Mountain Biking around Fongyuan or Taichung?

Anyone have any favorite mountain biking spots they are willing to disclose within reasonable distance of Fongyuan or Taichung? It’s still a ways off, but I was thinking next time I’m in Taiwan I may try and get away from the in-laws to do a little biking (not that shopping and playing with babies isn’t fun or anything).

Also, on a related note, anyone know about bike rentals? The in-laws have a serviceable low-end Giant, but it’d be nice to have something a little more heavy duty.