Super Flag, Gross Reservoir, and Coal Creek loop — Gravel

This challenging gravel cycling loop usually takes around 3 hours and 37 minutes to complete. However, your actual time may vary depending on your fitness level and how often you stop to enjoy the views.

The route features a diverse terrain. You'll encounter steep paved sections on Flagstaff Road, with grades averaging 8.2% and some reaching 20%. Around Gross Reservoir, Gross Dam Road is mostly smooth, hard-packed gravel with challenging grades of 12-15%. The Coal Creek portion likely includes regional crushed gravel trails. A gravel bike is highly recommended due to the mixed surfaces.

No, this loop is consistently rated as a 'difficult' road ride, requiring 'very good fitness'. With a substantial elevation gain of 1,260 meters (approximately 4,134 feet) and steep grades on both paved and gravel sections, it is not recommended for beginners.

You'll be treated to stunning scenery throughout. The climb up Flagstaff Road Scenic Drive offers expansive views over Boulder. You'll also pass the Super Flagstaff Summit, and ride alongside the beautiful Gross Reservoir, with marked scenic overlooks providing amazing mountain vistas.

Parking options exist around the Boulder area. For Gross Reservoir access, the North Shore picnic area and parking lot remain open. Be sure to check local regulations and signage for specific parking areas and any potential fees or restrictions, especially given the ongoing Gross Reservoir Expansion Project.

The best time to cycle this route is typically from late spring through early fall (May to October) when the weather is milder and the roads are clear of snow and ice. Always check current weather and road conditions, especially for higher elevation sections and gravel roads, as conditions can change rapidly.

This route passes through Boulder Open Space and Mountain Parks (OSMP) land. While there are generally no entrance fees for OSMP trails, some specific areas or parking lots may require permits or fees. Always check the official Boulder County website for the most up-to-date information on regulations and any required permits, especially concerning the Gross Reservoir area due to ongoing projects.

This route is primarily a gravel cycling loop on roads and trails. While dogs are generally allowed on many Boulder Open Space and Mountain Parks trails, specific regulations regarding leashes and access can vary. Given the nature of this challenging cycling route, it might not be ideal for dogs. Always check current OSMP regulations for specific trail segments you plan to traverse, especially around Gross Reservoir and Coal Creek.

Yes, the route incorporates sections of various paths. You'll find yourself on parts of the Broadway Path, B360, Marshall Mesa, Josie Heath Trail, and the Flagstaff Trail, among others, as you navigate this extensive loop.

Given the route's difficulty and remote sections, you should bring plenty of water, nutrition, a repair kit (including spare tubes/patch kit), a pump, and appropriate clothing for changing weather conditions. A gravel bike with suitable tires is highly recommended. Be prepared for self-sufficiency as services are limited along much of the route.

Yes, as parts of this route traverse Boulder Open Space and Mountain Parks (OSMP), cyclists must adhere to OSMP regulations. This includes staying on designated trails, respecting wildlife, and being aware of potential seasonal closures or restrictions. The Gross Reservoir Expansion Project has also impacted public access in some areas, so always check bouldercounty.gov for current information on access and any construction-related impacts.