Aaargh SRAM Eagle skipping gears on cassette

[Riotsloth]

Afternoon all

Just before repeatedly banging my head against a wall, I thought I'd post up here. I have just fitted a new 12 speed Eagle GX derailleur to my Cube Stereo Hybrid 120. The bike was new in November and had a slightly bent Eagle derailleur so I decided to upgrade to a GX. I've got that on okay using the installation instructions, and everything seems to be as it should. My B screw and upper and lowers are bang on, but can I get the bloody gears to index smoothly? It jumps gears in the centre of the casette, and graunches and crunches on certain gears depending on the barrel adjustment. I can't seem to get it bang on. When I put the cable on I turned the barrels out ten clicks to allow for adjustment either way FYI.

Has anyone got some top tip any all? Other than 'set up 1000 of them and it will get easier'?

I'd be most grateful for any help!

Thanks

Robsa

 

[Jackware]

Did you replace the hanger at the same time?
If you managed to bend the derailleur the hanger will be as well.
And it's always good to have a spare so buy a couple.

 

[Riotsloth]

Did you replace the hanger at the same time?
If you managed to bend the derailleur the hanger will be as well.
And it's always good to have a spare so buy a couple.

Hi there


Yes, brand new hanger too.

 

[Jackware]

Hi there


Yes, brand new hanger too.

Ok, the next silly thing I've done in the past is thread the chain around the jockey wheels incorrectly, the wrong aide of the guide plate.
I'd also keep adjusting the b screw in very small increments.

 

[Riotsloth]

Ok, the next silly thing I've done in the past is thread the chain around the jockey wheels incorrectly

Ha, I did that first time! Soon realised my error. The B screw alignment is exactly on with my weight on the bike using the SRAM tool, would I be increasing the distance from the cassette I presume?

 

[Mikerb]

So going back to the beginning...you changed the rear mech because it was slightly bent. I assume you had some gear changing issues and diagnosed a slightly bent mech as the cause?
So what were the original gear change issues ..if any?

what you are experiencing now sounds like a mix of issues. If the jumping of gears in the middle of the cassette is when runing the chain from large to smaller cogs, that is fairly typical of wrong B tension adjustment. Personally, I do not find the spacer tool particularly useful! I have the 11 speed GX. I set the b tension so that the top jockey wheel is as close to the largest cog as possible without the chain getting jammed. Then check the shift down from the largest cogs to 3/4 cogs down the cassette increasing the B tension gap progressively until I get smooth changes. Typically when the B tension gap is very close the change down will hang on 9 or 10, once release a little it no longer hangs but is slow, released a little further and the gear change is good. It is worth re-checking the limit adjustments having done that. Then you can play with cable tension at the bars which is more likely to impact on gears in the middle of the cassette.

If you still have problems after those adjustments you have a worn/damaged chain or cassette or both.

 

[Riotsloth]

Thats great, I'll try adjusting the B tension tomorrow. Many thanks.

 

[Mikerb]

ps..... just for clarity on the a bove, I do the b tension adjustment with the bike in a stand so the rear wheel is hanging...no bike weight on it..and not with the bike at its rear shock sag point.

 

[>moto<]

When I put the cable on I turned the barrels out ten clicks to allow for adjustment either way FYI.

Mid gear jump sounds like B-Tension as others have said. Also, 10 clicks seems like too much, and when are you adding it?

You should put the chain/shifter on the smallest rear cog, undo the cable at the derailleur and then phyically move the gears up and down the cassette whilst pedalling (by hand). You can use your other hand to push the derailluer to change gear. Set the high and low limits as needed.

Then, pull the cable so it has light tension at the derailleur and tighten the screw to hold it in place. All this should be done with the adjuster wound all the way in, then backed off max 4 clicks. Then add tension to the adjuster as needed until you get good up and downshifts.

Or just look up a GMBN or similar video

 

[Riotsloth]

Mid gear jump sounds like B-Tension as others have said. Also, 10 clicks seems like too much, and when are you adding it?

You should put the chain/shifter on the smallest rear cog, undo the cable at the derailleur and then phyically move the gears up and down the cassette whilst pedalling (by hand). You can use your other hand to push the derailluer to change gear. Set the high and low limits as needed.

Then, pull the cable so it has light tension at the derailleur and tighten the screw to hold it in place. All this should be done with the adjuster wound all the way in, then backed off max 4 clicks. Then add tension to the adjuster as needed until you get good up and downshifts.

Or just look up a GMBN or similar video

Thanks, I may give that a go. I wound the barrel right in, then out 10 clicks as that is one complete revolution. Then I tensioned the cable. I have ordered a hanger alignment tool so will try that as well. high and low seem perfect, the hanger is new, the derailleur is new, the chain and cassette are new 150 miles ago (November). I am growing to develop a deep resentment of SRAM 12 speed shifter adjustments!

 

[>moto<]

Thanks, I may give that a go. I would the barrel right in, then out 10 clicks as that is one complete revolution. Then I tensioned the cable. I have ordered a hanger alignment tool so will try that as well. high and low seem perfect, the hanger is new, the derailleur is new, the chain and cassette are new 150 miles ago (November). I am growing to develop a deep resentment of SRAM 12 speed shifter adjustments!

Does it drop onto the bottom (smallest) cog easilt when you change gears? 1 turn on the adjsuter should be fine. I didn't remember it being as many as 10.

All else being equal, once you have done the above, you should be able to wind all the tension off and just keep adding it until it goes up through the gears nicely.

Whilst you are waiting for hangar alingnment tool, you can put your chain onto the smallest gear and look at the bike from behind, the jockey wheels should line up directly under the small cog. If they don't, that's the goal.

 

[Riotsloth]

Low and high gears seem to be fine, it's the middle ones it jumps over, which is the reason I think some people suggest it may be a hanger alignment problem.

 

[Mikerb]

You did not answer my question earlier on..............in my earlier post I asked what gear change problems you were experiencing that led you to investigate and decide the mech was slightly bent?

Even a slightly bent mech is still capable of being indexed albeit it may not be possible to get both limit screw adjustment right. A slightly bent mech can often be straightened by hand.

You may have misdiagnosed in the first instance and having replaced virtually everything you still have problems because the original fault is still there.

Your bike is c 3 months old so unlikely chain or cassette are worn in that time.

What you have not mentioned is the shifter or gear cable. A gear cable with too much friction can cause gear change hesitation.

 

[Riotsloth]

Hi Mike

Regarding initial problems - it was a similar problem in fact - trouble with centre rings of cassette jumping a gear on the way from biggest cog to smallest. The mech was bent on arrival from new - damaged in transit. Of course I didn’t realise until I took it to LBS with shifting problems and they looked at it and told me. I fitted a brand new hanger and LBS bent the mech slightly and it worked again, but then I had an off and it went - must have been the hanger getting slightly bent.

Shifter cable is fine - I had to shorten it when going from Eagle to Eagle GX so I know it’s perfect.

My hanger alignment tool arrived today and my hanger was waaay out; about 12mm from side-to-side of rim (9 to 3) and about 6mm (12 to 6). I have now straightened it and my new chain arrives soon (old chain has a couple of tight links which I can’t seem to loosen up), which I will fit when it arrives (also, didn’t realise also that the quicklok link on SRAM chains is a use once and throw either, I’ve ordered a few spare now). So fingers crossed, once that’s on it should be okay!

Never had these problems on my 10-speed Viscount racer!

I shall update once the new chain is fitted - thanks for the help so far everyone.

Robsa

 

[The EMF]

Hi....I had a similar problem to yours, I replaced the shifter cable. I know you’ve not done any mileage to warrant the cable being worn but it could have been kinked when it was installed new as mine was.

 

[Riotsloth]

Hi....I had a similar problem to yours, I replaced the shifter cable. I know you’ve not done any mileage to warrant the cable being worn but it could have been kinked when it was installed new as mine was.

Thanks for the suggestion! I think it’s fine as I had to shorten it for the new mech.

 

[The EMF]

Thanks for the suggestion! I think it’s fine as I had to shorten it for the new mech.

My cable had been kinked further up the inside of the outer and was tight inside so preventing consistent shifting.....if you get my drift

 

[p3eps]

SRAM recommend the quick links are only used once so they can make money on you buying replacements all the time.
In reality, you can use them over and over again without any issues. I’ve had mine on and off at least 10 times so far and have no problems. I do have a few spares in the event of an issue though... and carry one on the trails with me.

 

[Riotsloth]

My cable had been kinked further up the inside of the outer and was tight inside so preventing consistent shifting.....if you get my drift

Yes, know exactly what you mean. Mine is fine, I had to pull it out about 6 inches or so to shorten the outer cable when fitting the GX mech so I know it moves smoothly back and forth.

 

[The EMF]

Yes, know exactly what you mean. Mine is fine, I had to pull it out about 6 inches or so to shorten the outer cable when fitting the GX mech so I know it moves smoothly back and forth.

That’s good, hope you’re sorted now.

 

[Riotsloth]

That’s good, hope you’re sorted now.

Not yet! I want to jump out of a window. It now has the new GX chain on and shifts smoothly between all gears apart from the two smallest ones which it hops between and graunches. Aaaaaaargh!!!!!!

So I am going to take the chain off again, take the mech off, check the hanger alignment (AGAIN), re-fit the mech, check the A and B screws, re-fit the barrel adjuster cable, re-fit the chain, Check B screw and try again!

 

[Jackware]

There's no play in the frame or bearings is there, allowing the rear triangle to move about allowing the relative position of the derailleur and cable tension to change?

(This is just me wondering idly as you've seemed to have covered all the other angles)

 

[The EMF]

Not yet! I want to jump out of a window. It now has the new GX chain on and shifts smoothly between all gears apart from the two smallest ones which it hops between and graunches. Aaaaaaargh!!!!!!

So I am going to take the chain off again, take the mech off, check the hanger alignment (AGAIN), re-fit the mech, check the A and B screws, re-fit the barrel adjuster cable, re-fit the chain, Check B screw and try again!

Deep breath’s and count to ten ??

 

[Riotsloth]

There's no play in the frame or bearings is there, allowing the rear triangle to move about allowing the relative position of the derailleur and cable tension to change?

(This is just me wondering idly as you've seemed to have covered all the other angles)

All that seems fine. It's probably just a combination of being a bit fiddly and me being out of bikes for 20 years!

 

[Stihldog]

Well I’m learning a few things here.…and stay away from open windows ?.
I have had similar problems when I changed over to a GX derailer and cassette. Was the hanger though.
Since then I ordered the derailer alignment tool, just to eliminate that problem.

 

[>moto<]

Not yet! I want to jump out of a window. It now has the new GX chain on and shifts smoothly between all gears apart from the two smallest ones which it hops between and graunches. Aaaaaaargh!!!!!!

So I am going to take the chain off again, take the mech off, check the hanger alignment (AGAIN), re-fit the mech, check the A and B screws, re-fit the barrel adjuster cable, re-fit the chain, Check B screw and try again!

Re-check your low stop screw adjuster before you do all of that.

 

[Fuzz]

Sounds like the hanger may be ever so slightly loose (doesn't take much loss of tension on the mounting screws to make it wobble) or that your hanger is slightly bent, (usually they need a small tweak towards the outside in this scenario with a pair of adjustable pliers or something). Both hangers and detailleurs, can take a small amount of flexing by hand to align them (in my experience). I had the exact same problem with mine during this last week, and it was the hanger mount screws being slightly loose, and the hanger needing a small bend to the outside, and the derailleur itself a small bend by hand. Very small adjustments, and now it's changing gears flawlessly, like it was brand new. (it has 1000kms on it). It took me 3 hours of pulling my hair out, and doing micro adjustments. I assume you also are doing small adjustments to the cable tension, with the adjustment screw near the hand lever? Mine is a 12 speed, and it was the middle couple of cogs that were being the most difficult...

 

[Riotsloth]

Hi all

Thanks for all the replies, but I have given up. It shifts perfectly from the highest gear all the way up to the largest, but going the other way it jumps 2nd and grinds away on 3rd but after that is perfect. As I almost never use these gears that’s the way it’s going to stay until I can get it to the LBS.

I have:

Fitted brand new GX chain
Brand new GX Mech
shortened the cable, checked it isn’t binding anywhere so it fits exactly as shown in mech manual
set barrel tension to four clicks out then tightened the bolt (to the correct torque using a torque wrench)
Checked hanger alignment using an alignment tool. Three times. It’s within a mm across 0, 90, 180 and 270 degrees
Used the correct (white) SRAM Mech alignment tool to check the B screw alignment.
Checked both high and low screws are correct. As the chain goes into top and bottom gears without a problem, I have no reason to think there is a problem with them.
If the barrel adjuster moves from four clicks out things just get worse and worse, either way.

So…. That’s it! I have given up. The bike rides fine and shifts nicely between 1 and 10 so I’m not that bothered. I hate 12 speed!!

If, at some point in the
future, when I take it to the LBS they say if I’ve done something wrong I’ll update everyone.

Cheers!

R


My mortal enemy!

 

[Fuzz]

Hi all

Thanks for all the replies, but I have given up. It shifts perfectly from the highest gear all the way up to the largest, but going the other way it jumps 2nd and grinds away on 3rd but after that is perfect. As I almost never use these gears that’s the way it’s going to stay until I can get it to the LBS.

I have:

Fitted brand new GX chain
Brand new GX Mech
shortened the cable, checked it isn’t binding anywhere so it fits exactly as shown in mech manual
set barrel tension to four clicks out then tightened the bolt (to the correct torque using a torque wrench)
Checked hanger alignment using an alignment tool. Three times. It’s within a mm across 0, 90, 180 and 270 degrees
Used the correct (white) SRAM Mech alignment tool to check the B screw alignment.
Checked both high and low screws are correct. As the chain goes into top and bottom gears without a problem, I have no reason to think there is a problem with them.
If the barrel adjuster moves from four clicks out things just get worse and worse, either way.

So…. That’s it! I have given up. The bike rides fine and shifts nicely between 1 and 10 so I’m not that bothered. I hate 12 speed!!

If, at some point in the
future, when I take it to the LBS they say if I’ve done something wrong I’ll update everyone.

Cheers!

R

View attachment 53737
My mortal enemy!

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

 

[GMLS]

Embarrassing admission alert : I had exactly the same problem as you and finally noticed that after taking the mech apart to give it a good clean when I changed the chain, I put back the jockey wheels the wrong way around. One has a couple of teeth more than the other, and only realised when I compared against my manual bike. I also just purchased the new SRAM gap tool which also helped setting everything up and its all spot on again.