I've run 29x2.3 big apples on these for 3k miles and haven't had a problem. Schwalbe recomends not inflating over 40psi on narrow rims I ran 45-50 rear and 30-40 frt. http://www.jensonusa.com/store/produ...+Td17+Rim.aspx the rim width measurment they list is for the outside. I believe the inside is 20mm due to the anti snakebite.