Chain popping on hills

[Guest]

My chain never came off my current bike before, but recently it did and now when ever I go uphill or pedal from a cold start my chain pops and my pedals kick forward like there's no tension and then my chain catches and I go on my way. It's been doing it more and more frequently. What's going on?
Thanks for your help, Robby

[Alex Ramon]

Hi Robby,
It sounds like your chain and rear sprockets (cassette or freewheel) are worn. They'll start slipping when the chain stretches and the rear sprocket teeth spread apart. Both of these components usually wear together, but sometimes you can get away with just replacing the chain. Don't worry about the front chainrings... it usually takes them more than twice as long to wear because the are bigger diameter.

[Alex Ramon]

Here's a new a video that shows how to check for chain wear.