IIRC the total gain for Sugarloaf is roughly 450 feet, not really huge but not really small. The average grade is something like 8 or 9%. It's not that Sugarloaf itself is that horribly difficult, although the 18% grade section about 1/3 up is usually what causes people to bail. For me it was the idiots who covered 3/4 of the road while walking that made it impossible to get by on the second lap. The people going fast never have to deal with that part. I might have been fine going up it the second time with a 42/25, but instead I was running a 42/23, which is what I used in training going up the hill. I might consider switching to a 39/23 for this year just so it will be a little easier on the steep sections.
The major problem for most people is Buckhill Rd. right before it, with rolling hills that if you time just right (which I now have after riding it about 20 times) are no big deal. But most people don't know how to get over the first big hill on Buckhill Rd. without blowing out your fast-twitch and the 6 hills in a row before Sugarloaf don't give you much chance to clean out the lactic acid. But Buckhill's worst hill is short, averages >15% for most of it, and has the world's worst pavement.
The other problem (other than the heat that everyone has mentioned) is that the winds pick up around 10-11am. Because of the course layout and the constant wind from the East it means you are riding into a gusty 3/4 headwind the whole time. For those 50 minute swimmers and 5 hour riders you'll be 3/4 done with the bike before the wind really hammers you.
The major problem for most people is Buckhill Rd. right before it, with rolling hills that if you time just right (which I now have after riding it about 20 times) are no big deal. But most people don't know how to get over the first big hill on Buckhill Rd. without blowing out your fast-twitch and the 6 hills in a row before Sugarloaf don't give you much chance to clean out the lactic acid. But Buckhill's worst hill is short, averages >15% for most of it, and has the world's worst pavement.
The other problem (other than the heat that everyone has mentioned) is that the winds pick up around 10-11am. Because of the course layout and the constant wind from the East it means you are riding into a gusty 3/4 headwind the whole time. For those 50 minute swimmers and 5 hour riders you'll be 3/4 done with the bike before the wind really hammers you.