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Discussion Starter · #1 ·
I have an older bike that originally came with a 3x7 and was upgraded to a 2x9, I have since upgraded it to a 1x12 using the sram eagle NX kit (11-52t, NX 30t chain ring, eagle NX cranks and sram dub bb).

I’ve watched a ton of videos and read a bunch of how to’s to get it mostly tuned. I took it out today for its first ride and have a couple of issues that I’m not sure how to proceed.

I can get it into the lowest gear (largest cog) and it will shift into the highest gear (smallest cog), however when on the smallest cog the chain tends to slip. Going to the next smallest cog and everything is fine.

When shifting on to the last two largest cogs before the 50t, it constantly skips and is pretty much unusable.

What’s going on? Where should I start? Could chain length affect this (I adjusted it using srams directions). Do I need to look at the chain line (I know nothing about this aspect of bike tuning)?

Thanks
 

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Discussion Starter · #4 ·
I want to add one more thing that may or may not be relevant. I was watching a video where a bike shop tech was installing a 1x12 gx setup. To adjust the b tension screw he needed the rider to sit on the bike to get the proper sag. When I did it I read that the rear shock needed to be completely compressed and that's what I did. I don't know if that matters but I thought I'd throw that out there.
 

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I've got Shimano drivetrains so I probably can't help you but I can tell you from experience with my 12-speed system plus from reading many posts on these forums from SRAM 12-speed users that chain length and B-tension adjustments are finicky and critical for either brand. I'm not sure about completely sagging the shock -- have you tried adjusting the system without compressing the shock to see if it shifts better with the shock pumped up? FWIW I did not compress the shock on mine when setting it up. Good luck.
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You don't want the shock completely compressed, you want the shock compressed to sag. If it's slipping in the smallest cog and everything is new, my guess is your chain is too long. Shoot us a pic of the drivetrain in the derailleur/cog area on the smallest cog.

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Discussion Starter · #10 ·
I haven't seen that second video yet and it seems to be very detailed compared to what I've seen before. I'll redo the tuning according to that video and see where I'm at.


Whalenard, what do you mean and how would I fix that?
 

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Whalenard, what do you mean and how would I fix that?
You would fix it by removing a link from your chain. I'm not comfortable advising you to do that to a brand new chain at this point so wait for some more opinions. However given you said that it slips and looking at your pic I'm going to guess that ultimately you're at least one link to long.

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I don't suggest removing a link just yet either but based on the photos, it looks like your B screw is pretty close. Not perfect but close enough. That would lead me to believe there isn't enough tension on the derailleur. Shortening the chain would provide more tension in this case.
 

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I want to add one more thing that may or may not be relevant. I was watching a video where a bike shop tech was installing a 1x12 gx setup. To adjust the b tension screw he needed the rider to sit on the bike to get the proper sag. When I did it I read that the rear shock needed to be completely compressed and that's what I did. I don't know if that matters but I thought I'd throw that out there.
Shock should not be fully compressed. B- tension needs to be set at the sag point (neutral). You need two people (some one to sit on it during set up) or depressurize the shock and carefully add pressure to sag point and then set b-tension. Also, check your 52mm offset and chain length.
 

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Is your hanger straight? On my last bike i upgraded from 1x9 that was shifting perfectly to a 1x11 and couldnt get it to shift without jumps somewhere. I finally took it to a lbs and the hanger was bent. They straightened it and BAM it was perfect. I assumed it was straight since the old system shifted perfectly but dont assume that.
 

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1st step of installing a 1x12 system is to align the derailleur hanger. Slightly out of alignment hangers that work with 8-9 speed systems cause all sorts of issues with 12 speed systems and you will get some of the symptoms you mention with ghost shifting.
 

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I want to add one more thing that may or may not be relevant. I was watching a video where a bike shop tech was installing a 1x12 gx setup. To adjust the b tension screw he needed the rider to sit on the bike to get the proper sag. When I did it I read that the rear shock needed to be completely compressed and that's what I did. I don't know if that matters but I thought I'd throw that out there.
There are 2 rooms of thought. Compressed with the weight of a rider and compressed with the air completely out of the shock. I've done both and it comes down to the bike IME.

Also, keep in mind that chain wrap is premium when using the 10t cog. Make sure you're not trying to put silly power down in the 10t or it can slip under load.

IME, the only time I'm in the smallest cog is when I'm cruising on flat ground. And even then I'm not putting down climbing power.

You would fix it by removing a link from your chain. I'm not comfortable advising you to do that to a brand new chain at this point so wait for some more opinions. However given you said that it slips and looking at your pic I'm going to guess that ultimately you're at least one link to long.

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I agree. 1 link needs to be removed. The chain looks to be almost hitting the derailleur body when in the smallest gear and has minimal tension.
 

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Absolute worst case you can throw a quick link in the chain if it ends up too short after taking one link out (though it doesn't sound like it is). Some disagree, but others have been running 4 quick links just fine for good bit of time.
 

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Absolute worst case you can throw a quick link in the chain if it ends up too short after taking one link out (though it doesn't sound like it is). Some disagree, but others have been running 4 quick links just fine for good bit of time.
I've seen chains with 2 or 3 quick links on them. I've even ran 2 quick links for almost 8 months without issue. The problem is when you start removing quick links that are classified as one use only. That's where quick links can fail.
 

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Discussion Starter · #20 ·
So I followed the second park video and I can’t quite get through the high limit adjustment. It shifts fine in all the high gears without nose but when I get to the last three largest cogs any adjustment I do then causes issues with the smallest cog. When I get to the third largest cog it has trouble getting into it so I make adjustments at the barrel adjuster on the shifter. Then if I shift to the higher gears it will either make noise or not shift all the way down.

I can make it so I can shift into the top and bottom gears but it will have issues starting in the 10/11 (larger cogs) gears.

Once you remove a link from a chain is the only option to lengthen it to use quick links?
 
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