You wrap the chain around the chainring and largest cassette cog and add 4 links for full suspension bikes (with suspension fully compressed) or 2 links for a hardtail. Once routed through the derailleur the length will be right.

 

4 links for the hardtail, 2 for the full suspension. Seems backwards, but that's what's in the manual.

 

4 links for the hardtail, 2 for the full suspension. Seems backwards, but that's whats in the manual.

Yes, that's what I meant to write but got it backwards.

 

If you don't have SRAM instructions get them and follow them for derailleur setup...website also has a good video. The 'B-gap' tool is useful but you can use a small metric ruler. The 'gap' is 15mm from top of upper jockey wheel to bottom of biggest cog on cassette with susp compressed.

Park tool site has good videos on proper chain sizing

 

So you measure from the tip of each tooth to get the 15mm distance? Or inbtween 2 teeth on the upper jockey to the tip of one of the teeth on the cassette.

 

The SRAM directions are indeed correct. On a FS bike you need to compress the shock to the point of MAX chain growth, and then measure the chain and add two links. This means when the suspension is not compressed and there is less chain growth, you will have MORE than 2 links overlapped. It will probably be closer to 4 links overlap when uncompressed, depending on your suspension. The important thing is that you measure at MAX chain growth, that way the chain can never be pulled any tighter by suspension travel.

 

Here it is, visual representation

 

I put the chain on full length, and then removed one link and test fitted, removed another link etc... until it fit right.

 

I agree that's the most foolproof way for the home mechanic who isn't trying to save a couple minutes.
And it'll let you see what the shortest possible chain you can get away with is.

 

get the b tension tool and follow the sram instructions. If you do not setup eagle right it will not only never perform correctly but you risk derailleur destruction. eagle isn't forgiving with setup, you either do it right and it's the best drive train you've ever owned, or you don't and you hate it. Read the entire eagle thread in this sub forum for context.

For reference, there is plenty of info on the question you asked in that thread already. There was no need for a new thread.

 

Unnessesary strain on the drive train by maxing out the derailleur travel when on the biggest cog. A bad landing, hammering hard enough to flex too much and there goes the chain, derailleur or cassette

And SRAM screwed up instructions big time. Probably the cause of all the early reports of bent 50t cogs.

Doesnt matter what drivetrain. Eagle or shimano 1x10. Its big ring big cog and plus 2 links. For full suspension you compress to max chain growth then big, big plus 2 links.

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And SRAM screwed up instructions big time.

Why do you think that? If their instructions were an error that was costing them warranties and reputation I think they'd make a revision. The instructions basically say what you said, big/big +2 with the suspension at full growth. They do ask for more chain (big/big + 4 links) on a hardtail but that would put less stress on the 50t.

 

I had a full suspension single speed (IGH) setup for a while, and the chain was too short. Near the bottom of the travel, it would run out of chain and thump like it was hitting something solid, but it was just the lack of more chain. Somehow I never broke it, and once i figured it out, I put a link back.

 

I didnt see the part about at full growth. I dont have Eagle (far from worth the money imo) and seemed like from the convo here something wasnt right about the instructions.

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I think there is some confusion as to why they ask for +2 links on full suspension and +4 links on a hardtail because it seems like it might be the opposite, but after thinking about it that makes sense to me now.

 

why not err on the longer side? dropped chains on a narrow wide/clutch combo are rareer than flats on a tubeless setup.

 

I agree, slightly long beats slightly too short.