For the shuttled downhill, you'll leave a car at the bottom of either DH West or DH East, then park below the top of the mountain. Yes, below. You'll push your bike 500 vertical feet in 1/2 mile to reach the top.

Then you'll plunge downhill over countless ledges for 1700 vertical feet of elevation change. DH West is 5 miles long, DH East is 4.5.

Most of the riding surface is within the Chinle formation, including sandstone, clay, and the awesome Shinarump conglomerate. On the DH East, you'll also hit Carmel formation and white Navajo sandstone.

Because ATVs use this trail, you'll need good loose-rock surfing skills. There are occasional stretches of ATV churn.

An XC bike is fine. I rode my 23-pound race bike, and didn't encounter anything where I wished for more suspension. Bigger tires, maybe.

There are countless ledges and rock ramps. Mostly, you just roll on down. Some riding lines may require a short launch, but alternate riding lines are always available for those who don't want air.

IMHO, if you have to pick only one route, the DH East is more fun and more varied than DH West. So if you have a shuttle vehicle (or can ride a loop), I recommend you descend Red Mountain East. If you're considering the loop ride (see below), DH West is more suited to climbing, but is still a bugger.

If you don't have a shuttle vehicle, you'd probably want to do Red Mountain West. It's four miles on road from the bottom of the DH West back to the starting point. And you can insert the Rojo Trail as part of the ride.

As you descend, there are frequent views south of Steinaker Lake and the valley surrounding Vernal. For the top two miles, the surface is sandy soil interrupted by frequent Shinarump outcrops. Tall longleaf pines surround the trail. At the bottom of DH East, you enter a world of steep white Navajo sandstone. Stay and play a bit. If you get lost, just go downhill anywhere and head toward the highway.

For the Killer XC-out-of-yer-league Loop, park at the bottom of DH West. Ride up 1/2 mile, then pop onto Rojo for 2.5 miles of rockin' rock. Then struggle up the last couple of miles on the Red Mountain DT at 500 vertical per mile. You'll reach the top around mile 6. Continue straight into DH East and enjoy your downhill.

How to get back to the west side after your bike arrives at the flats at the bottom of the East DH? You can either do the ugly road return (10 miles) or catch ATV track at the northwest corner of Steinaker and climb to DH West a mile from the bottom.

Camping: On SR 44, Steinaker is just a mile from the bottom of the eastern DH; Red Fleet is about 6 miles north of Steinaker.
Bathroom: None at the trailheads.
Water: Bring your own.
Bike services, maps, trail conditions:
Altitude Cycle, 580 East Main, Vernal. 435-781-2595

Getting there:  
While driving toward Vernal on US-40, crest the hill and pass the rest area just before town. As you encounter buildings, watch for 2500 West on your left. As of 2010, it's the 3rd street, but it depends on what you count as a street. Turn left on 2500 West.
Shuttle West or parking for Killer Loop:  Keep going north for 8 miles. At N40 32.678 W109 35.275, there's a parking area on your right. The trail is the doubletrack heading north.
Shuttle to Top: Continue north on 2500 West to around mile 13 from US-40. (The road turns to gravel around mile 12.) Spot dirt road on the right at N40 36.447 W109 33.865. Keep right at the fork and park at the end of the road. Start "riding" south on ST at N40 35.896 W109 33.293. The top of both trails is 0.4 miles and 500 vertical feet uphill. Good luck.
Shuttle East:  Go north a couple of miles on 2500 West as above, but turn right at 2500 North (just as it seems you're about to leave town). At the T intersection a mile later, turn left, then veer right. When the road intersects SR 44 two miles from 2500 West, turn left and drive 3.3 miles north. Turn left into a dirt road with an adjacent small parking spot at N40 32.867 W109 31.554. Now take your Top vehicle back to 2500 West and continue north as described above.