French Creek State Park
Wissahickon
Blue Marsh Lake
Lehigh
Jim Thorpe
Pennypack
etc
Tires? How about the ones on your bike? Tire preference is a personal thing. It has as much to do with your riding style as it does the terrain you're on. I've been riding off-road in Eastern PA for about 13 years, but I still can't tell you what the right tire for you is.
Personally, I like DH tires in the range of 2.3 - 2.4" wide (for XC). I like a grippy tire & low pressure (~20 psi), and I really hate flats. YMMV.
I highly reconemd the trails in Brandywine/ Woodlawn Parks in Northern DE. They have great climbs and about 30 miles of great singletrack. And they are pretty close to SE PA (especially if you live in West Chester!
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