Originally Posted by
pasopia
Excuse my ignorance, what makes an external BB less tool dependent? I've always used square tapered bbs, except on my mountain bike and I haven't had to mess with it yet. I don't usually carry a bb tool when touring
You have to have a 14mm socket or an 8mm allen wrench and some serious torque to properly tighten a square taper crank (or ISIS for that matter). You'll likely not be able to remove the crank if you need to, either.
External bottom bracket cranks like the Shimano XT require a 5 mm allen to tighten the nondrive side onto the spindle. If you need to remove the crank to service the bearings, it's a simple procedure. Look at the left side crank in the picture below.
Loosen the bolts and the crank comes right out. It's very simple and quite elegant.