I have been looking for "bike number 2" and have thinking of getting something slightly modern than my 1970s Italian steel bike.

I have my eye on an early 90s Cannondale with an Aluminum 3.0 frame. Then I start to read that aluminum frames will eventually fail over time, which is giving me second thoughts about getting one.

Should I be worried about this as long as the bike is in good condition? Is there a certain time period after which aluminum bikes should be avoided (10 years? 20?)

i think the real issue is what kind of mileage it has on it and if there is any damage to the frame.

age shouldn't matter too much.

Supposedly it wasn't ridden much at all, though I have yet to set it in person.

My next question would be, if I put 50-100 miles on it per week, how long could I reasonably expect it to last?

Any frame material is likely to fail over time. Steel rusts, y'know.... As long as you don't see any cracks it should be fine. I'd do a basic visual inspection of any bike I use, of any age, on a regular basis -- every 1000 miles or so. It will still likely outlast your usage / ownership of the bike.

The only material I'd have any real concern over would be 1st generation carbon fiber. I believe they understand CF much better these days as a frame material.

As part of their design, aluminum frames are generally "overbuilt;" this is what gives them their inherently stiff ride quality. I've beaten the heck out of enough aluminum mountain bike frames, without problems, to know that a quality aluminum frame is plenty strong and durable enough for anything that I'm likely to throw at it. Regardless, the big thing with aluminum frames is knowing that since aluminum doesn't have a fatigue limit, any and all stresses an aluminum frame encounters puts it a little closer to failure. Steel has a fatigue limit, so at least some of the stresses a steel frame encounters do not put it closer to failure. That being said, steel frames can fatigue and fail, too.

FWIW, I've bought a bunch of bikes in my life, but never a used aluminum-framed one. To each their own-

I understand that steel is not everlasting either. I guess it's a matter of perception. When I think of steel, I think things like skyscrapers and tanks. When I think of aluminum it's soda cans and Reynolds wrap.

Aluminum's fatigue characteristics don't just apply to frames, but all aluminum alloy components. If you're going to fear aluminum frames, you may as well forget about riding any bicycle with aluminum components.

Well, that's the point. I'm trying to figure out if I should fear them. I didn't until I started reading some things that were posted on this very forum.

And frankly, the thought of my top tube suddenly cracking in half scares me a lot more than having a crank break.

i agree. i have seen some aluminum framed bikes last a long long time. i wouldnt be too worried about it unless the frame looks like its been through hell.
i too would shy away from carbon bikes, esp. old ones. the new ones seem to be good, but i will always be spooked. i have seen carbon fiber at its worse. its usually a pretty catastrophic failure.

But the chances are much greater you could be run down by a truck.

Steel truck or aluminum?

I have never seen a Cannondale frame fail due to fatigue. Cannondales are very stiff, and they have plenty of safety factor built in. These factors minimize the impact of cyclic frame flexing in terms of causing fatigue over time, because fatigue is influenced by how much aluminum flexes, not just how many times it flexes. I am 250lb, and I hammered the heck out of my 1986 63cm Cannondale for ~20 years. The only reason I stopped riding it was that I went to bigger frames to make my aging body happy. The old C'dale is still hanging in my garage, as strong and stiff as it was the day I bought it. Granted, my first-generation C'dale frame is even more resistant to fatigue than a 3.0 frame, but the 3.0 frames are plenty over-built as well. They should last many, many tens-of-thousands of miles.

Yes, aluminum will fatigue over time with repeated flexing, BUT a good frame designer can push the number of cycles out into the BILLIONS before the frame fatigues significantly. Note the importance of the word "good" in that sentence. Cannondales will last a lot longer than say, old aluminum Alans or Vitus/Bador frames (or even the old, glued Treks).

- FBB

Thanks, this is exactly what I wanted to hear.

what happens while it fatigues? does it just it just lose some responsivness over time? for example, can you feel a worn out frame just by riding it? does a frame with 15,000 miles feel less snappy than the same frame with 100 miles? so many questions....

The flip side of a stiff aluminum frame is the ride quality.

I had a early 90's all aluminum Trek 1500. It was a fantastic riding bike, up to about 30 miles or so. Past that, it got very uncomfortable to ride. I couldn't imagine spending the day on it.

Newer aluminum frames ride significantly better - partly because the construction/geometry has evolved and has been refined, and partly because of the use of CF stays and forks.

I'll not ride a "vintage" all aluminum bike again, if I have a choice about it.

Aluminum is not very elastic - when it fatigues, it cracks.

Aluminum as a material, I think, is plenty strong for bike duty. Hell, they've made aircraft from aluminum for years. Some of the greatest war birds were aluminum (think WWII comes to mind).

I think what to look for is the quality of the aluminum alloy and signs of wear on the frame. Each bike is a little different when used because each is exposed to different wear. I agree with the posts above that emphasize inspecting the thing and being familiar with this particular bike.

It's also a taste thing- I prefer steel to any other material, but some people really like good aluminum alloy.

What he said. Often, welded aluminum structures will start showing signs of fatigue by developing cracks in the weld beads.

- FBB

Why worry about just frames? How about aluminum stems, bars, cranks, seat posts and rims?

TCS

Either situation would likely have unpleasant results.

Cracking is the very definition of fatigue failure for any material. The cracks initiate in different materials in different ways and for different reasons and then propogate at different speeds.

The fear factor that anti-aluminum folks toss around is that the cracks propogate faster in aluminum so there will be less warning of an impending failure than there would be for steel or Ti - it's not an unfounded concern but it is largely over-stated.

This is a good point. I had one of the first generation Klein Quantums and I feel lucky to still have teeth. It beat the heck out of me. But as far as wearing out I think any of the older Kleins or Cannondales would outlive any of us as long as they weren't damaged in any way.

I agree about the feel of aluminum- it feels less comfortable to me than steel. I'm not sure what exactly it is, but I just could never grow to like the ride of the aluminum bikes I've ridden. I keep coming back to the basic Raleigh or Schwinn steel frames- they're heavy, but seem to have a nice ride to them.

True enough. Some material (like steel) is elastic enough that it will bend and stretch a bit before cracking and ultimately failing. But I suppose that is just the cracking process manifested in a different way.

What I meant to convey is that aluminum, not being very elastic, will crack faster and fail quicker when it reaches it's fatigue point. You might "feel" a steel bike ride differently before failure - an aluminum one will probably just crack and ulimately fail without noticeable warning.

In any case, I side with you - the fear factor is oftimes overstated. I would have no problen riding an aluminum bike, aside from ride characteristic issues (personal taste). To me, the older ones tend to ride harsher than I like (in general), but I've ridden some really nice newer ones. I'm particularly fond of the Klein Reve' (not sure if it is in production any more, but I loved the way the 2005 one I rode handled).

Likewise, the danger hype for CF bikes is pretty much nonsense. CF is very, very strong, and there are A LOT of the old Trek glued ones running about. If you're stressing CF to failure, you're probably crashing at high speed and have other fish to fry......

I have a '99 Cannondale R1000 66cm bike and what I like most about it is the lightness of it!

My other bikes are made of steel and I LOVE them, but if I'm going on a long, hilly ride I prefer the 'dale.....I do check it regularly at the welds for any signs of cracking...I've heard the stories too, but I've yet to find any signs of "stress" on any of the 3 'dales I've owned over the years.....