I'm planning to replace my Ultegra triple with an FSA carbon compact (I'm also gonna go DA 10 on everything else).

Anyway, the FSA cranks come in both ISIS and Octalink. Since I'll need a new BB, I was thinking I should go ISIS. I figure that since shimano is going to the integrated spindle with their cranks (DA now, Ultegra in a few months), we're not likely to see any innovative changes to the Octalink splined BB design. Although I'm sure it will be around for a while. On the other hand, I'll bet that FSA will want to innovate their ISIS BBs to keep up with the shimano train -- an version with outboard bearings, stiffer designs, etc.

So, any reason why I shouldn't go with the ISIS BB?

Oh yea, one more thing. FSA advertises their spindle as a 108mm with a 43.5 chainline. Shimano says 109.5mm spindle with 43.5 chainline. What the heck is the "chainline" measuring?

I wouldn't count on the outboard ISIS to be compatible with current ISIS cranks.

Chain line is the distance between the chain rings of a double or the center ring of a triple and the center of your seat tube. Use whatever length BB your crank manufacturer recommends for optimal chain line.

I wouldn't count on the outboard ISIS to be compatible with current ISIS cranks.

Yea. I hear you. I'm not counting on anything. I just want a good BB and the FSA Platnimum Pro and Pro Ti seem nice. At least the Ti seems better than the ultegra.

I'm just thinking that shimano isn't likely to do much with the Octalink in the future. FSA will certainly make improvements to their BBs. And there's a good chance those improvements will be compatible with their current line. Just trying to think long term. Hopefully the cranks and BB will last for many years and not need any changes anyway.

Yea. I hear you. I'm not counting on anything. I just want a good BB and the FSA Platnimum Pro and Pro Ti seem nice. At least the Ti seems better than the ultegra.

I'm just thinking that shimano isn't likely to do much with the Octalink in the future. FSA will certainly make improvements to their BBs. And there's a good chance those improvements will be compatible with their current line. Just trying to think long term. Hopefully the cranks and BB will last for many years and not need any changes anyway.

Seems that Octalink's days are numbered. Not sure how long ISIS will be around but it's nice to support the product with the open standard license.

One nice thing about ISIS is that it's taper shaped so it should wedge on tightly. Should be more durable than a square taper also due to the increased surface area of the splines. Octalink doesn't seem to wedge on quite as tight due to the shape of the splines.

Good luck.

Ed

I have FSA Platinum Pro Ti BB on mtb x 3 years and road bike x1 year. Great BB. Smooth, quiet, stiff, accurately made-chainline and interface. Truvative cranks on mtb and FSA Carbon Compact on road bike. I will buy another for a bike I'm in the process of building.

Seems that Octalink's days are numbered. Not sure how long ISIS will be around but it's nice to support the product with the open standard license.

One nice thing about ISIS is that it's taper shaped so it should wedge on tightly. Should be more durable than a square taper also due to the increased surface area of the splines. Octalink doesn't seem to wedge on quite as tight due to the shape of the splines.

Good luck.

Ed


should be durable ... but why hasn't been? i see so many reports of isis bb's disintegrating quickly(incl. a lot in mtbr/ singlespeed). square tapers, like phil wood like to live forever. i don't get it:
why invent something that doesn't work to replace something that's working fine?

should be durable ... but why hasn't been? i see so many reports of isis bb's disintegrating quickly(incl. a lot in mtbr/ singlespeed). square tapers, like phil wood like to live forever. i don't get it:
why invent something that doesn't work to replace something that's working fine?


...were just that, bottom bracket problems. I don't think this is a result of a flawed ISIS design, rather, it's a problem with some poorly designed bearing seals.

Ed

The reasoning behind the flawed ISIS design is that due to a lack of space the bearings are comparatively small in size. Combine that with a lightweight design/model and reliability suffers regardless of sealing.

The reasoning behind the flawed ISIS design is that due to a lack of space the bearings are comparatively small in size. Combine that with a lightweight design/model and reliability suffers regardless of sealing.
The FSA Platinum Pro Ti is a better design than most of the others. It uses 3 rows of bearings, 1/4". The larger bearings seem to hold up well. Race Face BBs have not faired as well and they have introduced outboard bearings versions, too early to tell how they will do. The ISIS interface standard doesn't cover how to build the bearings/support, so you need to make sure the BB you get has good bearing/seal history, the Platinum Pros do.

I'm about a year into using my FSA Platinum Pro ti bottom bracket, approx 4,000 miles, and no issues as of yet. At first the seals were causing a little drag but they broke in and it spins very smooth with zero play. It's warrantied for two years so if I go another year without any problems I'm happy and if not, it's warrantied. I'm not sure what is considered normal bottom bracket life although I will have over 8,000 miles in two years time.

should be durable ... but why hasn't been? i see so many reports of isis bb's disintegrating quickly(incl. a lot in mtbr/ singlespeed).

I don't know where that's coming from, because my experience is just the opposite: I have the TruVativ ISIS-Drive SL on my CX bike, and no issues in 11 months of almost daily use, (about 75% on-road, 25% off-road).

Maybe some of those MTB'ers are just pounding the crap out of their cranksets/BB's?