First the details:-
Deore XT Rear Mech
Deore XT Chain Rings
SLX Front Mech
SLX Shifters
9 Speed Cassette Unknown
Bike: Trek Fuel Ex 8

As implied by title, I am having a problem with ghost shifting or delayed shifting. Rear gears shift without me wanting to or gears don’t shift (until later) when I do.

Thing is I have had it in to LBS twice. When it’s up on the stand, they’ve twiddled and fettled and said:-

“There you go, all works Fine”
“Cool – what was wrong with it?”
“Nothing really, just needed adjusting”
“How much will that be?”
“Nothing, it only takes a minute”
“Cool!! What if it happens again?”
“Should be OK, but just bring it back if it isn’t”

Very nice service – but within “a ride” of having it sorted it starts again. I don’t want to be a burden on my LBS, but I also want to get it fixed.

What advice can you offer?

Are your outers long enough? Watch them as you compress the suspension.

exorcism or ghostbusters

Maybe need to check all the ends of the outers ,you may have a collapsing nipple. Now you don’t want one of those ,do you sir? 😉

Are you on a full sus bike or hardtail?
If hardtail, its unlikely to be outers too short.
If full sus, i’d go for the outers too short.

put on workstand
take out/empty air from rear shock
pedal bike
move swingarm up and down
if it jumps gears you know that you have a suspension based ghoast shift

you can then change the routing or length of gear cable outers to remedy

8speed + SRAM 1:1 rear mech and shifters

In my experience, suspension based ghost shift.

The Outers I assume is the plastic sheathing?

Anyways, there is a short length of sheathing from the rear mech up to the seat stay where it goes into a metal gromet type thingy at which point it’s just bare cable, then back into sheathing at the top of the seat stay. Same thing happens under the top tube.

Which section is likely to be the “Short Outer” causing the problem?

I was also wondering about getting the whole cable sheathed (possibly Gore or something) – but what about metal nipple/gromet things – they are welded to the frame. Also would it even be a solution to do this?

If it is rear suspension related – does that mean there’s nothing I can do about it (i.e. common problem on all rear suspensions?)

Possibly the outer being too short underneath the bottom bracket.

As the suspension compresses the shifter cable gets pulled tighter around the BB as it’s acting as the pivot point, hence the ghost shift.

Definitely a possible as I’ve had the same thing before myself.

Why not just replace the cable anyway? And if it still does it at least it’s one thing you know isn’t causing it.

Hmmmm…. not sure I want to cough up dosh just to find out if it’s the problem or not.

The cable doesn’t go under BB, it runs up the seat stay and under top tube. When suspension compresses, the loop does flex, but I would think it’s supposed to.

What about gear cable going in and out of sheathing? The cable is exposed up the seat stay and under the top tube. There are little rubber boots where it runs in/out of the sheathing which are clipped into metal “eyes” welded to the frame. Is full sheathing an option? Or even desirable?

Thanks for your replies people.

I’ll ask the LBS to look at this and replace if necessary.

Cheers.