I have a 2013 Trek 7.1FX. My chain wear tool dropped right in so I thought it was time to replace the chain. The existing chain is marked "KMC Z Narrow". I thought I did my research and ordered a KMC 51 chain. It is also marked "KMC Z Narrow" on the chain itself.

The master link looks fully engaged and it rotates freely at both ends after I installed it. On my entire 10 mile ride yesterday the chain "skipped" or it seemed to miss a tooth every now and then in the rear. (7 speed). It never did this before with the old chain. The chain never jumped off but it was extremely annoying and something just isn't right.

I guess I can take the master link off of the new chain and use the old chain until I figure this out but that's not where I need to be. Did I buy the wrong chain or what suggestions do you have?

Front: Suntour XCC, 48/38/28
Rear: Was...MF-TZ31 7 speed 14/34 and replaced last year with DNP Epoch Freewheel 7spd 11-32. No issues with either Freewheel with the old chain.


Thanks.