West of Boulder, the Betasso Preserve has the Canyon Loop Trail which is open to mountain bike riding. The actual mileage of trail riding on this lollypop-style loop is pretty short, maybe 3.5 miles overall. It seems like uphill the whole way at times. Coming from Boulder, the trail starts on Boulder Canyon Road and heads steeply up a mile on a very loose rocky route. For many, this is both a challenging uphill and a challenging downhill (maybe a hike-a-bike both ways!). The top section of this climb is alittle better than the lower section. Once at the top, this access trail intersects the loop portion of the trail. If you go counterclockwise, it has a very quick downhill, and then it just seems to climb for 90 percent of the loop. Its not very satisfying.
To reach the trail from downtown Boulder, head west on the Boulder Creek pathway into Boulder Canyon. Continue west on the pathway to its end. Continue on the road for about 0.75 miles to the trailhead parking area on the righthand side just before the tunnel.