hm, get a wider bottom bracket, shimanos are cheap and are amazing, most of my friends run them and none of us have had a problem yet. i also need to get a wider bottom bracket because its not wide enough, i have about 1mm at max chainring clearance on my echo control and as soon as the bearings start to go it will rub almost instantly. to be honest do what moza says and go single speed then you can adjust the chain to be inline with the chain ring then tension it so it wont fall off.