The Great Western Trail skirts Mount Timpanogos on its way from American Fork Canyon to Provo Canyon. This section is also called the Mount Timpanogos Perimeter Trail. This is a narrow singletrack with some steep climbs and many rough sections, but with beautiful scenery that makes it all worth while. I'd rate this trail advanced technical and strenuous aerobic. Altitude gain is 1300 feet. Because the trail intersects the Timpooneke Road at three locations, you can bail out any time for a shorter ride. The ride I describe here is 15 miles round trip.
After one mile comes your first chance to bail out onto Timpooneke Road. Just catch a trail heading right when you reach the bridge over the small creek.
If you took one of several doubletrack connectors out to Timpooneke Road, you may need to turn and peddle south (left) a little ways along the road. Look for the descent into Rock Canyon at GPS N 40° 26.061' W 111° 39.937' on your right. (Watch carefully! It's very easy to miss it.) Don't worry, it's not as steep coming up the other side.
Or, continue on from the end of the Timpooneke Road, on the Battle Creek Trail as it head south towards the saddle behind Big Baldy. Ride up the switchbacks behind Big Baldy, then drop 3000 feet over 5 miles into Provo Canyon at Canyon Glen.
Getting there: From I-15, take the Alpine-Highland exit and drive 7 miles to the mouth of American Fork Canyon. Pay your $6 fee (as of 2009) there. Five miles later at the fork in the road, go along the south fork of the river. About 4 miles up, there's a T in the road. Turn right into the Timpooneke Campground road. The parking area is on your left about 1/4 mile later.
Single-page riding guide
GPS track files (right-click and "Save as..."):
GPX GWT (Timp Perimeter)
GPS track file of Timpooneke Road
High-res topo (700 KB): View map
Lodging, camping, shops: Links to north Utah County resources