My friend has a mountain bike that is used on the road and trails, he pulls a trailer behind the bike that weighs about 90 pounds loaded, and the back tire wears out fast. What tire do you recommend that would hold up to that kind of use. He rides at least 20-30 daily. The bike is has a 21 inch frame and he is 6’1. So he mostly rides on the roads but prefers the mountain bike. Appreciate your help.