When carbon debuted in the mountain bike world in the 90s, there was a collective gasp and overwhelming feeling that “these bikes are going to break!” That may have been true in the beginning, but it is no longer the case. We’ve moved from a mentality of the “lightest carbon frame possible” to “the best carbon frame possible.” With a switch of focus from light to durable and building carbon frames to withstand the abuses of a specific genre, we’ve seen carbon become nearly ubiquitous in all forms of cycling as the material of the pros. While a carbon frame built for cross-country riding may not hold up as well as one built for downhill, the lightness of the cross-country frame is more important, while the durability of the downhill frame is a more significant asset.
In truth, if we tested the strength of the same frame built from carbon and aluminum, you would see that carbon fiber frames are much stronger per pound in terms of both stress tests and impact tests.
Weight vs Price
One of the most discussed aspects of carbon fiber frames is the weight savings over aluminum frames. It is hard to pin down a hard and fast rule about how much lighter a carbon frame is compared to an aluminum one. For example, a Santa Cruz Bronson carbon frame may boast a 1.5-pound weight saving over the aluminum version while the carbon Pivot Switchblade might be 1.9-pounds lighter than the aluminum Switchblade.
That begs the obvious question, is a 1.5-pound weight saving worth the extra cash? That, of course, is a personal question that depends on your goals and finances. It should be noted that component upgrades save weight as well. Even if you had a chunky aluminum frame, it is easy to save a pound or two with the components on the bike.
The myth that carbon is fragile again rears it’s ugly head, but it is just a myth. While both frame materials are susceptible to catastrophic failure, carbon fiber frames tend to be stronger per pound than their aluminum equivalents. We see a lot of pictures of broken carbon frames pasted into forums to try and show how fragile carbon is, but it’s just not the case. We don’t know if these people have ties to aluminum investments or if they hold on to bygone beliefs about carbon, but what we do know is that carbon frames are stronger and lighter than aluminum, simple as that.
As technology changes so quickly in the modern era of mountain biking, we don’t know how much lifespan will affect your choice, because either material will give you a solid 7-10 years of life, but if you really want to buy a bike that is going to last, carbon is the way to go. Impacts and abuse aside, carbon doesn’t fatigue over time and your frame will be as good in 20 years as it was the day you bought it, although heckling will probably increase, as might your belly.