Chain/Drivetrain Wear

Invest $10 in a chain wear tool. Use it to check chain wear. If the chain is at or near 75% proceed with caution. Once chains go past 75% they start to wear the freewheel/cassette and eventually the chainrings.

Ride the bike (if it’s rideable) and test each gear. If the shifting is out of tune this may be difficult. Pedal hard in each gear, if there’s any slip that allows the pedals to jump forward it’s a sign the rear freewheel/cassette is worn, or the chain is worn past 75%.

The chain wear tool I use the most is the Park Tool CC-3.2. It shows 50% and 75% wear. It’s technically not as accurate as the Shimano TL-CN41, but it’s 1/3 the cost.