Check the frame.1 of 9
Carbon frames have become ubiquitous over the past five or so years. While they are lighter, stiffer and more aerodynamic, there are things to worry about. Overall carbon is a tough material, but any cracks or dents can compromise the structural integrity of the bike. Make sure to look over the entire frame, and even take off the wheels and examine over the fork, seat stays and chain stays for any issues before purchasing.
Make sure the frame is the right size.2 of 9
Even though it may be a great deal, you'll end up regretting buying a bike that doesn't fit you appropriately. If you aren't sure what size bike you need, head to your local bike shop and have the experts size you correctly. Riding a bike too big or too small is not only uncomfortable, it's also highly inefficient. Take note that the same size frame will fit differently between brands, so it ultimately comes down to how the bike feels when riding it.
Check if the wheels are true.3 of 9
This one is pretty straightforward—just hold the bike up, spin the wheel and look at its profile from the front. If there's any shimmy in the rolling pattern, you'll need to take the wheel into the bike shop to be trued. While technically not a big deal, it adds additional cost to the bike and may imply that the previous owner put the bike through a lot of stress. Also, be wary of buying a bike with used carbon wheels. Just like the frame, make sure to check for any cracks or structural issues on the rim itself or excessive wear on the braking surface.
Check the hardware.4 of 9
Complete a thorough check for imperfections on any of the bike's metal parts. If you find evidence of rust or corrosion, it's likely due to the bike being stored in improper conditions or excessive sweating on the cockpit/headset. Also, check the bolts to make sure they aren't stripped or broken—especially on the seat post and the cockpit.
Check the components.5 of 9
Old components are usually the first part of a used bike that will break or fail. Remember, not all Shimano or SRAM groupsets are the same. There's a big difference between the 2015 Ultegra build and the 2017 iteration. Check that the groupset is about the same age as the frame, and that the bike isn't a new frame outfitted with old tech. Do your research on the bike make and model before you meet up with the seller—the newer the components, the better.
Check for proper bike maintenance.6 of 9
Is the chain stretched or dirty? Is the cassette caked with gunk? Are teeth worn down on the cassette or chainring? Does the bottom bracket creak when you ride it? Remember, you'll likely have to take a used bike in for a tune up and cleaning, and that can add upwards of $200 to its price point depending on the shop.
Check the source.7 of 9
Online marketplaces like Craigslist and eBay are the two most popular platforms for buying a used bicycle of any kind. eBay has a great customer protection policy that will (mostly) safeguard you from shady dealers and receiving a product that wasn't as described. Always make sure to check the seller's rating and history before purchasing. Craigslist will give you the opportunity to browse local sellers and meet beforehand to try the bike.
Facebook groups are another great place to find used triathlon bikes. Groups like Tri 'n Sell It have proactive members who know what they're talking about and what they're looking for.
First-time buying tips.8 of 9
For anyone looking to buy a triathlon bike for the first time, don't forget that the bike is only a small part of the triathlon gear you'll need. You'll want to include the cost of pedals, shoes, a helmet and more into your overall budget. Also, there's no reason to buy an expensive triathlon-specific bike right away—you can buy a used road bike using the same criteria listed above and outfit it with clip-on aero bars.