DaveS wrote:
FWIW, ISIS has the same spindle diameter as octalink, so the same bearing design restrictions apply to both.
That's what is commonly thought to be true in the industry. And probably why ISIS developers thought it wouldn't be an issue.
ISIS and Shimano are very close to the same OD....On the exposed part of the spindle.
ISIS is basically sealed cartridges(using both inner and outer races) pressed into a sleeve with a straight gauge spindle slid through the center.
The Shimano is completely different. It's commonly thought that it uses sealed cartidge bearings. When if fact it doesn't. As well, it doesn't even use a full compliment. There are only 7 bearings per row. The spindle starts at just under 22mm(the same as ISIS) but once you pass the first seal Shimano steps down to under 18.5. Get the 2nd seal and ball retainers out and you see that at the bearings, the spindle is actually a channel cup at only about 14mm....Basically a groove is cut into the spindle so that the balls can ride directly on the spindle. The end result is that the Shimano ends up with a bearing that is huge in comparison to the ISIS.