what size hitch ball do I need for a travel trailer

A long travel trailer would either use a 2 inch or a 2-5/16 inch ball. A 2 inch ball can have a capacity up to 8000 lbs, while the capacity of a 2-5/16 inch ball can range between 6,000 and 30,000 lbs. 

Please Note: A bike rack is not to be used on any trailer, fifth wheel or towed vehicle.