The Mavic Crossmax SL Ultimate 30 wheel runs a 30mm internal rim width, wider than its 25mm sibling, for added tire volume and control when the trail turns technical. Adaptive Layup carbon pulls material from around each spoke hole to cut weight without giving up stiffness, and double-butted, two-cross spokes keep power transfer efficient while adding just enough give to soak up trail chatter. What Our Gearhead(R) Experts Are Saying:"For a fast, hardpacked course I build the 25 up front and the 30 in back, keeping the front end quick through corners while the rear holds traction under power. On a loose or rocky course I spec both wheels at 30, since the extra tire volume front and rear keeps the bike tracking straight under braking."