rear derailleur not shifting down

qclabrat

Well-Known Member
I've been riding an XO type 2 medium cage setup for the past few months. It's mated to a sunrace 40t cassette. Today while heading up the orange switchbacks at Chimney I over shifted too low and wasn't able to shift down to a higher gear. I figured it got hung up on the 40 cog as the tolerances were pretty tight to begin with. So I get off my bike and manually bring the gears down. Jump back on bike and hear a grinding sound, which is never good with anything mechanical. For the next 20 minutes I fiddle with the barrel adjuster and cable but to no avail. It actually is only allowing me to shift on the two highest gears. Any lower and I hear the grinding noise and cannot shift down. Also back pedaling creates a lot of chain slap.

upon closer inspection, it appears to be putting too much tension from the pulleys on to the chain and cassette. This is my first type 2 derailleur and I know there's a lot more tension to begin with. I don't think the lock button has anything to do with it and I'm completely stuck with what to do next. It's a 1x10 setup with oneup oval chain ring if it matters.

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I've been riding an XO type 2 medium cage setup for the past few months. It's mated to a sunrace 40t cassette. Today while heading up the orange switchbacks at Chimney I over shifted too low and wasn't able to shift down to a higher gear. I figured it got hung up on the 40 cog as the tolerances were pretty tight to begin with. So I get off my bike and manually bring the gears down. Jump back on bike and hear a grinding sound, which is never good with anything mechanical. For the next 20 minutes I fiddle with the barrel adjuster and cable but to no avail. It actually is only allowing me to shift on the two highest gears. Any lower and I hear the grinding noise and cannot shift down. Also back pedaling creates a lot of chain slap.

upon closer inspection, it appears to be putting too much tension from the pulleys on to the chain and cassette. This is my first type 2 derailleur and I know there's a lot more tension to begin with. I don't think the lock button has anything to do with it and I'm completely stuck with what to do next. It's a 1x10 setup with oneup oval chain ring if it matters.

View attachment 52311
View attachment 52312

The RD position looks really off for that part of the cassette. If you hadn't been riding it I'd think the chain was too long... But I don't think that's it. Could the B screw have popped over/past the stop on the Hanger? It just doesn't seem to have enough rearward tension.
 
The RD position looks really off for that part of the cassette. If you hadn't been riding it I'd think the chain was too long... But I don't think that's it. Could the B screw have popped over/past the stop on the Hanger? It just doesn't seem to have enough rearward tension.
I concur. I had a derailleur similarity implode. It snagged during a shift, and the B screw got yanked out of alignment. If the same happened here then the screw is likely running down the side of the stop. Mine broke the plastic bit and stripped the B thread. Hopefully this isn't the same, because I didn't have much of a successful fix option besides replacing the derailleur.
 
I think you got it right, looks like the b screw snapped off
are they easy to order or should I just go to a LBS for a replacement
 
I think you got it right, looks like the b screw snapped off
are they easy to order or should I just go to a LBS for a replacement
Forget the size exactly, but pretty sure you could get a similar metric screw from the hardware store. Think when I looked for one it was a hex head m4 or something. That's on a GX derailleur. You'll still want to make sure it runs straight to the stop. Since it's just a thin piece of metal the screw can ride down the side and bend if it isn't lined up.
 
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