1. Bikes must be 38 pounds or less.
2. Designated tire size must be less than 2.5.
3. Front shock must have less than 7.5 inches of travel.
4. Bikes must have at least two chain rings unless they are single speed.
They are strict on enforcing #s 1 and 2. If your bike happens to be more than 38 lbs, they will still let you ride for the day, but will be told not bring back the same bike. As for #s 3 and 4, not really enforced. We saw DH bikes all day, and a couple of us rode w/ single chain-rings w/o any comments from the folks loading the bikes.
Bring spare tires, my tires were cut and slashed in a few places from the sharp rocks.