i have a 70s peugeot i converted to fixed recently, and i have an almost straight chainline. its not bad that my chain falls off a lot, just maybe like once every other week so its not terrible, but its less than ideal. do i have to get a new bottom bracket with a smaller spindle? and since my bike is so old i need to get a french BB. or is there anything else i can do that may help? and if i do need to get a new BB, i have only found french ones in spindle lengths of 107 and 113 by velo orange. any idea which i would need? thanks