1. Are the Tires aired up, and the tread is in good shape? There are no cracks, flat spots, the sidewall is in good condition, etc.
2. Do the wheels spin smoothly? Rim doesn’t hit the brakes, no vibration when rolling.
3. Brakes feel responsive and pull equally.
4. The cables are clean, and the housing is not cracked.
5. Frame and fork have no cracks, significant dings, bubbling paint, or stickers that may be hiding something. Plus, bring a rag and cleaner to wipe down the frame. Dirt hid two racked frames that I bought.
6. Measure the chain with a ruler. Pins should match up to the inches. Not super precise, but will let you know if the chain needs to be replaced.
7. Check derailleurs for scrapes and impacts, plus the jockey pulleys.
8. It should shift smoothly and hit all gears during the test ride.
9. Make sure the headset is smooth and not loose.
10. Make sure the Bar Tape/ Grips and seat are in good shape.
11. If you can’t test ride it, do NOT buy it!
12. Rim is flat at the braking surface. Not Concave.
13. Pull the chain off and see how smooth the crankset spins. Should not feel any vibration.
14. Pull the Seatpost out all the way. Make sure it has a height limit line and has not been cut.
15. Make sure the seat binder bolt can be tightened.
16. Look at the stem and double-check the spacing. Steerer tube is be underneath the binder bolt.
17. Flip the bike upside down and check if there is a serial number.
18. While upside down, check for dings and cracks.
19. Bring a cloth and some cleaning spray, and clean any dirty spots for damage.
20. Double check the size with a ruler if there is no size sicker.