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Afternoon, hope someone can help with this:
Out last night on bike with SRAM GX Eagle 12 and couldn't get into gear 1 ie biggest cog. No problem with gears 3-12, gear 2 is very slightly clicky but works OK. But when I go to gear 1 the chain just leaps about everywhere, even jumping 3 or 4 cogs down and not settling anywhere.
Cable tension is OK, limit screws are in the right place. Bike is 3 months old so nothing's worn out, and there's no damage that I know of. The derailleur seems to be shifting properly and is lifting the chain onto the big cog, but the chain is then coming off again somehow.
It was dark so I didn't investigate too closely at the time; I'll get the bike up on the stand at the weekend to have a proper look but I just wondered if anybody had a similar experience and could advise what I should be looking for...? Thanks.
I'd check for a bent hanger first, Eagle's finnicky about everything being just right, but good shifting at one end only is a good sign of a bent hanger, and adjusting anything else if the hanger is bent is a pointless task.
I'm with coatsy.. with 12 spd there is a lot going on in a small space.. the hanger is a good place to start. May be tweeked from transport, hanger screw being a bit off, put against another bike in transport.. anything.
Then if its 3 months old I would be tempted to start from scratch as if it was a new set up.... cable may have stretched and bedded in...
A very small misalignment at the 10 cog, when compunded through to the last 3 may be just enough to have it skipping...
Also - Check for bent tooth upfront.
In order:
1. B-screw adjustment
2. Limit screws
3. Bent hanger
4. Chainset offset (I assume this is OK as the bike is new)
5. Sticky chain link
After that lot, just setup from scratch. Eagle is uber-sensitive to setting so take your time and I'm sure it'll be ok.
Hanger might not be bent; a loose hanger could produce the same issue as the return spring in the derailleur would always try and pull the mech away from that big old sprocket. Good luck.
Bike is 3 months old so nothing’s worn out
But things will have bedded in/stretched/come loose etc
My NX 11sp was very similar to your setup with the additional problem of the smallest cog derailing itself
* cassette slightly loose
* axle slightly loose allowing wheel to move from side-to-side
* too much cable tension
* limit screw adjusted
* hell-pit OE spec chain replaced
I,m also with coatsy, just had same or similar problem with my Eagle GX , local bike Mech put an hanger alignment tool on, yep hanger slightly bent...
Had know problem with the 12 have had with 11 but was the cable stretched everytime.
I'd 2nd checking the mech is tight on the hanger.
I've had similar symptoms a couple of times (albeit on 11-speed) each time the mech had worked loose from the hanger.
Sorted it (I decided it couldn't wait until the weekend). As suggested by one or two of you, the mech was indeed working loose from the hanger - there was quite a gap opening up. Tightened up the bolt and it's fixed.
Thanks for all the suggestions.
I've had a similar issue and had to change the hanger. When refitting the mech it didn't snug up tight to the stop on the hanger, but under tension it's fine. Is that normal?
Had similar with a new bike .
Reset limits and its either spot on at either end but not at the same time. It's 1/4 turn of the barrel adjuster between bag of spanners or nice
I usually put some thread lock on the mech bolt.
Cool that you have sorted it out anyway.