longer trusts it. Anyone have stories about what happens to carbon that is not crashed?

For a concrete example, below is my own failure from a few years ago. It happened as I was cresting a very steep hill. I heard a loud "pop" and didn't realize what happened until I looked around and saw the chainstay separate from the dropout with each pedal stroke. This is a steel bike and was totally repairable, BTW. I didn't crash as a result (but neither was I going fast). Note the little bit of rust visible at the top of the crack. It indicates that the crack had been there for some time before the total failure.

Answer 2

Yes - frames are subject to wear, tear, aging and fatigue. The primary area of concern or failure on most frames is at the bottom bracket. On both metal and carbon frames this is a point of high stress and flex. But any weld or joint is subject to stress and may fail over time.

You should periodically inspect the whole frame, paying particular attention to and weld-points or joints. Look closely for signs of paint or weld cracking as well as any rust on steel frames. The best way to do this is to hand wash the frame and inspect it as you go. If you want it to last even longer apply a layer of bike or car wax your frame every six months or so. Wax makes it harder for dirt and mud to stick to your frame, and will make the next clean easier.

That said, if you make it a habit to clean and inspect your frame, are an 'average' rider (not excessively heavy or riding aggressively off jumps and drops), store the bike properly and care for it well it could conceivable outlive you.

Answer 3

What you are referring to is sometimes known as catastrophic failure, when a frame fails under load. While this does happen from time to time, it's relatively rare. There are tales of defective carbon frames failing spontaneously while riding, but these seem to always be friend-of-a-friend stories. Most frames that do "fail" do so because of traffic accidents or other damage. And, as Gary points out, the bottom bracket (and mounting eyelets) are likely areas to wear.

Frame material also plays a part in this. Conventional wisdom in cycling circles is that steel is the most durable - it can be bent back into shape and even re-welded. Aluminum frames can't. And carbon fiber frames have a reputation for being delicate; if one of those breaks, you throw it out and get a new one, since any fixes will be unreliable.

While there is some truth to this, steel can be damaged to the point where it would be unsafe to fix and re-use. And carbon fiber is more durable than folks assume. But evaluating a damaged frame is often more trouble than simply replacing it. There are pro wrenchers who can do this kind of evaluation based on experience, but without putting the frame through an x-ray machine can you really, definitively say that a frame is safe to put your weight on after it's been bent and re-welded?

In general, yes, the frame is the most durable part of the bike. But it, too can be damaged beyond repair.

Answer 4

I have seen a few old steel frames that failed. In one case the down tube cracked in two at the point where the down-tube-mounted shifters were attached. In another case the crack was at the junction between down tube and bottom bracket. I've also seen seat stays separated at the seat tube.

But all of these failures occurred on bikes that had quite obviously been left out in the rain for years (if not decades), and all of them were still being ridden, even with the broken frame. The traditional steel "diamond" frame is extraordinarily robust.

Answer 5

I managed to break a steel frame about 2 years after buying it. That did involve a crash a year after owning it and then riding it to destruction though. I noticed after the crash (into a ditch) that the geometry felt shorter and tighter. I just carried on riding it though. In hind sight that might not have been the most intelligent thing to do.