-- Last Updated: Dec-16-12 5:41 PM EST --
Sorry, but I have to take issue here. For the record, I own steel, aluminum, titanium and carbon fiber bikes.
Carbon Fiber (CF):
In terms of strength/weight/stiffness, carbon fiber wins hands-down; metals simply cannot compete. Additionally, you can tailor the stiffness of a CF frame in ways that are simply impossible with metal tubing. From a pure performance standpoint carbon fiber has no equal, which is why essentially all professional racing teams, road and off-road, ride CF bikes. Recently, manufacturers have been putting a lot of emphasis in making CF bikes that are more suitable for recreational riders, for whom comfort is a key consideration. I bought my first CF frame in 1979, the second in 1995 and the third and forth at the end of last season. The evolution of CF has taken a long time, but it's been dramatic.
That said, there are three areas where carbon is less than optimum:
1- Carbon fiber has low abrasion resistance, so it needs to be protected against it. This doesn't seem to be a major issue with bikes, but it could be in the case of a loose/broken spoke causing tire rub on the frame.
2- Carbon fiber has a somewhat unforgiving failure mode. It doesn't dent or bend like metals will, it cracks or breaks. While it's not an issue in normal riding, it can be problematic in accidents.
3- It's expensive, although that seems to be improving slowly. It's likely to get better in the near future, as global carbon fiber production capacity increases.
I loved my titanium bikes and rode them for many years (I still have both frames, in case I ever want to set one up again). Ti is arguably the best of all the metals. It's impervious to rust (unlike steel) or corrosion (unlike aluminum). It doesn't fatigue the way aluminum does. It's lighter than steel, though heavier than aluminum. However, it's much stronger than aluminum, so in frames, there's little difference in weight. It can provide the same type of resilient ride that steel does, with better vibration damping.
The major downside to Ti is the price, which is similar to CF. It can't be built as stiff as CF without being considerably heavier.
Aluminum is the lightest of the three metals and can be built into the lightest metal frames. It's also much cheaper than carbon fiber or Ti. However, aluminum has three significant issues:
- Fatigue is a problem if Al frames are allowed to flex, which forces manufacturers to make their Al frames very stiff, in an effort to extend their fatigue life. That adds weight. I still have my '77 Klein Team Super and it's still in good shape, but it probably only has 10-12K miles on it. I have had a swingarm break on an Al mountain bike.
- Aluminum is only 1/3 as stiff as steel. In order to make a stiff Al frame without making it heavy, you have to use large diameter tubing with thin walls, which makes them prone to denting and "beer can" failures.
- Aluminum will corrode, particularly if it comes into contact with another material such as CF or steel (such as a seatpost). Al-Al joints can also corrode. This can be particularly problematic in coastal areas and when bikes are ridden on salt-covered roads in winter.
Basically, the lighter you make an Al frame, the shorter its lifespan. This is why most Al frames have short warranties. However, recent developments in hydroforming Al have helped to overcome some of its shortcomings and it seems to be gaining some traction in the market again.
Steel it relative inexpensive and has a resilient ride that many riders prefer. It's also popular among people who prefer the "classic" look of skinny tubes. I've owned steel bikes since before AL, Ti and CF hit the market. Steel suffers from some serious disadvantages:
- Steel is the heaviest of the frame materials. In order to make an even reasonably light frame, you have to sacrifice stiffness. It's just not in the same league as the other material when it comes to stiffness-to-weight ratio and never will be.
- Steel rusts, which means you have to paint it and maintain the finish. It also means that you have to be aware of condensation and water infiltration into the seat & chain stays, the seat tube and the bottom bracket. That means using a product like "Frame Saver", which is like automotive rustproofing in a can. The newer stainless steels can eliminate this issue, but at a significant increase in price that puts them in the range of Ti and CF.
While steel lovers are found of claiming that it's experiencing some kind of resurgence, they've been making that claim for decades and it still hasn't happened. While steel is not going away, it's a bit-player in the market and will remain that way.
The bottom line is that people ride whatever they like best in their price range. That often has little to do with performance comparison and everything to do with personal preference.