I recently purchased a second hand rubi ts30m and find its not great on porcelain because the breaker is very close to the top of the tile. Am I doing something wrong?
Do the breakers wear out?

Delayed reply:

The breakers don't usually give up, you snap them if you're giving it too much on a heavy tile which is why they made the TS Plus range which has a stronger breaker.

Some porcelain just doesn't cut on a dry cutter as a dry cutter is designed to score a glaze and allow the biscuit on the back of the tile to follow the score line and break accurately and neat. Your fully vitrified (full bodied) porcelains don't have a glaze to score, nor a biscuit to snap, they're just tough buggers that need wet cutting.

It may be that the breaker is not up to the job - some of the more expensive, larger cutters have more breaking force

Nah, it's a TS30, it's made for walling really.

Get a TS plus - better breakers