What is the benefit? I know that the DuraAce OctaLink is NJS approved too. Please let me know what the benefit of each is....thanks!
a.s.

I think one of the main ones is that Octalink can be removed/remounted many times with little wear. Square taper swedges out a little bit every time. Many cycles may lead to poor fit.

So octalink is a bit more durable? DO they make sealed Octalink BBs?
a.s.

Both Octalink and square taper BB are fine. I like Square taper because there is a large selection to choose from. Wear isn't really an issue.... how may times to you need to take your crank arms on and off?

Token makes some excellent square taper bottom brackets if you are in the market. I'm running one of their Ti spindle/carbon shell campy ones right now on my training bike.

Yes they make sealed octalinks. Both systems work well. If you are asking then I am assuming that you are in the market for a crank - otherwise you would only have one choice of BB. I would recommend that you make your choice based on the crank. Consider an external bearing BB/cup design as well.

Square taper uses a 17mm spindle, Octalink and ISIS use 22mm, external bearing (new Shimano) is 24mm (spaced far apart). The spindle stiffness increases exponentially with diameter so Octalink is significantly stiffer than square taper (less chain rub on the front derailleur).

One good thing about square taper is that the spindle is small so there is room for fairly large bearings inside the bottom bracket shell. Some early ISIS bottom bracket’s had problems since the bearings were small but Shimano BB’s have been bullet proof from the start (except for Dura Ace which is not sealed and requires frequent maintenance or the internals will corrode).

In my opinion the new external bearing Shimano cranks are superior to everything else. The spindle is stiffest of the lot, the bearings are spaced wide so they support the spindle well, and the bearings are large for long life. No downside I can think of.

I like the idea of avoiding tapered spindles. However, the left arm (175mm) opposite the rings on the road crank (Ultegra) was bulky; I hit my heel on it. Never happened before. And, it doesn't happen now after I replaced it with a mtb (XT) Octalink left crank arm--it's not as bulky.

Splined BBs are a further perfection of business strategy of changing bicycle standards into proprietary links between various components. In this case it allows the manufacturer to tie the crank and the bottom bracket. Sort of like what Microsoft did with windows and internet explorer.

Splined BB usually are much harder to get seated, for me sometimes it takes several tightenings to get them to stay tight. Other then that I like em. Don't see a big bennefit though. Been using my older Dura Ace loose ball BB for ten years and its smoother.

I have Octalink on my bike and from what I've found more and more manufacturers are moving to ISIS. Not sure what the real difference is, but I had a hard time locating a compact double FSA carbon crankset.

Octalink is proprietary to Shimano so when they moved to external bearing cups then there is nobody left use Octalink. ISIS is a standard so many manufactorers are using it.

I have been using the square taper since I started riding nice road bikes in the early 1970s because up until about the past 10 years, that was all that there was. I still use one. Campy and I never have had any lack of stiffness or chain ring rubbing the front derailure. If that were happening, it would be a function of my bottom bracket shell flexing and a less than rigid frame. With sealed units, you don't or should not have deflection. In the old days, that would happen until I installed my first Stronglight sealed BB and wow was that nice and tight. There is all this discussion about how the newer BBs are stiffer than the old square taper and mechanically that should seem to be the case. But, again, I have no movement or flexing of my crank on my square taper BB. The frame is a Merlin titanium, and not an overly stiff aluminum or carbon fiber.

I have two different bikes; one with Dura Ace 10 speed (integrated 24mm spindle w/outboard bearings) and the other DA 9 w/octalink. The 10 speed frame is more flexable (Foco down tube) vs. a Zona down tube on the 9 speed bike. The 9 speed bikes frame is stiffer in the bottom bracket but it also has more chain rub. I was surprised to experience this when putting the 10 speed bike in service. At any rate, I'm a believer.

Octalink and ISIS are both engineering answers to the use of hollow axles. There are all sorts of reasons to use hollow axles (esp. weight and bearing surface), but square taper design doesn't work with them. Splines are a better answer anyway.

You need to try the new Campy stuff.

and they all all moving away from it.

Bottom brackets are a moving target, they change constantly.

Velonews tested drag on many BB types, found square tapers just as good as some ceramic exo designs.

Interesting. My crank, a Campy Record square taper, is nice and I don't get any chain rub. Not a bit. If I were outfittng the bike today, sure, I'd be most likely with an intergrated set up, new Campy or FSA, or what ever. Until something breaks or wears out, I can't come up with any good reason to abandon square taper.

square rocks...

Though it's true that the spindle stifness increases with diameter, I consider very unlikely that a square taper spindle would flex under a cyclist's wattage. The frame would flex far too much before that.

+100 to that!

When the revolution comes, the Marketers should be the first up against the wall....

With all due respect, I disagree with your estimation that the spindle does not flex. Back in my weight weenie days of mountain biking I replaced the steel square taper BB with a Ti one - 122.5 mm long. The new spindle was significantly lighter but a whole lot more flexible as evidenced by the increase in chain rub the bike experienced. I've experienced the same reduction in chain rub when upgrading a square taper Dura-Ace crank with an Octalink one (not as dramatic a difference as the mountain bike though). FYI, I weigh about 170 lbs and like to sprint over rolling hills instead of downshifting out of the big ring - this is a common situation when chain rub will occur.

Believe it or not, but the spindle does flex. I'm not saying this is a problem per say, just an annoyance for people like me that don't like hearing the noise.

I should have said 'a steel square taper spindle'. Don't know about titanium. Put a 17 mm tempered, hardened steel rod in a vice, leaving 100mm out, or 130 if you wish. Now try to flex it. 170 lb won't do it.

If you do take your cranks off often (bikes travel in cars better that way) then you appreciate the ease with which shimano 9sp dura ace and up comes apart. Also, I think that the axles do flex and more importantly you can make an axle of the same stiffness lighter with a larger diameter hollom design than you can with a smaller diameter solid one.

Okay folks, sophomore engineering.......

The newer hollow spindles are stiffer in torsion, meaning there is less angular wind up as you pedal. However, this wind up is extremely small, and probably won't be felt by the average, or even above average rider. The work energy needed to wind up the shaft is returned to the system at the bottom of the pedal stroke.

Lateral stiffness is a function of the frame, not the spindle diameter or the placement of the bearings. A frame is flexed laterally due to a sideways torque. A crank's "Q" factor will have an effect on this. As before, the energy is returned to the system.

Either way, essentially no energy is lost, so it doesn't make any difference in performance.

There is no need to obsess with "stiffness" in your bottom bracket. Those that do probably obsess with stiffness in other areas.

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