I'll take mine when it's going to be a long way, like 50 miles, between controls or water sources and it's going to be hot. A lot of climbing is a given. Two liter bottles plus a 70 oz. Camelbak is about right for those conditions. I just wear it on my back, empty, when I don't need it, 'cause I don't have a rack when I'm randoing on my single. We don't do crazy stuff like that on the tandem.