Super fast downhill through a dry (usually) creekbed. It has huge bank turns around every corner, just like a bobsled, hence the name!
Park at Popperton park, then head east. Go through the gate for the private community, then 100 yards later, head down the trail to dry creek. Ride up through dry creek on the Bonneville Shoreline Trail for a few miles. When you arrive at a sign that says no bikes overlooking city creek, go left down the nasty looking steep hill. The bobsled starts here!
http://www.singletracks.com/item.php?c=1&i=1983