Another BB(length) choice question

[dabac]

Hi guys,
This is my first foray into Italian thread BBs, which means my earlier approach of either straight off replacements or test fitting stuff until it lines up isn't working for me, as I haven't got any parts apart from the take-off to tinker with. And what has come off is a bit suspect for various reasons.
Anyhow, the crank I want to use is a Shimano Nexave FC-C600 (http://techdocs.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/FC/EV-FC-C600-2069A_v1_m56577569830608872.pdf). The tooth count would fit the speed requirements of the bike's rider.
(I'm guessing I might have to cut out that cam thingy on the inside of the chaingring spindle, which I'm guessing has something to do with front shifting.)
According to herehttp://techdocs.shimano.com/media/techdocs/content/cycle/SI/Nexave/C600/SI-F971A-EN_v1_m56577569830613207.pdf) a 117.5 mm BB would give me a 52.5 mm chainline.
But according to Sheldon Brown (http://www.sheldonbrown.com/chainline.html#adjfront) for a 2x 9 road bike I should shoot for a 43.5 mm front chainline.
9 mm off seems quite a lot.
I've found Italian thread, square-taper BBs here:http://www.chainreactioncycles.com/se/en/shimano-un55-square-taper-bottom-bracket/rp-prod71369 in: 107, 110, 113, 115 mm.
But which one to go for?
107 would put me closest to the general recommendation. But then there's that "special" feature of the crank, maybe it has more than average inside protrusion? Perhaps the 110 is a safer bet? 0r even 113?

Or should I just drag the bike to a LBS and have them trial fit stuff until it works?

Any hints would be appreciated.

 

[CAMPYBOB]

Measure the existing 9-speed cassette centerline and verify the chainline with the existing crankset.

You're installing one of those ratcheting cranksets?

 

[dabac]

Measure the existing 9-speed cassette centerline and verify the chainline with the existing crankset. You're installing one of those ratcheting cranksets?

Kinda-sorta. I got it mainly b/c it seemed like an inexpensive way to a suitable tooth count. It looked quite nice too. I am quite ready to cut the "cam" out if need be as I have no intention of using it. On top of that I don't know how it's supposed to work, and I don't have any of the associated parts. Previous BB was cup&cone, with the axle run in reverse, so I don't know how useful that comparison would be. But I guess I can measure the cassette.

 

[alfeng]

FWIW. I didn't have-or-use the full variety of available Shimano square taper spindles, but MY impression was that the 107mm, 110mm, & 115mm were symmetrical whereas the 113mm spindle was asymmetrical (with the LONG side on the non-driveside) ...

BTW. It was/(is?) that lack of consistency in the implementation of the square taper which made me an instant fan of the now-obsolete Octalink BBs!!!​

By my reckoning, the offset of the taper on the driveside of the 113mm spindle is essentially equivalent to the offset of the taper on the 107mm symmetrical spindle ... Regardless, this may be stating the obvious ... If you know the spindle length (i.e., type) that you would use when the particular crank is mounted with an English threaded BB, then THAT is the spindle length you want when the crank is mounted with an Italian threaded BB (some caveats) ... YOU can 'test' the type of spindle the crank would use by slipping the driveside onto ANY installed square taper spindle & then note the distance between the end of the crankarm & the chainstay ... AND THEN, slip the non-driveside arm onto the driveside taper & note the distance between the end of the crankarm & the chaninstay ...

So, if the non-driveside crankarm's exhibits the same gap from the chainstay as the driveside arm then the particular crank uses a symmetrical BB spindle AND you probably want a 107mm spindle if it is a steel frame & possibly a 110mm ... ... but, probably (but, not necessarily) a 115mm spindle if it is an aluminum frame (it mostly depends on the width of the stays + the dropout spacing) ...

... with 135mm dropouts, I would probably opt for the 115mm spindle, BTW, if the cranks called for a symmetrical spindle.​

Regardless, unless you are using the crank on a Single COG installation, even the 115mm will probably be "okay" with either a steel frame or aluminum frame ...

• I think that the problem of the chain being pulled off the inner Chainring could present itself when the chain is shifted onto the largest Cog if too long a spindle is used.

 

[oldbobcat]

What Campybob said. Chainline is everything, unless the correct chainline causes something on the crank to hit the frame.

My experience may be limited here, but I've never met a JIS road double crank that didn't use a 107-110 mm bottom bracket to line up to a 126 or 130 mm rear axle.

Generally, 113-115 mm is for road triples; 117-122 mm for MTBs and hybrids with triple cranksets and 135 mm rear axles.

 

[CAMPYBOB]

The 'freewheeling' cranksets may be a bit bizarre. Especially if it has dished chainrings or offset spider to compensate for an external pawl assembly. I was under the impression that with indexed shifting, ramped tooth profiles and the like that they had disappeared from the market.

In my area, they were only seen on inexpensive department store bicycles.

 

[dabac]

Originally Posted by CAMPYBOB
The 'freewheeling' cranksets may be a bit bizarre. Especially if it has dished chainrings or offset spider to compensate for an external pawl assembly. I was under the impression that with indexed shifting, ramped tooth profiles and the like that they had disappeared from the market.

In my area, they were only seen on inexpensive department store bicycles.

A freewheeling crankset may well be a bit bizarre, but this isn't one of them. Admittedly it has a funny seal and some sort of drive flange on the inside of the RH crank, but the rest seems to be an entirely normal square taper. Arm + carrier for the rings is one solid unit. Maybe it'll sit further out than normal, maybe the center piece is thicker than normal, something like that.
But mated to a regular square taper BB I can't see why it wouldn't work like any other crank.

And the hubs that I've looked at in the same series of components all seems to have pretty much bog-standard freewheeling capacity.

 

[alfeng]

Originally Posted by oldbobcat
What Campybob said. Chainline is everything, unless the correct chainline causes something on the crank to hit the frame.

My experience may be limited here, but I've never met a JIS road double crank that didn't use a 107-110 mm bottom bracket to line up to a 126 or 130 mm rear axle.

Generally, 113-115 mm is for road triples; 117-122 mm for MTBs and hybrids with triple cranksets and 135 mm rear axles.

FYI. During the advent of square taper BB spindles, the 113mm was THE spindle length for many Doubles ...

• AFAIK, both JIS (Shimano) & ISO (e.g., Campagnolo, Sugino, etc.) used asymmetric 113mm spindles back in the early days for Doubles ... I have had MANY 113mm spindles (Shimano & Sugino) and all were asymmetric
• I don't know what the length of the spindle was for my Nuovo Record crankset, but I believe it was also 113mm ... it was asymmetric THIS is another instance where I believe that Sheldon Brown (& John Allen) has (have) misinformation on the sheldonbrown.com website
• ALSO, all of MY (vintage) Sugino spindles were ISO

• I had more than one 113mm (Shimano) square taper CARTRIDGE BB which had an asymmetric spindle ... none of the 113mm spindled square taper BBs which I have owned had symmetric spindles ...

• AFAIK, it wasn't until the 90s (?) when Shimano 7400 (¿7410?) cranks adopted symmetrical spindles that the use of asymmetrical spindles began to wane ...

• The use of symmetrical square spindle BBs was re-enforced when Campagnolo adopted a symmetrical 102mm spindle for their Record/Chorus cranks in ~1998 (with those lesser Campagnolo cranks maintaining an asymmetric spindle until the bitter end).

¿i¿Am I living in a separate reality?!?​

​

PERHAPS!!!​

 

[oldbobcat]

Thanks. My Campy Record spindles were 108 mm, I think--68 and 70 mm shells. I don't remember measuring the BB that came with the Stronglight 93 that I put on my Raleigh Super Course. All of these spindles were asymmetric, though.

 

[dabac]

Hi all,

I'll be away from the bike in question for a couple of weeks, so I'll thank you for the pointers so far and hopefully be back with an update eventually.