Originally Posted by
unterhausen
I would be inclined to worry more about bb height on a mtb, but it doesn't seem like there is any safe bb height on the trails around here. I'm sure there is some height that is the difference between a lot of rock strikes and a reasonable number of rock strikes
Thing is a 2cm difference in BB drop is considered a lot in frame design terms but doesn't feel like a lot from the point of view of random rocks on the trail.
I built a long low slack 29er hardtail and went with a 70mm drop. This is more than most bikes out there but there's plenty of clearance because people run such big tyres these days. Also the guy it was for rides without a dropper post.