Many people buy bicycles without checking on the warranty provided for the frame or its components. Eg, I have customers requesting us to repair their hydraulic disc brake and gears on their new bicycle which should still be under warranty.
If you want to buy used bicycles with carbon frames, find one from companies that offer the best warranty. Eg, manufacturers from China like XDS, provides 3 years warranty on their carbon frames and 5 years warranty on their alloy frames for the original owner. Trek offers only 2 years warranty for carbon frame but lifetime warranty on other type of frames. I read that they also have a loyalty program, whereby they will offer a discount to replace damaged carbon frame.
These warranties are for manufacturing defects, so the warranty will be voided if you have an accident which damaged the frame. However, companies like Calfee provide 10 years warranty for carbon frame repairs from the original date of service. They will even perform an inspection for second buyers of their used frame and perform any repairs which are covered under warranty at no additional charge.
So, if you still intend to buy used carbon frame bike, you may want to check with the owner the kind of warranty he still holds for the carbon frame. Then you will have to negotiate with the seller to see if there is a way you can get him to assist you in getting this warranty claim should you face a problem after riding it.
Note though that you may like the carbon frame but not like the components already installed. The next question to ask the seller or discover for yourself is whether you will be able to find spare parts for its components during repairs. It will be time consuming and costly for you to replace parts that are difficult to find, especially if you intend to maintain a complete groupset.
