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A bit miffed here - my Shimano XT rear derailurer (new) has started to ghost shift. Specifically, it'll drop to the smallest (lower numerically) cog when I hit a bump (hard tail). This happens often but not constantly and not on large bumps... I'm an XC guy - no big hits ;)

What makes this odd, is that otherwise, the rear and front derailures are shifting perfectly - no rattle/chatter, no dragging, no hesitation, etc. Just smooth, crisp shifts. I hate to start messing with the tension.

Is the chain loose? Is it hopping because of this? Drop two links? Or is it in the tension - back off bit?

Drivetrain:
F: Shimano LX
R: Shimano XT
Chain: Sram
Cassette: Shimano LX

Thoughts?
 

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OldZaskar said:
A bit miffed here - my Shimano XT rear derailurer (new) has started to ghost shift. Specifically, it'll drop to the smallest (lower numerically) cog when I hit a bump (hard tail). This happens often but not constantly and not on large bumps... I'm an XC guy - no big hits ;)

What makes this odd, is that otherwise, the rear and front derailures are shifting perfectly - no rattle/chatter, no dragging, no hesitation, etc. Just smooth, crisp shifts. I hate to start messing with the tension.

Is the chain loose? Is it hopping because of this? Drop two links? Or is it in the tension - back off bit?

Drivetrain:
F: Shimano LX
R: Shimano XT
Chain: Sram
Cassette: Shimano LX

Thoughts?
Check the B tension Spring to make sure the chain is tight enough.
 

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Bent hanger is what I'd check first.
 

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I Have Cookies
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I second the hanger, also bad hub......(loose)
 

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Try 1/4 turn out (unscrewing, increasing housing length) on the rear shifter's cable adjuster. if still a problem then another 1/4 more out. If this adjustment causes skipping or won't shift down easily into the next smaller cog then this is too much adjustment, then go back to where it was, you my have another issue.

Be sure your cable housings are not older than 1 year of frequent riding or they could be very worn inside and pinching the cables and causing irregular shifting effects.

Good luck!
 

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is the rear a shadow?

dan0 said:
is the rear a shadow?
What's up with the Shadow Dan0? I have a shadow - my drivetrain has been doing this for a couple weeks, hanger is fine, as is chain, cassette, hub... I've been suspecting it's the derailleur...
 

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Rollin'in'Zona said:
What's up with the Shadow Dan0? I have a shadow - my drivetrain has been doing this for a couple weeks, hanger is fine, as is chain, cassette, hub... I've been suspecting it's the derailleur...
Nothing's up with shadow, shadow wouldn't cause this problem. Did you check your hanger with a hanger alignment gauge? With the power of my e-speculation, I would say your problem stems from needing new shift cable and housing if the hanger truly is straight.
 

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I have had this happen on my FS when the middle length of housing is too short. It could also be grubby cables/housing.
 

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Rollin'in'Zona said:
What's up with the Shadow Dan0? I have a shadow - my drivetrain has been doing this for a couple weeks, hanger is fine, as is chain, cassette, hub... I've been suspecting it's the derailleur...
the cable on the shadow needs to be about 1/2" longer than you think, even though you get rid of the loop of cable you still need a bit of slack. Its more noticeable on bikes with rear suspension but I've seen it happen on hardtails too
 

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zebrahum said:
Nothing's up with shadow, shadow wouldn't cause this problem. Did you check your hanger with a hanger alignment gauge? With the power of my e-speculation, I would say your problem stems from needing new shift cable and housing if the hanger truly is straight.
e speculation or not if the rear cable on the shadow is too tight(short) it will shift on rough terrain
 

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dan0 said:
the cable on the shadow needs to be about 1/2" longer than you think, even though you get rid of the loop of cable you still need a bit of slack. Its more noticeable on bikes with rear suspension but I've seen it happen on hardtails too
I run full-length housing, and it's on the longish side.
 

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zebrahum said:
Nothing's up with shadow, shadow wouldn't cause this problem. Did you check your hanger with a hanger alignment gauge? With the power of my e-speculation, I would say your problem stems from needing new shift cable and housing if the hanger truly is straight.
Yeah, the hanger is straight (I have more Park tools than the LBS).

I run full-length housing on this bike, and other than the derailleur, the housing is the only component that hasn't been replaced in the past few months.
 

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Try changing out your cables and housing. Full length housing can be good for keeping grub out, but it can also be good for keeping grub in.
 
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