The Dingle Peninsula loop trip is about 30 miles (47 km) long and must be driven in a clockwise direction. It’s easy by car, or it’s a demanding four hours by bike—if you don’t stop.

I don't see how we're making it to dinner, I said to my husband, Taylor, as we picked our way up a craggy hill, our backs to the North Atlantic. We were 13 miles into a 43-mile, three-day trek ...