It's the desert. It's either hot or cold. Bring water.
Start to Zion Curtain
Aid Station #1 (10.6 miles) – Rolling terrain with some deep sand, rolling hills and the occasional rock garden.
Aid #2 (24.3 miles) - Right out of the aid station you'll begin a steep, loose climb.
to Westwater Aid Station/ turnaround (30.3 miles - This section starts with a short (maybe rideable) climb where you'll gain over 400′ in just over a half mile. After a short easy section to catch your breath you'll begin the technical ledge-y descent off the mesa.
Westwater/turnaround to Zion Curtain
Aid Station #3 (36.3 miles) – The ledge-y, technical ascent will give way to to a nice flowy trail right before you drop down the steep half mile descent to the Zion Curtain
aid station. You'll need to keep your bike under control as there may be riders coming up that same section of trail.
Aid Station #4 (50 miles) – You'll ride this loop in reverse with the flat section at the start. This is a strenuous section with a steep treacherous section (most will have to dismount) at the start of the descent to end the loop.
Note that this route travels mostly through the desert. Because of this, it's hot in the summer, dusty, and dry. This route uses a few roads, and quite a bit of trails. No matter where you ride, rocks abound. Lots of sky. This trail has all the crucial elements you've come to expect: elbow room, some mondo pitfalls to avoid, human conflict, and potential heroics, terrific shock value, and high drama 'round every corner.
Shout out to Michael DiGregorio for his assistance with this description. Damn I miss early and mid-90s Bike Magazine...