The route begins in the glacially carved surroundings of Banff National Park in the southern Canadian Rockies. It passes through the heavily forested mountains of Montana and Idaho, meanders down through the Tetons into the barren high desert lands of Wyoming's Great Divide Basin, ascends again up and over several 10,000 to 12,000 foot passes in Colorado, and switchbacks through rugged mountainous sections of New Mexico before finally dropping into the Chihuahuan Desert. The majority of New Mexico is forested, not desert. The route's highest altitude is around 11,910 feet (3,600 m) above sea level at Indiana Pass in Colorado. The first half of the Canada segment, Montana, and New Mexico are generally considered to be the most rugged and challenging sections, but pockets of difficulty exist throughout. Violent thunderstorms can happen at any time on the route and are the biggest impediment to progress, as they often render the riding surface impassable.
The fastest time to complete the entire GDMBR is 17 days, 21 hours, and 10 minutes clocked by Matthew Lee in 2007. This effort was ridden in conjunction with the Great Divide Race (GDR: a race that covers the 2,493-mile U.S. segment) and as a pilot run of Tour Divide (TD: full-route divide racing). John Nobile currently holds the GDR course record with a 2008 time of 15 days 1 hour and 26 minutes. The idea of racing the GDMBR is the inspiration of endurance racing legend John Stamstad, who successfully completed the first ever individual time trial (ITT) on the US route segment in 1999. The summer of 2008 marked the official advent of the second competitive event on the route. Tour Divide races under the same self-support rules as the GDR and also travels southward but it begins from the route's northern terminus of Banff, Alberta. The two events begin ~ a week apart from each other in mid-June; TD starting the second Friday in June and GDR the third. The times-to-finish in these competitions are particularly impressive as they are completed under a self-support, solo cycling rule format that prohibits any outside assistance on route.
Physically, the route poses many challenges. Cardiovascular fitness is key. Most of the route is in the mountains or the high desert above 6,000 feet, and it reaches altitudes as high as 11,900 feet above sea level. Approximately 85 to 90 percent of the route is over dirt or gravel surfaces. A rider may lose 10 percent of his or her body weight during the ride. Carbohydrate, protein, fat, fluid, and salt intake are critical for stamina and health. A rider will pass through free range cattle lands and be exposed to water born parasites and viruses, not unlike traveling through an undeveloped country.
Endurance is more important than speed. In some sections it is impossible to go fast, and certain rough downhill sections can be as challenging to ride as many of the long uphill portions. Prevailing winds tend to blow from the southwest, so if riding north to south riders will experience their share of strong headwinds. They may also be exposed to thunderstorms, hail, snow squalls, and temperatures ranging from below freezing to above 100 degrees F. Temperatures can fluctuate fifty degrees or more within a single 24-hour period.
Overall, the route is moderately difficult. Some of the most challenging portions can be the relatively flat, open basins, where headwinds often blow the strongest. And, counterintuitively, some downhill sections can be almost as much work to ride as the uphills, due to headwinds or poor road quality. Montana is arguably the most technically challenging state, while New Mexico dishes up the roughest environmental conditions.
Many towns along the route are very tiny with a limited selection of groceries and goods. And relatively few bike shops are found on the route. Research what is available in the way of local bike shops before setting out. A possible way to ensure you will have the fresh parts and supplies you'll need is to mail them to local post offices to: USPS General Delivery, c/o your name. There are time limits on how long post offices will hold mail, so contact each one for specific information.
Obtaining adequate potable water can be challenging on portions of the route (especially the Great Divide Basin in Wyoming and portions of New Mexico), so riders must have enough carrying capacity for several days' worth. There are also several multi-day stretches of the route (depending on the distance ridden per day) where no services of any kind are available, so riders must be prepared to be completely self-sufficient.
A water filter or chemical means of sanitizing river or creek water is essential. A cell phone can be carried, although it won't work in many remote areas. Insect repellent will be needed in some areas at certain times of the year. Horse flies can be as big of a problem as mosquitoes, and they will bite through clothing. A thoroughly waterproof tent should be packed along. A good cycling odometer is a must for successful navigation.
Some riders find a mapping GPS device useful, as it can provide additional peace of mind. The route, however, is successfully ridden many times each year without the benefit of a GPS. GPS routes and waypoints are available from Adventure Cycling and from other enthusiast websites.
Weight is everything. "The real luxury is enjoying the ride, not carrying luxuries around." ( Trek4fun.com)