Shifting issue on new 1x11 drivetrain - possibly chain length?

[lechatnoir]

I'm finally building by gravel bike frame up. Groupset is SRAM 1x11 Apex with 38t chainring on 10-40 cassette. I have an 11sp KMC chain.

 

It's all together with the chain at its full length (not sure how many links) Shifting from small to large works fine until the last cog - it shifts UP, but immediately shifts back down and then makes a racket.

 

Anyone out there in Hubland that can steer me in the direction of a solution? Could it be chain length? There is quite a bit of tension from the derailleur on the chain when on the smallest cog

TIA

T

[Eldron]

Limit screw on the top needs a quarter turn out?

 

Edit - also check if the pulley wheel is touching the 40t ring. It's common on big cassettes and makes a noise like you're describing.

[lechatnoir]

Limit screw on the top needs a quarter turn out?

 

Edit - also check if the pulley wheel is touching the 40t ring. It's common on big cassettes and makes a noise like you're describing.

Thanks!

 

Should have added that b-screw seems good on the 40t cog. that limit screw may be an issue. Will check this evening. Oddly, at the limit, it didn't seem to make the derailleur move - it's almost as if the derailleur is at its limit without the screw engaging (if you know what i mean)

[gemmerbal]

It could also be the B tension screw, if theres not enough room to properly shift over. also check your chain length by running it over the chainring and the granny gear without going through the derailleur, and then add 2 links, some swear by this method of sizing your chain - it worked for me.

[gemmerbal]

sorry some of my comments got addressed by your simultaneous reply.

 

chain length, check it.

Thanks!

 

Should have added that b-screw seems good on the 40t cog. that limit screw may be an issue. Will check this evening. Oddly, at the limit, it didn't seem to make the derailleur move - it's almost as if the derailleur is at its limit without the screw engaging (if you know what i mean)

[droo]

When all else fails, click here...

[dirtypot]

When all else fails, click here...

 

But try every other conceivable thing before implementing this solution...