I had my chain come off the cassette a couple of times yesterday on my road bike, wedging the chain between the cassette and the seatstay. Both times were on descents where I hit either a large pothole or a speedbump (so it’s not overshifting). I’m guessing I need a couple more links out of the chain to make it a little tighter but before I take them out I wanted the hivemind opinion. Am I right or is it something else? The mech, chain, cassette and crankset are new so I’d expect the springs etc to be fine still.

Have you set the rear mech limit screws correctly ? [have a look HERE]

To get the correct chain length – wrap the chain around the largest cog on the cassette and the largest chainring – without going through the rear mech – make note of where the nearest link is that the chain could be joined and add two links. If you feel this is too slack remove one link.

I’d also have a look at the rear mech and make sure it has tension.