The route we suggest follows old mining roads all the way to the Horseshoe-Peerless saddle. This route is really Class 1 to the summit, but if you use our suggested descent route, it becomes a Class 2 route. Mileage and elevation gain assume a walking start from Leavick. Use of 4WD can shorten the mileage considerably depending on how far up you drive. It's possible to go as high as 13,200 ft. We first climbed Horseshoe in 1986. This may have been our first 13er. Bob Alden, who had completed the 14ers in 1983, was looking for partners to do Horseshoe and prevailed upon us to accompany him on Memorial Day weekend. We took our cross country skiis and enjoyed a long and easily manageable snow descent by following the descent route described below.
Either park at Leavick as described in the trailhead information or drive an additional .75 mile up the road to where a 4WD road turns off on the left at the 11,588 ft. marker on the USGS quad. There's a little bit of parking just before the turnoff and 2WD vehicles can usually make it to that point. Hike on up the 4WD road which changes directions and switchbacks frequently. At 12,600 ft., you'll begin to encounter some mining ruins and farther up toward the saddle, you'll pass by what's left of the Peerless Mine. Once you arrive at the Peerless-Horseshoe saddle, simply turn south and follow the ridge to the summit. You should find a trail leading there. The upper terrain is mostly tundra with some chiprock-scree mix. The road tends to be gravel or some tedious chiprock and small rubble at times. Enjoy the summit view. Watch out for those infamous Tenmile-Mosquito Range winds and return as you came unless you're looking for more adventure.
For a Class 2 descent, head south from the summit until you're past where the broad and prominent east ridge intersects the south ridge. Head on down into the basin below to the ESE on talus, scree and sparse tundra and locate a way to get down to the lower basin at 12,400 ft. If you swing more center in the drainage, you can avoid some brief, rocky couloirs. Once down to 12,400 feet, things level out quite a bit and talus gives way to easier terrain. Head in a generally NNE direction, gradually descending acorss tundra, grass and lower down, passing through some willows. You'll be passing on the east side of and about a half mile down from the two unnamed lakes that sit below the main "horseshoe" basin of the mountain. Cross the creek that drains the northermost of the two lakes and either go uphill just a little or contour to regain the 4WD road used in the morning at about 12,000 ft. Walk on back to wherever you left your vehicle.
Links to other information, routes & trip reports for this peak that may be helpful.