Ah yes I would go with what Stewart suggests then the tangents will always be linear by default.

This always bites me in the butt and then I have to spend a bunch of time remembering how to fix it. It seems I use linear tangents much more then parabolic.

This is one of those things they changed from earlier versions of maya as I definately recall there being an ease in and ease out setting which I no longer see in maya 2013