Originally Posted by
tiger1964
... As I had a few years back installed a sealed-bearing bottom bracket, (1) a little frustrating that it did not last long, and...
EDIT: Oh heck, just realized that with Italian threading, the following does not apply, you can't get a hollow spindle crank in Italian (I think). But good general info:
Yes, that drove me nuts too. Good quality cartridge too, dry weather road riding only.
Generally, internal BB cartridges are superior to old-style cup and cone with bearing cages or loose balls. EXCEPT, once the cartridge starts to loosen up the slightest bit, wear accelerates, because the load is only going into 2-3 balls per side. With proper (original) bearing preload, the rider load goes into almost 180 degrees (half) of the bearings per side. With a cartridge, you cannot readjust the bearing preload to correct this. And you need to, because, while the balls or rollers are quite smooth, the inner and outer races have very fine grinding marks, and during break-in, the surfaces get burnished smooth, the grinding marks disappear, but that also opens up slack in the bearing.
And this is the most important reason why I love (newer) 2-piece hollow-spindle cranks with external bearings (Hollowtech 2 style); Once the bearings burnish in after a couple months of riding, the preload can be restored in 2 minutes by just loosening the left crank arm clamp, retorque the end preload cap, and retorquing the crank clamp bolts. And then, the bearings will often go YEARS without need for readjustment. It's that initial burnish-in that is most the issue. Besides preload, other benefits of this design are:
- external bearings allow larger or more balls, so more durable and smoother feel
- external bearings are farther apart, reducing their load
- external bearings allow a larger diameter spindle that is both stiffer, and lighter
- crank can be removed, even in the field, with no crank pulling tool, using only an allen wrench
Most of these newer cranks are in 4 bolt asymmetrical or symmetrical chainring pattern, and some where you need matching brand chainrings to look right. HOWEVER, if you look hard, you can find hollow spindle cranks in classic 5-bolt spiders on standard bolt circle diameters like 130mm, 110mm, etc.
Any time I need to replace the BB bearings, I upgrade to a hollow spindle crank, if I can find one in classic spider design with bearings included for a good price. The external bearings take a special wrench, I bought a 4-way one so can do many different spline patterns, but my crank uses "ISO External" bearings, which I think is the most common pattern.