ISIS vs Octalink vs square

[drewski]

Originally posted by Mike Demicco
In article <[email protected]>, jim beam <[email protected]> wrote:

> > Octalink is flawed, a poor design.
>
> how so?
>
> octalink has a taper for snug fit and lateral load bearing. the splines only transmit torque.

I don't know what "lateral load bearing" means, but Octalink splines are not tapered to prevent
backlash from developing in the splines, especially if you do not descend with the left foot forward
(do a Google search on the subject). Octalink does have a shoulder that the crank butts up against,
so there is no variability in the chainline if used with the proper length bottom bracket. I suspect
that is one of the main reasons Shimano went to this style of bottom bracket. ISIS does not have
this shoulder.

--
Mike DeMicco <[email protected]> (Remove the REMOVE_THIS from my email address
to reply.)

ISIS drivetrains also seem to creak more than Octalink.

 

[Matt O'Toole]

"Mike DeMicco" <[email protected]> wrote in message
news:[email protected]...

> In article <[email protected]>,

> jim beam <[email protected]> wrote:
>
> > > Octalink is flawed, a poor design.
> >
> > how so?
> >
> > octalink has a taper for snug fit and lateral load bearing. the splines only transmit torque.
>
> I don't know what "lateral load bearing" means, but Octalink splines are not tapered to prevent
> backlash from developing in the splines, especially if you do not descend with the left foot
> forward (do a Google search on the subject). Octalink does have a shoulder that the crank butts up
> against,

Taper or not, there cannot be a press fit with such a shoulder, or with the axle bottoming out
in the hole.

> so there is no variability in the chainline if used with the proper length bottom bracket. I
> suspect that is one of the main reasons Shimano went to this style of bottom bracket.

Hmm. I'm sure chainline variances due to where a crank sits on the taper are still well within
tolerances, even if a derailer adjustment is occasionally required. However, they may be appealing
to people who don't know any better.

> ISIS does not have this shoulder.

That's because ISIS' designers knew what a taper is for.

Matt O.

 

[Mike Demicco]

"Matt O'Toole" <[email protected]> wrote in news:[email protected]:

> Hmm. I'm sure chainline variances due to where a crank sits on the taper are still well within
> tolerances, even if a derailer adjustment is occasionally required. However, they may be appealing
> to people who don't know any better.

Guess you've never had the chain spontaneously derail off the middle ring when in the big cog, or
had the middle ring rub against the outer ring when in the small cogs. I have.

 

[Robin Hubert]

"Qui si parla Campagnolo" <[email protected]> wrote in message
news:[email protected]...
> doug-<< Can someone comment on the serviceability of the new DA Crank/BB?
> >><BR><BR>
>
> Simple answer is 'zero' serviceability., If the bearings go
south(hopefully
> not scoring the BB 'shaft'), ya replace them, about $40 per set.

The bearings would have to go all the way South to Seize-ville for the cart. to turn on the spindle.
I can't see this happening. BTW, the outer bits of those bearings look plastic. Any chance that the
contact with the spindle is plastic?

>
> doug-<< I know you can replace bearings, but would anyone expect there to
be a
> need to replace the BB spindle itself, and if so, am I correct in assuming that you'll need to
> replace the entire crank-arm/bb assembly? Is this a justifiable concern? >><BR><BR>
>
> Don't know if it is 'justifiable' but a hard crash with a bent right crank could be
> expensive...very complcated answer to a pretty simple question,
IMO-
> this crank design.
>

Yes, time will tell, but I suspect the "technology" will drop to lower pricepoints. Probably other
crank manufactures will also jump on the bandwagon.

My concern is actually the outside-the-shell bearings. I can picture the "cups" fatiguing at the
edge of the bb shell.

 

[Ted Bennett]

Mike DeMicco <[email protected]> wrote:

> "Matt O'Toole" <[email protected]> >
> > Hmm. I'm sure chainline variances due to where a crank sits on the taper are still well within
> > tolerances, even if a derailer adjustment is occasionally required. However, they may be
> > appealing to people who don't know any better.
>
> Guess you've never had the chain spontaneously derail off the middle ring when in the big cog, or
> had the middle ring rub against the outer ring when in the small cogs. I have.

Well, Mike, your chainrings must be seriously bent for the middle ring to rub against the
outer ring.

--
Ted Bennett Portland OR