Interesting read. Thanks for posting.
In my quiver, I have an extreme range of BB drop from 50mm to 80mm.
For me the biggest and most obvious difference is pedal strike. The 50mm drop will never have pedal strike (unless I hit something), I can ride on a 45 degree incline with no strike. The 80mm drop threw me off the road at 30mph when the pedal hit the road turning left. When your pedal hits the ground, your rear wheel is lifted off the ground and then dropped back down. Not a pretty site.
I don’t know if I can really attribute much stability to drop. The wheels are huge gyroscopes and I can easily ride with “no hands” on either bike. A mountain bike with “long, low, slack” geometry is easier to ride fast down hill, but I’m thinking that is more of a head tube angle thing (and rider position on the bike). Going down hill standing tall, sitting down, or using a dropper post makes a difference. But does moving the BB 10mm? Kinda, a little maybe….? Clearly a couple of inches (i.e. dropper post) makes a difference for hard mountain biking.
Interesting comments about its effect on the frame. Higher bottom bracket allows for shorter chain stays (and presumable a more responsive bike). One can of course make longer chain stays without dropping the bottom bracket.
Bottom bracket is just a part of the picture though. Typically a low bottom bracket (these days) is included with longer wheelbase and slacker head tube angle. To me, these make the bike feel sluggish and less responsive. Of course this is a good thing if you like bombing down hill, or take trips that are so long that you are totally wiped out at the end of the ride.
I agree with the author, that on most bikes, a 70mm drop is a good target for a responsive bike. That is my target.