time to resurrect this thread since i am having this problem way too often. actually i did a coaster brake build for a friend and his back wheel is frequently jamming, especially on turns he says. the frame spacing is 123ish and i dished and spaced the back wheel nicely. chainline is good. i've had to fix his back wheel four times! i even rebuilt the damn wheel using sapim race spokes and a rigida sputnik rim b/c i am at my wits end!

the only thing i can think now is that either there is an uneven force on the left side (with the brake arm) or the frame alignment is off. since the physics of the whole thing is beyond me, i am lost. anyone else care to chime in and help out?

some facts:

rear hub is velosteel. brake arm is not directly below the chainstay but offset to the right, fastened using a sturdy velo-orange p-clamp.
nuts are track style with serrated washers built in. real tight!
lock nuts are also serrated.
left side has an attachment for trailer between nut and frame. image below



thanks!