I've added two of my favourite rides from Frankston to bikely.com :
http://www.bikely.com/maps/bike-path/Frankston-Loop-Hastings
http://www.bikely.com/maps/bike-path/Frankston-Loop-Mornington
It seems to me that lots of people ride around Frankston, but they
mostly ride up and down Nepean Highway. Which is great if you want to
ride with the pack. But there are many other great places to ride.
These start and finish at Frankston railway station.