Originally Posted by
Winfried
Am I correct in understanding that MTBs usually use a 73mm BB shell while road bikes usually come with 68mm shells, which is why hollowtech BBs sometimes/often come with 5mm worth of spacers?
Yes. for the most part. But they do specify a 70mm shell also for road bike bb's also.
Not sure what you didn't understand, but the spacers per the DM go on both sides of the BB. At least the few for mtn bikes that I've looked at do. Some people alter their chain line ever so slightly by putting them all on one side of their bb shell if it's smaller than 73mm which wouldn't get spacers installed.