Duragrouch

From another of my posts on a different thread:

I have changed from square taper BB, to the "hollowtech II style", which has a hollow tube axle bonded to the right crank arm. The BB bearings do not go deep inside the BB frame shell, but are "external" (I think Phil Wood co calls this "outboard"), fitting between the shell and the crank arms. I REALLY like this system; The ball bearings inside are larger or more of them, it feels smoother, and they are mounted closer to the crank arms, reducing bending moment (and radial loading) on the tube and bearings. I can also take the crank completely off with only an allen wrench. The external bearings require a special wrench, I bought a 4-way one so am set for most styles of these. I opted for "ISO External" bearing standard, it is very common and not proprietary. One person on here, mountain biker, said he feels external bearings go bad quicker, and I said that may be true in his riding environment, due to a) larger seals, b) seal right against the crankarm, so dirt between could grind at seal, c) internal cartridge style BB, seals are further from the crank arms. But my external has worn much better than the previous cartridge internal (street use only, dry only), and adjusting to remove slack in the bearings over time is a 2 minute operation, a big plus for someone like me that does a lot of mileage, and keeping the slack out, proper preload, greatly prolongs bearing life in terms of loading on the balls, and no BB axle radial movement to stretch the seals. With a cartridge internal BB, there is no way to adjust to take out bearing slack when it shows up, and then deterioration accelerates. With external, I stay on top of it, the moment I feel any slack while laterally wiggling the crank arms, I immediately readjust, takes 2 minutes, a touch longer if I take that opportunity to clean out any dirt from between the crank arms and bearings.