Mountain Biking - Portland area trails

Hey, I was wondering if any of you guys from the Portland area could recommend good places to ride. I attend University of Portland up by St Johns and get out to Forest Park on occasion, but I was told bikes are only allowed on the logging roads. Fat Tire Farm is a little far to ride on a regular basis.
If there are any really cool places to ride within a half hour I'd also like to know in case I find a friend with a truck who likes to mtb as well.

It is true bikes are only allowed on the fire roads. But from where you are at that is the only place i can think of off the top of my head. Have you tried the north side of forest park? Much more challening and not as many people to deal with (hikers & joggers). Why would you ride to fat tire farm to go there? You can enter the park at several different spots just across the saint johns bridge. You can get in at saltzman rd. off of hwy 30 or go up germantown rd. there are a couple of entrances there. Which ever way you go you will have to start off with a climb. But it is downhill on the way back. You can pick up a map at any lbs. Hope that helps. Maybe i'll see you up there sometime.

Thanks RC. I admit I haven't explored Forest Park real thoroughly, I wanted to get some ideas before I headed back for school. I always go over the St John's, then usually head straight up the hill (what a climb). Before I bought my Trek, I borrowed someones walmart bike and couldn't even get enough traction to go up the hill. It was a long push, but I wouldn't have had the strength to pedal that thing all the way up anyways.