How many miles does it take to break a new belt in properly? So my thought is during these first agonizing 100 miles to break in the new 50th LTX I would break in a couple of new belts also. Gonna run the 8Jp belts. Run the first one for 50 miles and then put on another new belt for the other 50 miles. Not that this matters but I have the orange secondary spring, HD rollers and Dalton primary spring from TD and a belt adjuster as well. Is 50 miles @ really slow speeds enough for a good break-in?