WALNUT CREEK, CALIFORNIA – On Sunday, October 5, 2025, hundreds of East Bay riders will point their front wheels up Mount Diablo for the 42nd Mt. Diablo Challenge—an 11.2-mile, timed grind from the Athenian School to the 3,849-foot summit with 3,249 feet of climbing.
It’s the one day each year the mountain goes car-free for a mass ascent.
What it is
Organized by the Valley Spokesmen Bicycle Club, the Diablo Challenge is an individually timed hill climb run in waves. The course follows South Gate Rd. → Summit Rd. → summit, with a post-ride BBQ, awards and live music back at the venue.
When & where
- Packet pickup: Sat, Oct 4, 2–6 p.m. at Trek Alamo (180 Alamo Plaza).
- Event-day check-in & parking: Sun, Oct 5, from 7:00 a.m. at Monte Vista High School (3131 Stone Valley Rd., Danville). Riders then pedal ~2.9 miles to the Athenian School start. First wave rolls 8:15 a.m.; subsequent waves at 3-minute intervals. Course closes 12:15 p.m.
Road closures (plan ahead)
California State Parks says vehicle access to North Gate, South Gate and Summit Roads will be closed 8 a.m.–2 p.m. on Oct 5 for the event. Macedo Ranch and Mitchell Canyon entrances remain open, and all trails/fire roads stay open.
Who can ride?
Pretty much everyone. Allowed bikes include road (single or tandem), mountain, fixed-gear, unicycles and outdoor elliptical bikes. Class 1 & 3 e-bikes may participate but aren’t eligible for prizes or awards. The field is capped at 1,200 riders.
How hard is it?
It’s a sustained climb with bite: 11.2 miles and 3,249 feet up, with long steady grades and a sting in the tail near the summit. (Coaches peg the average gradient around ~5.8% with steep pitches that feel much spicier.)
Spectating & after-party
For safety, no spectators on the roads—access is trail only, and the park roads are car-free during the event. Your best bet is to cheer riders at the post-ride festival at Monte Vista High (food, music, awards). Descents are escorted by lead vehicles; riders must wait at the summit and may not pass the escort.
Register (still open)
Online registration remains live via the event site; T-shirt availability isn’t guaranteed for registrations after Sept 1. The organizers also note early-bird pricing ended Aug 31 and online signups close Sept 29.
Why it matters
Proceeds support cycling safety improvements on Mt. Diablo, and the temporary road closure creates a rare, car-free shot at the summit with hundreds of locals pushing together.
