Originally Posted by
CliffordK
I've started using cassettes on most of my bikes.
However, overall you need very little space between the cassette/freewheel and the dropouts/seat stays....
It all depends on the design on the drive side stays at the dropout end. Many frames have this area relieved to provide more clearance. Non-relieved stays are more common on older and lower end models, as relieving the stays was an additional cost. Often, when upgrading such a bicycle with a wider freewheel, there is sufficient clearance to install the freewheel and mount the chain but the chain jams against the non-relieved seat stay during shifts into or out of the small cog.