“Larger diameter cartridge bearings will always spin with more friction than a similarly-constructed smaller diameter bearing.”
i’m not sure i buy that, unless you’re talking about an unloaded crank.
I agree. The main force at work on a bottom bracket is torsional load, not friction from heat. I actually think that under load, an external BB may have the *potential *to have less drag.
Regardless, the fact that no one has been able to quantify the difference makes me think that it’s infinitesimally small. Bike shop employees spinning a crank in a stand isn’t much of a test. For all those who claim to ‘feel’ their $200.00 ceramic bottom brackets while riding (or anyone else), I’d suggest this simple test:take the chain off of the crankset, put your bike on the trainer, and get on and pedal. Do you feel any resistance holding you back?
I do like the external bottom brackets, though. It’s way easier to remove the crank for cleaning–and a clean drive train IS faster.