Downingtown is a great area to bike. Why? Road Biking BicyclePA route L goes straight through Downingtown following 322 and 282. The Tour of Pennsylvania stage 2 start is in Downingtown.
Mountain Biking Marsh Creek State Park - Many miles of trails. They host a race in October. Harmony Hill (Currently open but still under construction) This is an important location for cycling. It is being designed by mountain bikers for mountain bikers and is also a pilot for other nature parks in the area.