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Discussion Starter · #1 ·
So got a shiny new stumpjumper a couple weeks ago. Gx eagle spec, and ive been riding it hard from the get go =)

Initially, it had no issues with backpedalling even in the 50t cog. And overall worked great.

Fast forward about a week and things go haywire. After a rocky short/fast climb, i stopped for a break before hitting the next climb and as i set off, almost immediately heard sounds from the back that should not be. Stopped within a few feet thankfully, and saw the chain had wrapped itself up between the spokes and cassette.

It wasnt too bad, and didnt even need any tools to free the chain.

Fixed the clearly incorrect position of the limit screws, reindexed, and all was well.

Then backpedal issues started cropping up. Gave it a real good drivetrain cleaning yesterday, reseated the cassette on the wheel, even swapped in a fresh derailleur hanger just for giggles. Backpedal works fine across the range except on the 50t, and its at just two teeth where i can see it catching and dropping down to smaller cogs.

So i guess the question is, is there anything im missing that cpuld be a fix, or did the improper derailleur setup, chain dropping into spokes, and subsequent possible cassette damage screw the pooch?

Id love to have some easy magic fix vs. Having to go back to the bike shop and fight that potential battle.
 

· Out spokin'
In cog? Neato!
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Any chance your rear axle loosened up and backed out a little? This was an ongoing problem with my GF's previous bike. Never heard of it before or since, but for some reason it happened on her old bike regularly.
=sParty
 

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Check that your derailluer hanger is still straight and not bent.

Also be aware that Eagle requires very specific/precise set up of the B tension screw to set the upper pulley + cassette gap.
Sram makes a guide tool for this.
If your bike didn't have the limit screws adjusted properly, highly doubtful the B screw is adjusted properly.
Get that right and providing your chain length is correct and rear d hanger is not bent, the issue should go away.
 

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Discussion Starter · #4 ·
I did a cleaning/detail yesterday on it and the wheels came off for that, and are definitely back on and seated well in the dropouts.

Also readjusted b screw with the guide (ordered one the day i bought the bike since for some reason specialized doesnt include it.) Had a friend help and verified she's spot on in that regard. Although id expect that to affect shifting, but not backpedal drops.

Derailleuer hanger is brand new and didnt make any change. I do have a park tool dag 2.2 en route just because, and its always possible a new one was hosed too, although i doubt it.

When moving/pedalling forward, everything works properly, its just that backpedal/50 combo thats failing. Wouldnt be much of an issue on its own, but ive found that when i stop, its often after a big climb, and im in that gear. If the pedals happen to turn backwards past either of those two spots on the cassette, bam, she drops and the tension from the derailleuer even helps it spin back a bit more.
 

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Chain length correct?

Too short of a chain on a fresh Eagle drivetrain can sometimes do what you are describing.
However, as long as chainline is correct it is rare even if the chain is a link short.
 

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Discussion Starter · #6 ·
Chain length hasnt changed in the two weeks ive owned it, and prior it was set up by specialized/lbs.

Also worked flawlessly until the chain went into the spokes.

That said, i dont have any pics showing it, but in my fairly novice opinion, it looked about right at both extremes of the gear range when i was tuning things back up.

If anything though, id say it may be a link or two longer than needed. But it doesnt stretch out the cages excessively when in the 50
 

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Discussion Starter · #7 ·
Also have a new chain en route (i like having spares) and may try popping it on just to see if that has any effect. Original seems to be flawless and undamaged, and the issue is repeatable based on specific points on the 50t cog, but who knows. German engineering never makes any sense (speaking from the perspective of someone who deals with bmw/audi/porsche/etc. every day.)
 

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If anything though, id say it may be a link or two longer than needed. But it doesnt stretch out the cages excessively when in the 50
That makes a huge difference.
I have the GX Eagle on my Fatty.
With correct B-screw and chain link it schould look like this in the 50T
My drivetrain works great, no chain drop issues at al for at least 500 km.
Bicycle tire Wheel Bicycle wheel rim Mode of transport Bicycle part
 

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Discussion Starter · #9 ·
That makes a huge difference.
I have the GX Eagle on my Fatty.
With correct B-screw and chain link it schould look like this in the 50T
My drivetrain works great, no chain drop issues at al for at least 500 km.
View attachment 1193802
Woot, looks like i did have a drive side pic from before the issue, while in the 50t. Looking at the angle of the chain on the back and bottom sides of the tensioner pulley, i'd say they look pretty close to the same. The angle my pic was taken at doesn't help though.

Bicycle tire Tire Bicycle frame Wheel Bicycle wheel


Also have to account for 150mm of rear squish/chain growth on this one.
 

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Maybe a chain link ist damaged, because of what happened?
If nothing helps I would buy a new one.
This, my eagle was having issues popping in certain gears and I couldn't for the life of me adjust it out. Long story short I ripped teeth out of my cassette (my fault, pedal plus shifting) on my 5th ride with the bike. Lbs replaced chain and cassette under warranty and I haven't had an issue since. I assume it was the chain anyway, not a bet tooth on the cassette... But try a new chain anyway.

This drive train is extremely picky, any little thing can cause issues. When it works its amazing though...
 

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Discussion Starter · #12 ·
This, my eagle was having issues popping in certain gears and I couldn't for the life of me adjust it out. Long story short I ripped teeth out of my cassette (my fault, pedal plus shifting) on my 5th ride with the bike. Lbs replaced chain and cassette under warranty and I haven't had an issue since. I assume it was the chain anyway, not a bet tooth on the cassette... But try a new chain anyway.

This drive train is extremely picky, any little thing can cause issues. When it works its amazing though...
Hopefully the cynic in me is unjustly distrustful of bike shops and they'll at least try to go that route in my case.

Figure I'll take a trip down just to see. I do have another chain landing tomorrow, so that's an option to try as well.

I also thought that briefly though. Like if a link were squeezed and the gap wasn't big enough for the tooth to make it in smoothly then bada bing, issue found. The only thing that made me write it off (well, it could still be one of the issues, just not the only one) is that the drops happen at the exact same two teeth on the 50t cassette. I can reproduce it with 100% consistency when it hits those particular two.

Gotta say, the finicky nature of 12sp is more than I expected it would be. I kinda like it though just because I'm a tech type person anyway and like a good challenge, and the system does indeed work very nicely otherwise =)

The super annoying thing is that the tooth profiles on that 50t are so random in shape and size and width and crap that I wouldn't even be able to guess what any specific tooth SHOULD look like normally, lol.
 

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I’m having similar dramas with my GX system. Worked well to begin with then over time shifting degraded and I ended up with a creaky derailleur. The four pins that hold the hinge parallelogram assembly on the derailleur is the issue. There is so much wear/play there coupled with the leverage of the long cage, this has meant crisp shifting has left the building.
It has been returned to SRAM under warranty, waiting on their response. In the meantime I’ve bought another GX derailleur and unfortunately even after only a couple of rides the wear is apparent in the same place. My initial thinking is the cheap cast part on the GX is simply wearing away around the pin. I think the XO1 derailleur is made of better material on this part so that could be an option to negate this issue.....or try an 11sp
 

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This drive train is extremely picky, any little thing can cause issues. When it works its amazing though...
Any drivetrain regardless of brand or price is picky.
One important thing that's often overlooked is the cable tension.
You can adjust all the screws on your derailleur as much as you want, but if the cable tension isn't right you won't get any good results.
More tension makes the derailleur go further into the spokes when on the biggest gear.
Less tension and your dearilleur goes too much in the chain stay direction on the smallest gear.
Before I even touching any of the screws I always set up the chain length and cable tension.
Than the B-Screw and than the rest.
 

· RAKC Industries
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Not really. Lower speed count sram and shimano I have had 0 problems ever. Even shimano 11s has been just as reliable and easy to set up as 9 and 10s. Both my sram 10s and 11s (both gx) have plenty of mile and 0 issues.

Its 12s, charging ridiculous pricing for inferior performance. They may have done the top of the line version right, but they cheaped out to continue reaping the rewards and riders are now dealing with it. 12s wasnt even a redesign, it was just a new shifter and shiny cassette.

Sent from my SM-G950U using Tapatalk
 

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See post #778 for description and photos of my recent issues associated with sucking sticks into lower jockey, pulling GX12 cage into spokes, twisted derailleur, replacement, etc. Since this post I have not had any issues after multiple rides on debris covered trails but I am paranoid as hell it's gonna happen again. But I got to say...I LOVE the 1X12 other than that.

http://forums.mtbr.com/drivetrain-shifters-derailleurs-cranks/sram-eagle-1x12-1002523.html
 

· West Chester, PA
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I'm having similar dramas with my GX system. Worked well to begin with then over time shifting degraded and I ended up with a creaky derailleur. The four pins that hold the hinge parallelogram assembly on the derailleur is the issue. There is so much wear/play there coupled with the leverage of the long cage, this has meant crisp shifting has left the building.
It has been returned to SRAM under warranty, waiting on their response. In the meantime I've bought another GX derailleur and unfortunately even after only a couple of rides the wear is apparent in the same place. My initial thinking is the cheap cast part on the GX is simply wearing away around the pin. I think the XO1 derailleur is made of better material on this part so that could be an option to negate this issue.....or try an 11sp
My GX RD was creaking as well. I could make it creak just by pressing on it a certain way. Took a video and sent it to the dealer (universal cycles), they said they would inquire with sram and get back to me... they never did.

Now after a few hundred miles the creaking stopped. Shifting is perfect for me but if it gets bad or it breaks I'm just going to buy an 11 rd.
 

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Discussion Starter · #18 ·
Figured the worst that could happen is nothing, so dragged the bike down to the shop yesterday after work. Can only guess that what seemed like a minor crash a few days prior to the issues cropping up may have hit the derailleur, knocking the hanger and whole thing out of whack. Didn't notice any shift issues at the time, but that probably led to the chain into spokes condition later. And for more follow-the-clues fun, that led to bending a tooth or two on the 50t cog.

Long story short, a minute with a derailleur hanger alignment tool, and a pair of pliers for one persistent tooth, and all seems to be well again.

Makes me wonder if the dropouts on the frame are a bit out of whack though since the derailleur hanger that the shop guy quite clearly straightened out was brand new and unused (I had swapped my spare in the other day just to eliminate that possibility until my own DAG-2.2 shows up.)

Anywho, that was a shitload less painful than I was expecting. Also proved to me just how much a GOOD bike shop mechanic's experience works better than me + a shitload of forums/youtube.
 

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Anywho, that was a shitload less painful than I was expecting. Also proved to me just how much a GOOD bike shop mechanic's experience works better than me + a shitload of forums/youtube.
the 2nd reply to this thread suggested to check your rd hanger, most of us me included are too lazy to check hanger alignment on a regular basis, but I can't tell at least for me every time I check it's not perfectly aligned and needs some bending back!
 

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Discussion Starter · #20 ·
the 2nd reply to this thread suggested to check your rd hanger, most of us me included are too lazy to check hanger alignment on a regular basis, but I can't tell at least for me every time I check it's not perfectly aligned and needs some bending back!
While that was part of the fix, it had no bearing on the backpedal issue. It made shifting buttery smooth and silent again, but even with the hanger perfectly straight, that issue persisted until he used pliers to coax an errat tooth on the cog into a better position.

That said, the DAG is gonna get regular use from here on out.
 
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