They do NOT block out exterior noise very well. I would not recommend these for riding a bike. Look for something that goes in the ear a little more. Despite the "in ear" part of these headphones, they don't actually go in your ear very far at all.
I ride an Ultra. These are far better Than any earbuds I've bought before. But they aren't noise canceling so they still haven't eliminated the surrounding sound. Better sound but not quite worth the $100+. The quality of the cord is really lousy. Mine got a tear within two weeks.