I’ve got a 2016 Santa Cruz Hightower with a 12 speed SRAM GX Eagle drivetrain. When I’m in my lowest gear and push hard on a climb, it will skip several gears. During regular pedaling and in the stand (see video) it seems to work fine. It’s just when I throw it into that low gear to try and grind up a climb.
Is it the derailleur, cassette, both?
Skipping gears when under load
byu/Gringobandito inbikewrench
by Gringobandito
11 Comments
Check the hanger ailgnment
New chain? Could be stretch in which case new cassette time.
Could be hangar alignment but more likely chain and or cassette wear, a close up picture of the smallest cog could help. Get yourself a cassette wear indication tool or replace it and see what happens
It’s hard to know from the video if things are getting warm out. I will say it certainly looks like everything needs cleaning and lubricating. Have you tried playing around with the barrel adjuster? If that doesn’t work, I like to start from step 1, clean and lubricating everything. Then start all over. Move to 12th gear and detention the cable. Set the low limit and work from there to set the high limit, b adjustment, and tune all over again. If you can’t get it dialed from scratch then your system may have too much wear and or a bent hanger. Though, a bent hanger should cause issues across the whole cassette not just one gear, usually.
Looks like stiff links. Try cleaning and lubing the chain. I had a similar problem and ultimately had to change the chain.
More likely the chain. Hanger out of alignment is possible, but it would probably not shift that well in the stand. Hanger issues usually present with only being able to tune one half of the cassette.
But also could be the cassette is also worn.
You will need a chain length tool to confirm the chain wear.
I know it sucks, but I highly recommend chainging the cassette with the chain with SRAM 12s.
Good luck!
I been there, tried everything. One of my problems was bent chainring. Square bb was making it woobble too. Remove the chank and rotated the cranks till one SIDE of the axle was perfect.
This fixed heavy load on Nice roads mostly
Then figured out that when upgraded from 7×3 to 9×2 the chainline was off. Then changed the square bb from 130 to 118mm and now the bike won’t skip anymore on under load over potholes.
B tension set correctly with suspension at sag?
Very important with Eagle. White tool easier to use than red.
The only times I’ve had this symptom , it was worn drivetrain. Replaced chain, chainrings, and cassette and everything became smooth and reliable again.
Seems very strange that the derailleur shifts a few gears down. Seems that would only be possible if the derailleur is somewhat able to wobble. I don’t have 12 speed but haven’t had this in Shimano 11 & 10 speed systems. Has lbs seen it?
Stuck links