Exploding cassette

term1te

Riding to work this morning when I slowed down approaching a roundabout, changing from the larger to the smaller chain ring. When I stood on the pedals to move on to the roundabout there was no resistance, I wobbled and only just managed to stay upright with my left foot trapped between the frame, just under the bottle cage, and the left crank. I hopped to the side of the road, released my foot and found that one of the sprockets on the cassette and disintegrated. Veloce 10 speed, with the 4th sprocket now in about 10 small pieces. Fortunately I wasn't too far from home, so lifted the chain onto one of the smaller sprockets and very slowly cycled back.

I don't think the cassette was lose, there was no creaking or apparent play in it before hand. I was going quite slowly (fortunately) and don't think I put that much pressure on the crank when it gave way. The chain wasn't particularly crossed, being in the middle of the cassette. The chain and cassette have only done about 3000 km over the last 18 months and showed no sign of wear. So what could have caused this?

6wheels

They probably heat treat the sprockets to increase longevity, seems as though something in the process has gone wrong or the material is crap or combination of both.

The Rookie

Consumer rights act seems to apply if you want the same again!

I agree with the above, it sounds like the surface hardening (to reduce wear from the chain rollers) has gone to deep leaving the sprocket too brittle and prone to the failure you had.

Matthewfalle

It just broke. A SRAM one did the same to me so I took it off, hit it with a hammer and threw it into next door's garden. Just one of those things.