Aaargh SRAM Eagle skipping gears on cassette

[Riotsloth]

any chance the cassette itself is loose? the locknut on those is supposed to be done up to 40Nm...

Hi Fuzz

cassette seems solid.

I’m pretty sure now it just needs a delicate touch to it - not my clumsy inexperienced fingers!

 

[Cb750stu]

Hi I always thought the B screw was only for the granny gear set up only to get the correct gap so the derailleur doesn't hit the largest cog ??

I always set my gears with the gear cable un done ie no tension , the chain will automatically go to the smallest cog because there's no tension on the gear cable I make my adjustments , I'm sure SRAM calls for the chain to be slightly more to the right when positioned on the smallest cog , I push the derailleur by hand up onto the granny gear whilst peddling and adjust making sure it sits on the cog and doesn't go in to the spokes once that's done I let it go back down to the smallest cog , you don't need a lot of tension on the gear cable I just pull it by hand and secure , if the gears are slightly off mid cassette I make slight adjustments using the barrel adjuster,
I've always found SRAM to be easy to set up don't really bother with B screw if it looks ok I'm happy never had a issue tbh ,

Some decent videos on YouTube about setting up sram rear derailleur which I used ?

 

[Mikerb]

logically the B tension does 3 things. Firstly it ensures the top jockey wheel is far enough away from the largest cog to prevent the chain jamming against the cog. Second it pre loads the tension in the clutch of the mech so that there is sufficient tension when the chain is on the smallest cog. Thirdly, it enables enough length of chain between the bigger cogs and the top jockey wheel to enable the mech to move the chain from the biggest cog to the next biggest cog and the next. A sure sign of the gap between the top jockey wheel and the biggest cog being marginally too small is the chain hanging on the largest or second largest cog when changing gear down the cassette. This can change once a new chain develops a bit more sideways flex.
Slow or clunky changes from about the 3rd largest cog to the next 2 or 3 cogs going down the cassette is usually cured with a small adjustment at the selector.

 

[Riotsloth]

Top stuff Mike, thanks. I can fix it at the top via the barrel adjuster, but then it won’t go into the smallest cog happily!
I think I just need help from someone who knows what they are doing!

 

[Giff]

Hi Riotsloth
Did you ever get this sorted? I’ve got the same problem. The B screw does something but seems to move the problem up or down the cassette.
I’m going into my lbs on Saturday but thought you may have found a trick!

 

[Mikerb]

assuming the high and low stops are set correctly and the B tension is also properly set the only thing left that could cause skipping gears is cable tension. Other factors that can impact are too much cable friction, a bent or mislaligned hanger or derailleur cage, and a selector that is not functioning freely. It is the selector that determines how far the derailleur moves from one cog to the next...............if tension is too loose or too tight it cannot do that accurately.
B tension is best set with the SRAM white plastic guide (plenty of YT videos showing how), high/low end stops are set to align the derailleur cage with the outer edge of the smallest cog at one end of the cassette, and to prevent the chain going between the biggest cog and the spokes.

 

[Giff]

Hi Mikerb
Yes I’ve set the B gap with the shock at sag. It’s a Sram AXS deraileur and I have reset it to factory. The B screw alters the shifting but doesn’t cure it just moves it up the gears.

 

[Mikerb]

Hi Mikerb
Yes I’ve set the B gap with the shock at sag. It’s a Sram AXS deraileur and I have reset it to factory. The B screw alters the shifting but doesn’t cure it just moves it up the gears.

Ah..sorry...did not know you were talking about a GX AXS. Set up and adjustment is completely different apart from the B Tension adjustment. Check it out here:-

https://www.sram.com/globalassets/document-hierarchy/user-manuals/sram-mtb/drivetrain/eagle-axs-systems-user-manual.pdf

 

[JP-NZ]

Its one of the worst jobs on a MTB when it just won't shift right, then you get 90% of the cassette working but not the last. I just drop it to my LBS/Bike Mechanic and he works his magic in 25mins and charges $30. Job done and more hairs left on my head

 

[2WheelsNot4]

Anyone suggested the Hi/Lo yet ?.

Al this talk of hangers and B tension springs and more often than not its either the H/L or the cable has slackened off

 

[Mikerb]

Anyone suggested the Hi/Lo yet ?.

Al this talk of hangers and B tension springs and more often than not its either the H/L or the cable has slackened off

its AXS

 

[Giff]

its AXS

Solved!
I tried setting and re-setting everything. It changed things but didn’t cure it.
Here is the problem diagnosed by my lbs…..more experience and better eyes. A new casettte fixed it.