Plenty of races lay claim to being the hardest/toughest/most arduous/whatever, but as is so often the way, it's the one that doesn't shout about it that has one of the strongest claims.

The Great Divide Race has just started in Montana. The course follows the 2,490 mile Great Divide Mountain Bike Route, a trail that covers the whole of the United States from north to south, traversing Montana, Idaho, Wyoming, Colorado and New Mexico. That's quite a long way, and there's a fair bit of climbing involved too - over 200,000ft. 85% of the route is made up of various species of dirt road, with 14% Tarmac and 1% singletrack.

That's not the best bit, though. The best bit is that the race is a self-supported, solo competition. Which means exactly what it says - competitors are out there on their own, carrying everything they need and restocking from shops on their way. Forget stage races - in the GDR you make your own stages. Or not, as you prefer. As the race notes helpfully point out, "If you average 130+ miles per day you will encounter one or more stores per day."

The history of the GDR goes back to 1999, when legendary endurance racer John Stamstad time-trialled the route in 18 days and five hours. That record stood for five years, until the inaugural Great Divide Race was held in 2004. Winner Mike Curiak completed the course in just 16 days and 57 minutes - an average of just under 6.5mph.

Unlike most races, there's no entry fee and not really an organiser as such. But then, with an unsupported race over a well-established long-distance trail, what would they do? There is a website - www.greatdividerace.com - with advice and race updates gleaned from the riders themselves calling in. It's an inexact science - the starting roster has eight names on it, but four days in the site says, "Others may have started, some of these listed racers may not have started."

What we do know is that a couple of them are having trouble already. Mike Gibney pulled out after one day, while David Nice had his bike stolen while sleeping by the side of the trail. This is all the more bizarre as he's riding a fixed-gear MTB, which we'd have thought would prove fatal to any wandering bicycle thief.

The other racers thought to be competing are Matt Chester, Rudi Nadler (also both on fixed gears - it clearly takes a special breed of lunatic to ride the GDR...), Matthew Lee, Kenny Maldonado, Kevin Montgomery and John Nobile. As far as anyone can tell, Matthew Lee is in the lead at the moment, but there's every chance that we won't really know who's won until they've done so...