SRAM chain length

Morning all,

Followed the SRAM manual last night when installing a new 12 speed mech/chain which said to measure the correct length of chain with the suspension at full compression and wrapped around the biggest gear and chain ring but not through the mech – this resulted in a chain that’s so saggy it falls off in the lowest/most difficult gear and touches the chain stay at rest which obviously ain’t right.

Does anyone else bother to measure at full compression or should I just stick with wrapping it around the biggest gear/chainring as I’ve always done???

Assume you have the b tension set right 

Assume you have the old one and it worked…why not match the new one, links wise, to that? 

Assume you have the b tension set right

Their road groupsets come with a nifty plastic tool for setting this up…

https://www.sram.com/globalassets/document-hierarchy/service-manuals/sram-drivetrain-adjustment-tools.pdf

I’ve never measured at full compression, because you get a chain that’s well, you know the rest

Recently replaced the mech, cassette and chain on my bike. Followed the SRAM guide when setting up with the B-tension set and also compressed the suspension and it worked a treat for me…

Ah, yeah, I hadn’t set the B tension yet so maybe that explains it.

I would have used previous chain but that had some jamming issues which eventually led to the old mech getting stuck in the spokes and ripped off so not sure the length was correct on that one either.

Are you counting the correct number of extra links? A link is a single one, not a pair.. it seems to cover it fairly clearly in the docs but just thought I’d check.

Actually looking at the manual again, the B tension wouldn’t make a difference as the chain isn’t threaded through the mech when measuring the “correct” size:

Are you counting the correct number of extra links? A link is a single one, not a pair.. it seems to cover it fairly clearly in the docs but just thought I’d check.

Yeah, I cut it exactly as per the above image.

Oh wait, the correct B tension would take up the slack???