HomeClimbingBosch Gnarley

Bosch Gnarley: Classic Slab Climbing in Sierra Eastside

Mammoth Lakes, California United States
slab
trad
single-pitch
small gear
granite
technical crux
Mammoth Lakes
Length: 170 ft
Type: Trad
Stars
Pitches
1
Location
Bosch Gnarley
Aspect
South Facing

Overview

"Bosch Gnarley is a single-pitch trad slab in the heart of the Sierra Eastside offering 170 feet of engaging footwork and subtle protection. A technical crux after the fourth bolt challenges your sequence on solid granite, making it a must-do for slab enthusiasts visiting Mammoth Lakes."

Bosch Gnarley: Classic Slab Climbing in Sierra Eastside

Bosch Gnarley offers climbers a straightforward yet satisfying slab climb on solid, textured rock within California’s Mammoth Lakes area. This single-pitch trad route stretches roughly 170 feet along a clean vertical face that challenges your footwork and balance more than brute strength. As you ascend, the rock feels alive beneath your hands, its coarse surface offering subtle friction that demands precise placements. Early moves are mellow and rhythmic, easing you into the climb’s flow before the crux appears just after the fourth bolt—a technical section where careful sequence and steady nerves are key.

The protection is a blend of fixed bolts and traditional gear, making this route approachable yet engaging for those comfortable with light trad placements. You’ll clip seven bolts spaced evenly along the line, but prepare to place small pro in a horizontal crack beyond the third bolt—bring gear sized between 1/2" and 1" for these tricky placements. This mix keeps your focus sharp and offers a welcome change in movement as the route shifts from bolt-protected to a more serious gear section.

Upon topping out, the climb opens onto a ledge gathering place shared by nearby lines like Prodigal Sun, Burnin’ and Lootin’, and Rat in the Kitchen, setting the stage for a communal feel among climbers. The approach to Trenchtown Rock is manageable with well-marked trails, making Bosch Gnarley accessible yet still feeling tucked away in the vast Sierra Eastside wilderness. Expect crisp mountain air, mixed pine and granite surrounds, and the quiet companionship of this high-altitude climbing spot.

The Sierra Eastside’s unique blend of dry, textured granite and moderate traffic awards climbers a blend of solitude and quality movement. Best timed in spring through fall, early morning ascents provide favorable temps and soft light on the slab, while midday sun can warm the rock but may also bring increased glare. Be mindful of weather shifts, as monsoon season can bring sudden storms and slick conditions.

Geared with a light rack focused on small cams and stoppers for the horizontal crack and its bolts, Bosch Gnarley demands attention to gear placement and foot precision. The straightforward approach and clear descent route make this an excellent choice for climbers looking to stretch their trad skills in a stunning alpine setting without committing to long multi-pitch routes. Whether you’re aiming for a confident send or a refined slab session, Bosch Gnarley offers a balanced adventure framed by the high Sierra’s grand natural backdrop.

Climber Safety

The horizontal crack after bolt three requires secure placements of small gear; neglecting this can increase fall risk. Granite can become slick in wet weather, so avoid climbing during or immediately after rainfall. The anchors lead to common descent paths, but pay attention to footing on the walk-off to prevent slips.

Route Details

TypeTrad
Pitches1
Length170 feet

Local Tips

Start early to catch cooler granite and avoid glare during midday.

Carry a small rack focusing on cams between 1/2" and 1" for the horizontal crack protection.

Approach via well-marked trails leading to Trenchtown Rock; allow about 20 minutes.

Descend by walking off to the right side of the anchors following the common routes.

Route Rating

Difficulty
5.10a
Quality
Consensus:At 5.10a, Bosch Gnarley is well-graded with a crux that demands precise footwork and confident gear placement. The rating feels true to the technical demands of slab climbing, requiring balance and delicate moves rather than power. Climbers familiar with local Mammoth Lakes slab routes like Prodigal Sun will find this climb aligns well with that style.

Gear Requirements

The route features 7 bolts complemented by a critical small gear placement in a horizontal crack after the third bolt. Climbing with a rack including cams and stoppers sized between 1/2" and 1" is recommended to secure this section safely.

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Tags

slab
trad
single-pitch
small gear
granite
technical crux
Mammoth Lakes