help!

Ive just installed a brand new sram GX 12×1 groupset setup on a Ritchtey ascent frame, 68mm BSA, QR dropouts.

I cant for the life of me get it to index from the smallest to next cog, and if I do it throws out all of the other higher gears.

Everything looks ok, but a couple of points:

1.the mech is at full limits for both H & L – so i cant increae the limits either side.
2.The lower limit on the mech pushes the cage against the plastic housing that the roller bearing cable feeds through, to the point where it starts to bend the casge by 1mm. (this is at full lower screw limit).
3.Used the included tool to set B screw
4.kept the cable housing as short and straight as possible
d..the chain doesn’t sit/catch on the biggest 50t cog very well, seems to float on the cogs.
5.left only 1 extra link in the chain overlap when guide is 2 for HT.
6.the smallest cog seems to sit outside of the chain line to the crank (not sure if this is supposed to be like that).
7.Voodoo magic and blood has been spilt as offering to the gods of gear indexing

https://1drv.ms/u/s!Av_8K8wy3-u8kTmARGVm1RWQM-jE?e=yeujyb

I’ve just installed a GX too.
There’s not much room for error in there.
With the mech holder button engaged, it looked like it wouldn’t index but once the chain was fitted and the mech released it was ok.
At one point the outer cable piped out of the mech which introduced some slack. Double check that.
It does feel a little like it’s not quite right still.
I’m going to give it another go in the morning. Will report back.

As for the 50t cog meshing. For me, it feels like narrow/wide. I found slipping the chain one link allowed it to mesh perfectly

Also, I’m putting a bigger chainring on, so I’ve left the chain a little longer than I would. That may not be helping me. I see you’ve accounted for that

Could possibly be that the rear dropout is too thin and adding a pedal washer as a spacer between dropout and rear mech could improve things?
I saw similar on steel inbreds ages ago.

SRAM Spec is hanger should be 8-9mm thick. On a light steel frame it might not be. So use a spacer to move the rear mech across.

When setting mine up we initially had problems. It was a new giant trance frame. Turns out there is more than one mech hanger standard and I had the wrong one sent with the frame. Correct one bought and it was easy to set up after that.

Op, search out a thread I made about a year or so back about setting up the GX Eagle. I had EXACTLY the same issue with the cage hitting the plastic cable guide as you’re picture shows!👍

For the life of me I can’t remember what cured it. I have a feeling that it just became a non issue once the mech was all set up. Something sounds very wrong that both the limit acres are at maximum. That’s odd…

Also get the mech hanger checked.

I bought a tool to do this specifically for setting up my first Eagle upgrade and I have used it many times since. If you don’t want to buy one, get the hanger checked at your lbs.

Persevere mate. Took me a while to get my head around Eagle but now I find it pretty intuitive. An out of whack mech hanger WILL cause issues on Eagle though, the tolerances are small.

If you can index one end of the cassette but not the other, it usually means the derailleur is out of alignment, either the hanger or the derailleur itself. The more gears you have the closer the cog spacing, the closer the cog spacing the smaller the misalignment needs to be to effect indexing.

As Brant said, if the cage hits the guide then the derailleur needs to be spaced further out using a washer.
The floating chain is probably a B-tension issue, but that should be sorted only after fixing the first issue.

I’ve recently 12sp eagle on two new bikes. Both now work like a dream but the first wouldn’t engage the 50T correctly as mentioned above and on many more problem posts all over the net.

I rotated the chain 180 degrees and put it on updside down and it then worked like a charm.
Kept the link the correct orientation as it has a definite radius to it but otherwise I couldn’t see or tell any difference apart from it drops into the 50T easily now and performs very well.

The one I had this problem with was X01 and was bought as a groupset.

I expect Eagle was designed around 142/148 axles, as yours is 135 then spacing out the mech hanger as others have suggested should help if keen to run Eagle on a gravel bike.

I pissed about with mine for a while, kept throwing the chain over the back of the 50T, ended up apply pressure to the cage when setting the hi and lo limits to compensate for the lateral play in the GX derailleur that the screws weren’t picking up at in the initial turns.

+1 for checking the mech hanger alignment and straightening if needed (even if the hanger/frame is new).

Point 2 doesn’t make sense. I don’t see how you can possibly have both limit screws fully in.

The chain won’t mesh on the 50t properly in the workstand, but it will under load so that’s nothing to be concerned about.

Just noticed in the pictures that your b tension looks miles out. Looks as though the screw needs unwinding a fair bit. This will probably help the cable angle into the mech as well.

I’d second the B-tension not being set correctly, the tool is very helpful for setting the distance.

Can’t quite see from your photos but I might know of someone (ahem!) who was unfamiliar with SRAM kit and got the cable routing through the mech slightly wrong (‘they’ missed out the small tunnel/guide before the clamp) which meant that shifting either worked at one end of the cassette or the other but not both.

Thanks for all the help people!

What i mean by the limit screws is that they are fully open, and screwed all the way out so there is no way for me to extend the mech further on either H/L limits.

@brant the washer could be the answer here! Hopefully a mm to the right will sort it out.

Thanks for spotting the B tension I will take another look at it, I’ll check this first before adding the washer inbetween the mech and hanger.

I’ll also give the chain flip a go, but cant remember if I have a link removal tool.

I think I’ve routed the cable around the pulley and the small hole that exits out to the clamp.

I’ll take a look for that thread @poopscoop – thanks!

In hindsight I should have gone for an 11 sp gravel setup Rival/XX mix

Ok, just noticed the crank needs to be tightened to 54Nm. I only did 8Nm as thats what I saw on the bolt.

Finally found a manual (not easy to find!) and found out the correct adjustment. Another thing for me to sort out and retest.

https://www.sram.com/globalassets/document-hierarchy/user-manuals/sram-mtb/drivetrain/95-6118-019-000-rev-d-dub-mtb-cranksets-and-bottom-brackets.pdf

And this one for MTB frame tolerances for compatibility, this is where it goes into detail about hanger width for QR and min chainline, etc. Very detailed document.

https://www.sram.com/globalassets/document-hierarchy/frame-fit-specifications/mtb/frame-fit-specifications-2019-mtb-components-rev-c.pdf

OP, as others have said check the mech hanger is straight first.

@granny_ring – I’ll do what I can first, thanks. It’s a new frame so I’d be surprised if it is bent.

Also the suggestions are all valid regardless of whether the hanger is straight or not.

SRAM minimum hanger width is 8mm. My hanger is 6mm. So even if the hanger is bent, I’ll still need to add at a mm or so before it’s closer to SRAM spec.

When I have access to a hanger alignment tool I’ll get it checked but for now I’ll make checks on the good suggestions that people have provided.

@granny_ring – I’ll do what I can first, thanks. It’s a new frame so I’d be surprised if it is bent.

I’d be surprised if it wasn’t 😉

Just been for my first ride on the GX. It’s the worst gear system I’ve ever used for losing index. It would be absolutely fine, then it would start ticking. I’d change gear up and down and it would be fine again for a few minutes. Then it starts ticking again. Drove me round the twist.
I’m going to take it all off. Start with checking the absolutely brand new mech hanger for straightness and try again. Eurghhh
In the bike stand it’s perfect

Just been for my first ride on the GX. It’s the worst gear system I’ve ever used for losing index. It would be absolutely fine, then it would start ticking. I’d change gear up and down and it would be fine again for a few minutes. Then it starts ticking again. Drove me round the twist.
I’m going to take it all off. Start with checking the absolutely brand new mech hanger for straightness and try again. Eurghhh
In the bike stand it’s perfect

Complete opposite to my experience, 30 miles in. First couple miles in, I had a to put half a turn on the barrel adjuster as it was catching ever so slightly in the lower gears, perfect now. GX mech and shifter, XX1 chain, X01 cassette.

FS or hardtail? Don’t forget that the b-tension needs to be set in the sagged position if it’s a FS.

I’ll do what I can first, thanks. It’s a new frame so I’d be surprised if it is bent.

How do you spell assume? 😂

100% bent hanger. They don’t come straight from new. Get it checked

ivorhogseye

Subscriber
Just been for my first ride on the GX. It’s the worst gear system I’ve ever used for losing index.

Keep at it mate. It simply shouldn’t be like that.

I’ve set up GX and NX and once dialled in they have been fit and forget for me. I did buy a cheap mech hanger tool though which I use on new frames or second hand. A new frame is no guarantee of alignment, I’ve found anyway.

Thanks both. I’m hoping it’s the b screw not being set with sag. I’ll have a go of that later. Will be great if it’s that

So, i’m not sure what crack I was smoking but I did something wrong when setting up!

First thing i sorted was the crank and got the correct torque set from 8Nm to 54Nm as per manual, then set the bearing tension with the little adjuster.

Second job was to check the B tension. So to be sure I removed the mech, reset the b tension to the middle and remounted, straight away I was able to set the correct limits with room to spare (over extend on both H/L) which I couldn’t for the life of me set before.

From here it was plain sailing, set the correct limits on the mech, checked the B tension with the tool and got the cogs to match 100%, then tensioned the cable then turned the crank, indexed every gear first time.

So I’m 99% sure B tension was the culpirt, although there may be chance that I had just mounted the mech wrong as I’ve never seen H/L limits unable to over extend before.

Took the bike out for a test ride and the shifting was way better than I expected, while turning the cranks indoors on the stand it felt stiff and clunky but once on the rode it was smooth as!

Thanks for all the tips and advice!

@fakiee

There is a dark art to setting up 12 speed but once you’ve mastered it, its fairly easy.

The first thing I would say is try and follow this video as close as you can. Follow the procedure in the same steps they do. (I appreciate you’re on a hard tale so some of it doesn’t apply and you might not be installing all the kit but the steps for the mech’ etc. are all in there. It should be easier on a hard tale because there’s no sag point at which you need to set the b-screw, the difference is that big on a full sus’ that you can get it perfect in the stand but when you take it on the trail you find its like a bag of spanners).

Some important points, and apologies in advance if this sounds like grandma sucking eggs…
1. Plenty of lube on your mech cable so it doesn’t stick anywhere in the cable outer.
2. Watch your cable clamp or internal routing to make sure there is nothing restricting the cable movement.
3. Two full turns of your barrel adjuster clockwise form the slackest setting (fully anti clockwise) before you clamp your mech cable in the mech.
4. Adjust your lower limit screw BEFORE you clamp your cable so that the top jockey wheel lines through with the outer face of the smallest cog of your cassette.
5. Pull the cable quite taught and clamp but don’t pull it too tight. If you test it by shifting up at this point and the mech moves but it doesn’t shift up the cable isn’t tight enough. if it starts skipping up without shifting it’s too tight.
6. Make sure the chain is short enough, it doesn’t like slack chains.
7. Make sure you pre-stretch your cable by dry shifting all the way up without turning the cranks (if you’ve put your chain on at this point) and pushing hard. Do this 5 or 6 times, unclamp the cable move the cable back and forth a bit and then repeat 5.
8. Set the upper limit screw so that by coming back just half a turn on the upper limit screw from the point where the chain goes over the cassette.
9. As you’re on a hard tail you may want to set your b-screw before you set your upper limit screw because you don’t have to faff with the suspension sag and the b-screw does affect the alignment of the mech. I always put a little more b-screw on so that the line on gauge is a little further into the tooth well. I can see from your photos that there isn’t enough b-screw, that’s why the chain is riding off the cassette cog, think of it as an adjustment of how much the chain hugs the cassette.
10. Test ride and any fine adjustments or ticking in any of the gears should be resolved with half a turn either way with the barrel adjuster.

If you do need to adjust the lower limit screw again because it’s not dropping into the bottom cog after doing all the above, make sure you up-clamp the cable first. The mech won’t move over by even a small amount if it’s being held by the cable. You have to re-clamp the cable after it’s happy that it’s sat on the bottom cog.

Hope that makes sense… again apologies if any of it’s a bit obvious and good luck.

Cheers

Took the bike out for a test ride and the shifting was way better than I expected, while turning the cranks indoors on the stand it felt stiff and clunky but once on the rode it was smooth as!

FFS…. could you not have struggled for just a little while longer to vindicate my typing out of my own 12 speed installation manual !!!

B screw seemed to work for me too. Won’t run in 12th in the stand but works out of the stand.
Thanks op for posting and everyone for the tips. Thanks excitable for the essay 🙂

@excitable oh sht sorry dude, haha! But at least you will save countless other people hours of trial and error! I’m a few pints in tonight but will check out your post when my eye are less blurry to see if there any tweaks I can apply to get it crisper, thanks for the tips! 🙂