What are these BB numbers telling me?

[TomYoung]

Hi all:

Shortly I'll start building up a new touring bike (Surly Long Haul
Trucker) and I'm researching suitable parts. In looking at the Shimano
site's information about the OCTALINK Bottom Bracket (BB-ES51) to go
with a Deore crank I see the following specifications:

OCTALINK
Splined Mount YES

Chain line 47.5mm 50mm

B.B. Shell Width 68/73mm

Spindle Length 113mm 118mm

Am I correctly reading this that if I want a chainline 47.5mm from the
center of the bottom bracket I'd select a 113mm spindle, and a 118mm
spindle results in a 50mm chainline?

So I guess the process is to mount the rear wheel with cassette,
determine the distance from the bike's center to the middle cog, and
then select the spindle that get's me closest to whatever number I come
up with?

TIA.

Tom Young

 

[Nate Knutson]

TomYoung wrote:
> Hi all:
>
> Shortly I'll start building up a new touring bike (Surly Long Haul
> Trucker) and I'm researching suitable parts. In looking at the Shimano
> site's information about the OCTALINK Bottom Bracket (BB-ES51) to go
> with a Deore crank I see the following specifications:
>
> OCTALINK
> Splined Mount YES
>
> Chain line 47.5mm 50mm
>
> B.B. Shell Width 68/73mm
>
> Spindle Length 113mm 118mm
>
> Am I correctly reading this that if I want a chainline 47.5mm from the
> center of the bottom bracket I'd select a 113mm spindle, and a 118mm
> spindle results in a 50mm chainline?
>
> So I guess the process is to mount the rear wheel with cassette,
> determine the distance from the bike's center to the middle cog, and
> then select the spindle that get's me closest to whatever number I come
> up with?
>
> TIA.
>
> Tom Young

You're correct about what the numbers mean. If you're going with this
crank, get the 113. The rear chainline (distance from center plane of
bike to middle cog) for any 135-spaced cassette hub won't change much
at all. The wider chainline "options" you're seeing here are because
many MTBs have clearance or derailer travel issues and are forced to
have a chainline that's a few mm out in front. Shimano is saying here,
"Yes, it's ok to run this with a messed up chainline because that's how
things are."

Most of the cool kids set up their LHTs with Sugino XD600's.

 

[Qui si parla Campagnolo]

TomYoung wrote:
> Hi all:
>
> Shortly I'll start building up a new touring bike (Surly Long Haul
> Trucker) and I'm researching suitable parts. In looking at the Shimano
> site's information about the OCTALINK Bottom Bracket (BB-ES51) to go
> with a Deore crank I see the following specifications:
>
> OCTALINK
> Splined Mount YES
>
> Chain line 47.5mm 50mm
>
> B.B. Shell Width 68/73mm
>
> Spindle Length 113mm 118mm
>
> Am I correctly reading this that if I want a chainline 47.5mm from the
> center of the bottom bracket I'd select a 113mm spindle, and a 118mm
> spindle results in a 50mm chainline?
>
> So I guess the process is to mount the rear wheel with cassette,
> determine the distance from the bike's center to the middle cog, and
> then select the spindle that get's me closest to whatever number I come
> up with?
>
> TIA.
>
> Tom Young

It can be used for either a 73mm BB shell or a 68mm BB shell(the Surley
is 68mm) and can use either of the spinle lengths, the longer one
mostly for 73mm shells and rear suspension. So 113mm and 68mm is what
you need for the Surley. Chainline will take care of itself with this
frame.

 

[TomYoung]

> It can be used for either a 73mm BB shell or a 68mm BB shell(the Surley
> is 68mm) and can use either of the spinle lengths, the longer one
> mostly for 73mm shells and rear suspension. So 113mm and 68mm is what
> you need for the Surley. Chainline will take care of itself with this
> frame.

Thanks for the info. I'm getting parts piecemeal from various places
and would certainly like to have all the bits fit properly the first
time around.

 

[[email protected]]

Nate Knutson wrote:
> TomYoung wrote:
> > Hi all:
> >
> > Shortly I'll start building up a new touring bike (Surly Long Haul
> > Trucker) and I'm researching suitable parts. In looking at the Shimano
> > site's information about the OCTALINK Bottom Bracket (BB-ES51) to go
> > with a Deore crank I see the following specifications:
> >
> > OCTALINK
> > Splined Mount YES
> >
> > Chain line 47.5mm 50mm
> >
> > B.B. Shell Width 68/73mm
> >
> > Spindle Length 113mm 118mm
> >
> > Am I correctly reading this that if I want a chainline 47.5mm from the
> > center of the bottom bracket I'd select a 113mm spindle, and a 118mm
> > spindle results in a 50mm chainline?
> >
> > So I guess the process is to mount the rear wheel with cassette,
> > determine the distance from the bike's center to the middle cog, and
> > then select the spindle that get's me closest to whatever number I come
> > up with?
> >
> > TIA.
> >
> > Tom Young
>
> You're correct about what the numbers mean. If you're going with this
> crank, get the 113. The rear chainline (distance from center plane of
> bike to middle cog) for any 135-spaced cassette hub won't change much
> at all. The wider chainline "options" you're seeing here are because
> many MTBs have clearance or derailer travel issues and are forced to
> have a chainline that's a few mm out in front. Shimano is saying here,
> "Yes, it's ok to run this with a messed up chainline because that's how
> things are."
>
> Most of the cool kids set up their LHTs with Sugino XD600's.

A much better choice than anything that uses an Octalink BB, IMHO.

 

[TomYoung]

Nate Knutson wrote:

> Most of the cool kids set up their LHTs with Sugino XD600's.

I'm leaning toward a splined bottom bracket setup. In a review of the
Long Haul Trucker in Adventure Cycling the article discusses the
components of a complete kit available from Surly for the bike. The
crank is listed as Sugino - no model number stated - "with splined
cartridge bearing spindle." The accompanying picture of the built-up
bike has a crank that looks like the XD600 (can't really tell) but as
far as I can see the touring triples from Sugino are all square-taper.
Hence, I'll probably use a Deore crank with 48/36/26.

Thanks.

 

[TomYoung]

[email protected] wrote:
> Nate Knutson wrote:

> > Most of the cool kids set up their LHTs with Sugino XD600's.
>
> A much better choice than anything that uses an Octalink BB, IMHO.

Would you expand upon that? For technical reasons or perceived wider
availablity?

 

[[email protected]]

TomYoung wrote:
> [email protected] wrote:
> > Nate Knutson wrote:
>
> > > Most of the cool kids set up their LHTs with Sugino XD600's.
> >
> > A much better choice than anything that uses an Octalink BB, IMHO.
>
> Would you expand upon that? For technical reasons or perceived wider
> availablity?

There are known problems with the crankarm/spline interface in the
Octalink design. This is the reason that Shimano is in the process of
"walking away" from the design. IMO, in a few years, Octalink BBs and
cranks will be out of production and hard to find. Shimano has done
this sort of thing in the past, so there is ample precedent. Why commit
yourself to a design that is headed for extinction?

In the larger sense, Octalink was a "solution in search of a problem",
a design driven more by marketing than by engineering. The same is true
of the ISIS BBs and cranks, IMO.