Mount Disappointment – Mueller Tunnel loop from Altadena

If you're looking for a truly epic mountain biking challenge in the San Gabriel Mountains, the Mount Disappointment – Mueller Tunnel loop from Altadena delivers. This difficult 34.1-mile (54.8 km) route packs in a massive 6840 feet (2085 metres) of climbing over roughly 5 hours and 51 minutes, making it a serious test for riders with very good fitness and advanced skills.

What to expect on Mount Disappointment – Mueller Tunnel loop from Altadena

The ride unfolds across incredibly diverse and often strenuous terrain. You'll tackle technical singletrack, fire roads, and even some unmaintained paved sections, often contending with loose rock and steep grades. The climb to Mount Disappointment is particularly relentless, with sustained double-digit grades that can average 17% and even hit the high teens. Your reward for this effort? Breathtaking 360-degree panoramic views from the summit, stretching from the Channel Islands to San Jacinto and San Gorgonio, and sweeping across Los Angeles to the ocean. You'll also pass through the historic Mueller Tunnel, a unique highlight of the route, but be prepared for sections where you might need to push your bike due to the steepness and challenging conditions.

Planning your visit

Given the significant elevation gain and technical demands, plan your visit carefully. The route can be especially challenging due to erosion below San Gabriel Peak and loose sediment, particularly if snowfall lingers into spring. Sections like Mount Lowe fire road are closed to public motor vehicles, offering a more focused riding experience. Always check current trail conditions before heading out, especially after rain or snow, and carry plenty of water for this demanding ride.

Trail details

• Distance: 34.1 miles (54.8 km)
• Elevation gain: 6840 feet (2085 metres)
• Difficulty: difficult
• Estimated time: 5 hours and 51 minutes