The_Mickstar

As far as dependability, durability, etc., what's your choice for road bike use & why?

Do any of these systems have noteworthy weaknesses?

Thanks.

Steve

operator

Square taper. Huge variety of cranks to use, many different lengths and available nearly everywhere.

bikemeister

GREAT QUESTION! I've been thinking about it myself lately. I'm a fan of the square taper, for reasons already stated.
I've heard that the different manufacturers made the taper of their components slightly different, so folks couldn't mix and match parts. A Shimano square BB, for example, wouldn't interface perfect with a SunTour or Stronglight crank. Does anyone know if that is fact?

BCRider

Square taper has been around for so long there's lots of options. I also noticed that the Shimano Hollowteck cranks seem stiffer and no heavier so I tend to like them.

I think Octalink or Isis is a little more rigid and lighter all at the same time but the splines need to be surgically clean before greasing and assembly so there's a certain fuss factor there.

The new external BB setups with the BB axle integrated into the drive side crank are amazingly rigid and much lighter than any of the previous methods. I'm not fussy about the dirt/moisture seal arrangements I've seen on my first two such setups. They are light duty and apparently fragile. The one lightly used unit I got has a seal that is trashed just from some light use or the unmounting efforts. I can see how this could easily happen since it's such a thin lipped seal. I'm waiting on a replacement.

For durability, simplicity and longevity I'd have to go with an LX level sealed BB and something like Deore or LX or the road equivalent hollowtech square taper setup. I've got two such setups on my regular commuters and they've seen thousands of kilometers of winter rain and grit and spin as good as new these 8 to 10 years on.

HillRider

There are two square taper configurations. Both use a 4° included taper angle but ISO spindles (Campy, other European cranks and a few Suguino and Sun Tour crank models) start out slightly smaller at the ends than JIS (Shimano and most other Japanese cranks). The two tapers really aren't interchangable but a lot of riders do it anyway and most are successful as the dimentional differences are rather small.

Square tapers have been around for many years and are a well proven design. Good quality square taper cup-and-cone bottom brackets have a long service life if installed and maintained properly. Cartridge bottom brackets require no maintainance and good ones last for years.

ISIS and Octalink bottom brackets are similar but not interchangable designs and all of them are cartridge types. Shimano's Octalink bottom brackets have a good reputation for durability. ISIS bb's, since it is a public domain design, vary wildly in quality. Poor ones are REALLY poor. Good ones seem to last adequately. Both are somewhat stiffer than most square taper spindles and can be slightly lighter.

My personal preference is for a good cartridge square taper that matches the crank or an Octalink for 9-speed era Shimano cranks. Both are good choices. I've never owned an ISIS bb and crank and see no reason to change that.

Ex Pres 

Octalink/ISIS uses a smaller ball bearing size than square taper and wear out faster, hence the very quick change away from this standard to the current EXO standard.

HillRider

Theoretically, yes the smaller bearing aren't as durable. Realistically, Shimano's Octalink bottom brackets have proven very durable. As mentioned, a lot of ISIS bottom brackets have been fragile.

Soil_Sampler

mine have been very reliable so far.
some isis are extremely durable.