see sheldon
Shimano RD set up here. Not sure how relevant the chain length instruction is for a single up front though.
Using the method Sheldon prescribes with a single front chainring will result in too short a chain.
BTW: Thanks for all the replies to this thread.
I still cant believe im having this much trouble. Could it be the fat CU 3/32 chainring im using? or the KMC chain? it seems pretty snug it def says 8 speed chain on the box. FUUUCK this is so frustrating.
I even realised that ive done a 1x6 speed before without a single issue.
goddamn.
Im going to try a different chainring and see if that works.
So it doesnt matter that that im using a 109mm/110mm BB? should i go to 107 or shouldnt it make a difference?
From your chainline description, a 107 would be an improvement, but it shouldn’t be a [www.nbc.com/30-rock/exclusives/dealbreaker/[/COLOR]]dealbreaker]([COLOR=#0e774a).
Try a different ring first. And front mech height / limit setup is all ok, still can’t eliminate rubbing over the entire range?
After that, go to a shop and throw yourself at their mercy.
So defeated.
(Fuckn cant wait for new 30Rock!!!)
Thanks again to everyone for their advice.
I’d suggest Commuter Cycles or similar shops for troubleshooting this sort of stuff. Shops that focus on sales would rather you buy a new bike. (even though that’s the mantra we preach!)
Im thinkn Abbotsford Cycles mostly because im Southside. What are their mechanics like? Commuter Cycles sound good otherwise.
Oh yeah, they’re a great place for this sort of thing. They dont’ even sell bikes!
I had a similar problem once and it turned out to be a badly installed connecting pin on the chain. Went with a quick link and the problem stopped.
What cranks are you running? Can you swap the chainring to the inside, or use some washers at the chainring to space it in a bit more as a test? A 107 BB will only bring the cranks in board by 1mm, so you should be able to test if that solves the issue before forking out for a new BB.
To confirm, you are talking about the front or rear derailleur here?
Does this approach assume people don’t cross chain?
Yes, but with only one chainring up front this method of determining chain length is incorrect and will be too short for the biggest rear cog.
“To confirm, you are talking about the front or rear derailleur here?”
Rear derailluer. The chain rubs against the chain plate when im in the 1st to about 4th gear.
Im running Shimano 600. (they look like 7400 cranks except have ‘600’ panto’d into em.)
I’ll try running the cainring on the inside but i got a feeling it will rub against the chainstay.
I think we need pics
But he does the setup in biggest-biggest.
Anyway, I just checked, I reckon his approach is bang on - in fact that is exactly the length my chain is. Could it be 1 link longer? Maybe.
But not routed through the derailleur, so even with the extra 1", the mech is pulled too tight to run big-big safely.
Oh, that’s a different kettle of fish. It shouldn’t do that at all. I once ran 6sp chain in a 7sp setup, cleared everything except the jockey cage and made some noise as it passed through.
If you have the right chain for the cassette (i.e. not a 5/6sp chain), then it sounds like something’s bent/misaligned. Best to get a fresh pair of eyes onit.
Check for yourself.
yeah im just going to take it down to Abbotsford Cycles.
Im done.
A broken man.
I need a drink.
I have 
I’ve used the big-big +1" and when shifting to that setup in the stand the cage is stretched too far for comfort for me. I still size chain like this, but I never go near the big-big or small-small gear combinations.
For 1 x setup I’d run the chain through the derailleur and over big-big and set the length such that there’s not an unacceptable amount of cage stretch or the chain is so long that the cage folds back onto the chain in high gear.
Shortsie; good luck, let us know what the culprit is.
And you can’t “run big-big safely”?
It’s obviously a balance between stretch and fold, and I always check the chain length in the manner you describe - run through the RD. On checking 2 bikes though, a 1x and a 2x they are as sheldon prescribed. Sure, it could be half a link longer on the 1x (though I’d really have to check if a full link would work) but it’s an MTB and I don’t want the chain slap. It’s not an issue on the 2x because only nuffies run small-small, big-big, but you could “run big-big safely”.