My bro did the Trans Iowa bile race this weekend. 350 miles in 27 hours! He came in 5th overall! All I can say is wow! I didn't even know bike races like this existed. Sure there's a legendary race in colorado, a 100 mile off road ride, but this was 350 miles! That and he didn't even tell me he was doing it. LOL.
It's hard to explain, but it's sort of like an ultra-marathon for off road bikers. All dirt roads, gravel, sand, two track, whatever's there. On mountain bike, cyclocross... some people even do it single speed.
It's hard to imagine a 350 mile ride. I mean, I try to ride 80+ miles once a week, have gone over 100 a couple times, most people would agree that's fairly epic riding. Centuries (100 mile rides) are sort of the norm for long distance riding, sort of the marathon (26 miles) being the norm for long distance running. There are also 24 hour races, whatever distance you can do in 24 hours, also common, but those are on closed circuits, you just ride on a predefined loop over and over. This new 300 miler is not a repeat loop. It's a 300+ mile course.
I see now there is a Red Assinbone 300 near Winnipeg in Manitoba Canada. I'm not sure if this is a new trend in biking, but I like it.