Chain Suck - Shimano Octalink Triple

Broadside

Guru
Location
Fleet, Hants
I've been a bit stupid and removed the large and middle chainrings for cleaning on my Specialized Secteur Sport without noting which position the middle chain ring was in.

The large chainring was obvious because it has a stub which sticks out to prevent the chain from getting caught between the chainring and the crank arm. However there was no obvious mark on the middle chainring so I just went ahead and removed it thinking it wouldn't matter how I put it back on.

I am now getting chain suck when down shifting under load from the large to the middle chain ring, and after checking Sheldon and his reference to Jonathan Levy it appears the problem might be because the middle chain ring is out of teeth alignment with the large one. I have checked the chain for wear and I am just approaching the 1/16" mark so I don't think chain wear is the issue yet.

So I have the option of rotating the middle chain ring one position at a time but with four potential positions to try this may take a while as the chain does not suck on every down shift, it's probably one in 20.

Does anyone know of a quicker/easier way to work this out or is it simply trial and error and a few more scratches on the chain stay due to the chain jamming?
 

woohoo

Veteran
There are markers. Sometimes it's a little triangle stamped on the chainring or a rounded pointer on the inner circumference of the chainring that line up with the crank. I'm sure the Shimano site shows the alignment markers.
 
OP
Broadside

Broadside

Guru
Location
Fleet, Hants
Thanks woohoo, the tech doc on the Shimano website does show a marker on the chain ring and I've just checked my bike and it is out of line.

That'll be a job for the weekend then, many thanks for the tip.
 

Crankarm

Legendary Member
Location
Nr Cambridge
Please find attached a pic of the reverse side of a Shimano Ultegra Octalink chainset showig the aligning lugs on the rings which should all align with the crankarm :biggrin:. The peg on t'other side of the largest chain ring is also aligned with the crank as are the lugs on the middle and smallest ring. I think you've already realised this though judging by the above posts.

You can also see the chainset is pretty clean. This is because it is brand new unused. I wouldn't have it on the bed if it weren't :biggrin:.

HTH.
 
OP
Broadside

Broadside

Guru
Location
Fleet, Hants
Well I rotated the middle chain ring round to the right position and have had no further problems. The chain seems to shift more easy too, I'm surprised I put up with it for a couple of hundred miles before sorting it out.

Anyway all sorted so thanks for the help.
 
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