ISIS Bottom Bracket....

[mtflycaster]

Maybe this has been discussed before. If so, my apologies.

I'm wondering what motivated the move from square taper to ISIS bottom brackets. Primarily a cost savings on the part of manufacturers, or better performance? Lighter? Stiffer? Other issues?

Some ISIS systems seem to have had problems...creaking, loosening, etc.

I've never had a problem with square taper, and feel it may be a more robust system for long bike tours in remote places. Easier maintenance and replacement, for example.

Comments?

[Bradford]

I’ve had both tapered and Octalink, but not Isis. I think it is easier to remove a splined crank than a tapered crank.

I’ve had trouble getting tapered cranks off twice in my life, probably because I over tightened them. I take one of my cranks off my coupled tandem at least once a year when I travel with it (to fit it in the box) and the crank comes off without any problem, even when I break down the bike after the tour when I’m out of my shop and don’t have access to all of my tools.

Performance wise, I doubt there any difference either way on the bike, although I’m sure there are claims for better performance on both sides. Maybe the advantage is only for idiots who over tighten cranks or don’t know how to get one off, but it is still easier to get off. If I were starting from scratch, I’d go with splined; if I already had the bottom bracket and crank, I’d go with tapered.

[gdw]

Splined bottom brackets are supposed to be stiffer and allow for easier removal and installation of the crankarms. I can't tell any difference in the performance but agree that they are easier to remove. The drawback to splined systems seems to be that they don't last as long as tapered bottom brackets and can damage the crankarms if the person installing them doesn't seat them properly before tightening the bolts. I don't know if they wear out prematurely because of poor quality bearings or bad design but they are already starting to be phased out by Shimano and their competitors. I'm glad Campy chose not to join in on the fun and stayed with the tried and true square taper.

[Dave]

ISIS is significantly different than octalink. You can't screw up the alignment of the splines. The crank wouldn't even start to go on the spindle if it was out of alignment, so in effect, it's self aligning. ISIS is a tapered spline, so it does fit tighter as the crank bolt is tightened. I've been using ISIS for the last two season with no problem at all. With ISIS, the spindle can be greased or Ti prepped. Removing an ISIS crank should never be a problem due to corrosion.

The idea behind ISIS was to create a large diameter hollow spindle that would equal or exceed the stiffness of the shimano design. Unlike shimano's design, it's not patented and free for anyone to use.

I chose FSA ISIS cranks becasue Campy doesn't offer a 53/39/30 or 53/39/28 triple that I can get from FSA.

Most of the bearing problems came from early models with inadequate seals used on mountain bikes. The mud and after use washings led to early failure. FSA has made even more improvements for 2005, includng the introduction of outboard bearing ISIS BBs.

http://www.fullspeedahead.com/fly.aspx?layout=product&taxid=29&pid=120

Supposedly the outboard bearing model won't work with my road triple, but I can't see why, other than a possible interference with the mounting tabs for the little ring. For some reason these tabs are much longer than needed and could easily be trimmed it looks to me.

If I was buying a new crank, I'd consider the new FSA integrated crank.
http://www.fullspeedahead.com/fly.aspx?layout=product&taxid=21