Why you might not want to buy a used carbon fiber bike

I’m a bike shop manager. From time to time, we have customers who bring in used carbon-frame bikes that they have bought online or from a friend. While these cyclists are generally excited about the “deal” they have gotten, they are usually unaware of the number of ways in which they have rolled the dice for something bad to happen.

Here are 4 reasons why it can be a bad idea to buy a used carbon bike:

1. Damage can be invisible. Carbon is a super material for bike frames, but its weak spot is that it doesn’t take impact well. A frame can be cracked or otherwise compromised without showing a thing. Crashes, chain-stay grinds from dropped chains, and other not-unusual types of mishaps can damage the underlying structural carbon of a frame while leaving the more flexible paint and gel coats perfect in appearance. That a frame appears undamaged does not guarantee that it is sound. Which leads us to…
2. The warranty. While most bike companies offer warranties on their carbon frames, those guarantees almost always come with a caveat: the warranty is only good for the original owner. This means that a rider making a claim for a broken frame must supply proof of purchase in the form of a shop receipt or a credit card record. No proof, no warranty. Bought the bike used? No warranty.
3. The crash replacement policy. What is this? Companies often offer affordable replacement policies — 20% off a retail frame price, for example — to customers who have damaged or destroyed their bikes in non-warranty situations. These would include crashes, non-riding accidents, even running their roof-racked bikes into their garage doors (a very common occurrence). Like the warranty, though, the crash replacement price is meant to help those who are a company’s direct customers, not those who have shopped for a bargain on a used bike.
4. The price of add-ons and extras. Buy a good brand of bike from a reputable shop, you’ll get a nice frame with a decent warranty, even a lifetime warranty on the biggest brands. But you also should expect some sort of service package from the shop — a break-in tune-up at least and maybe a discounted service schedule for future work. You can expect a free basic fitting (not just a seat height adjustment), which would generally cost 70 to a hundred dollars or more — yet another added expense for the person who has just bought a used bike on the internet and needs a pro fitting, and that’s assuming that the person has bought the right size bike without professional assistance from a shop.

The crack in this seat stay was the result of backing a bike on a car rack into a fence after a ride. At first, it appeared to be a crack in the gel coat. After 3 rides, it looked like this. The carbon had been compromised and it took a few rides under strain to progress to where the frame was unrideable.

What does all this mean? In addition to the factory warranty against frame malfunctions like cracks or failed bonds, there are other (expensive) ways in which frames can meet their demise. Most major shops can recite a litany of the ways in which they’ve seen customers’ frames abused to the point of failure. At our store, we’ve been brought frames cracked from over-torqued seatposts and mis-installed bearings, one that was damaged when being placed in a work stand, and another that was determined to have received a compromised top tube from being strapped too tightly onto a trunk-mount car rack.

Recently, a customer bought a used high-dollar tri bike from someone in the next state. As it turned out, we discovered when the bike was brought in for service that the original owner had over-torqued and crushed the carbon aero seat post, a “minor” 2 hundred dollar replacement that never should have happened. Also, the carbon aero bar extensions had been sawed off just behind the armrests and had to be replaced; this necessitated the purchase of new extensions worth about a hundred dollars and the price of labor to install them, plus the shifters had to be re-cabled and re-routed, another hundred or so. By the time the customer paid for all of these changes and a pro fit to boot (and still had no warranty), he would have been better off just buying a new bike from the shop, complete with warranty and free tri bike fit. In many of these cases, someone has bought a bike used from a person who was (probably) unaware of the damage, which only became apparent later from the forces of continued usage or when the bike was taken to a shop for routine maintenance.

Any used performance bike is a risk, especially if a buyer isn’t adept at analyzing chain and drive-train wear and tear. Shifters wear out and derailleur springs fatigue, resulting in the loss of crispness and ultimately performance. Parts can be replaced, yes, but when you figure in that kind of expense with the fact that you can’t buy the warranty from the original owner, you have to ask yourself if it’s worth the risk. You make the call.