How are ride difficulty ratings determined?

TheRealParisLove

I am pretty new to cycling and am planning to ride my first century on Sept. 30. I'm right on track as far as training goes, but am curious what the difficulty ratings mean.

I plan on riding a 65 mile route this Saturday. http://rideoregonride.com/road-routes/wolf-creek/
The ride is rated as extreme. There is one pretty serious hill right in the middle with a 1000 foot elevation gain over 4 miles. I'm assuming that is why the high difficulty rating when combined with the 65 mile distance. But it is all on paved highway and is used regularly by cyclists, so how hard can that really be?

I guess my question is, are the difficulty ratings exaggerated to scare off folks who aren't in good enough condition to tackle the rides?

Dahamac

For me to judge the ride I would want to know the max grade, average grade, and total feet of elevation gain.

For example: http://ridewithgps.com/trips/746304
That trip has a max grade of 21%, an average grade of 3.2%, and a total elevation gain of 6781 feet in 46.3 miles. One metric I use for rating a ride is the feet of elevation gain per mile, so that ride had 146.46 +ft/mile. That is an extreme route, especially since the heat and humidity were very high.

Another example: http://ridewithgps.com/trips/842387
Max grade, 9.5%, average grade 0.4%, total elev. gain 1828. So 29.25 +ft/mile, that is an easy route as far as climbing but with an average speed of 20.6mph, it was still an extreme ride.

See if you can a little more information about the ride and make sure you know your personal time and speed limits.

Last example: http://ridewithgps.com/trips/909913
Max grade 16%, average grade 1.9%, total elev gain 2847. So 78.21 +ft/mile, which should be a fairly difficult route but because my average speed was so low I really didn't hurt from the ride. If I ride this route by myself or with a group at my normal pace of over 16mph average then it would be a very difficult route.