<p>First, I don’t think the OP stated that the bikes were mountain bikes, they could be some of the newer upright flat bar "comfort"bikes built with road frames and components. Even if they are mountain bikes, there’s a world of difference between the “beating” mountain bike frames, wheels and forks are designed to take and the stresses small parts like derailleurs (with their long pulley arms in the rear and parrallelagram cages in the front), rear d</p>