Duragrouch

I'm not intimately familiar with Octalink, but (correct me if wrong) the crank and BB cartridge are separate, and the latter comes in different lengths (to accommodate both doubles and triples), so there may be a mismatch, especially if the bike was bought used. As set up from the factory, it should be perfect. Also, if the outer chainring has been replaced, some chainrings are flat, and some are offset to the outside or inside, that would change things. Perhaps was originally offset to the outside and current chainring is perfectly flat, that would do it.

As with diagnosing most things, you check the easy stuff first. Like in Slingblade (lawnmower won't start) "It's outta gahyess."

Kontact

Octalink road came in two widths. If the problem is rubbing the outer chainring, that would only be caused by a chainline too far to the left. If it was the wrong spindle for a double, the crank would be too far to the right, because it would be the 118mm triple spindle.

The difference in chainrings is about 1mm. It is very hard to measure chainline to the exact 1mm from a round seat tube. So a chainline check isn't going to reveal a chainring problem. AND, the Octalink cranks had flat rings. Rings that are offset go the right, so the only "mismatch" of rings would improve the rub, not make it worse.

As I mentioned earlier, chainline concerns are a largely a product of the vast number of ways you can screw up putting together a square taper crank. Octalink, Isis, Hollowtech and other systems largely prevent that from happening because of the limited number of ways the crankset can be assembled.

Duragrouch

Your logic is flawless. Respect.

chiefkurtz 

If Calvin Jones from Park Tools has a video showing an RD adjustment for the smallest cogs, front and rear, it means Calvin intends me to use that combination. I'll never go against Calvin.

smd4

Hey, if you prefer a noisy drivetrain, I'm good with that. It'll let me hear you coming.

From the Shimano Dealer Manual:

wheelreason

LOL. One of my Pearl Isumi base layers has the tags on the outside at the waist, I always have to make sure I don't wear it inside out...

Duragrouch

"I feel that if Jacques Pepin shows you how to make an omelet, the matter is pretty much settled. That's God talking." - Anthony Bourdain

chiefkurtz 

Calvin and Jacques are two whose authority I'll never question. I do understand folks talking about non recommended gearing. I'm a vintage bike rider. This bike is a 1987 2x8, not a newer 10, 11, or 12. I did mention that in the OP. I believe non recommended gearing is a 'thing' with 10s, 11s, and 12s.

smd4

If you're a "vintage" bike rider, then you know cross-chaining has been advised against for decades.

chiefkurtz 

Yes, and since it's NEVER been an issue with me, on any of my bikes, for decades, I've given it the consideration it warrants; none.

smd4

Very good then.