the tektro oryx canti brakes are good value and work well if set up properly. if the straddle cable carrier (
pic) is set too high there won't be enough mechanical advantage to stop without a ham-fisted pull. set the carrier as low as reasonably possible and you'll be totally surprised and happy with them. for me, the straddle cable which came with the oryx (
pic) is either too short or too long (can't remember which, but either way it didn't work satisfactorily). replace with standard straddle cable (
pic)
sheldon brown wrote a detailed article on canti brake geometry (
link) which unfortunately IMO is unnecessarily complicated.