tandemnh

Rear Derailleur Double Shifting - Shimano - Deore XT - 9 Speed - When I shift up or down the rear derailleur more often than not double shifts causing me to have to reshift to get to the gear we need to be in.

The cable has just under 1000 miles on it, the derailleur is not bent and has not been in a crash, I have been tugging on the cable to take out any slack and have tried different tightness settings...

Has anyone experienced this and how did you fix it?

TandemGeek

If you're positive the rear derailleur hanger isn't bent, I'd be inclined to carefully inspect the derailleur cable housing with an eye towards the cable stops: check to see if the housing is properly and cleanly seated in the ferrules.

I can vividly recall a time when I over-rotated the handlebars and didn't realize that my rear derailleur cable housing pulled out of the ferrule at the downtube cable stop and then ended up sitting on the edge of the ferrule which created all kinds of shifting problems, some of which you are describing.

So, again, if you've verified that your RD is in good shape, the hanger is straight and your shifter wasn't acting up, I'd unbolt the derailleur cable at the RD to loosen up the derailleur housing and check to make sure all the ends are seated properly, have ferrules and that the cable isn't kinked or binding any where in the housing.

pjgonwa

I have thumb shifters on my Trek T100. When I activate the shifter thru it's complete rotation it will double shift. If I only want to single shift I activate only half a rotation. (This action comes in quite handy in the hills)

I have a 2nd thumb shifter to go to the higher gears. Activating this only single shifts.

justcrankn

I'm assuming you have STI shifters. If the cables survive TG's inspection process then I would look at the rear derailleur. You might have misadjusted the cable to accomodate a sloppy worn derailleur. AFAIK the only fix is a new derailleur.

gpelpel

I had the same issue on the used Santana I bought a couple weeks ago. After changing all cables and housings it is working perfectly now.
Even if you only have 1000 miles on the current cables, if water or mud happened to enter the housing your cables may not moved freely at the housing ends. Another issue could be a too short housing that bends the cables too much when turning or when transporting the bike. You could also have dirt in the derailleur mechanism or a weakened spring.

jnbrown

I had a similar problem with the original XTR derailleur. It seemed it had a lot of play in it so I replaced with a new XT and that fixed the problem.

PMK

There can be a few things causing troubles.

The bent derailleur or bent hanger is a consideration, but I'm not so sure you'll get a double shift unless it's really bent a lot.

A worn rear derailleur is viable, and from experience the XT's that were 8 speed versions with the polished aluminum have been more prone to wear and subsequent play / slop. The 9 speed versions which are a satin finish seem to hold up better. You can check these by grabbing the lower cage by the bottom pulley and checking for side play. If (with a straight hanger) while having the system selected in gear 1, check the clearance to the spokes while pushing the cage towards them. I don't know of an actual wear spec, but if it seems to close for my liking I replace the derailleur.

Myself, when I check cables I try not to disconnect the inner wire. My preference first is to select the smallest sprocket on the cassette. Then without using the shifter, move the derailleur by hand while pedaling in the largest cassette sprocket. This normally will allow the housings to be slid free of the frame fittings. This will allow the cable housing to be positioned in some spot mid span and have the end ferrules removed (unless they were swaged) to inspect the housings ends. I find that over time, you'll notice the housing outer sheath will slide back from the cables true end. This normally is the housing failing, flush would be great, a couple of mm's is normally acceptable, after that I believe it's time for replacement. Obviously this does not work for checking the shifter end with taped bars, so the frames end will have to suffice.

With the housing slid back, this is also an easy way to wipe clean portions of the inner wire, and then it can be lubricated before you reposition it onto the frame.

For me, I've typically found shifters are something that works or doesn't. If it will click each gear they normally are ok. Cable housings have given me the most grief, sometimes even when checked as mentioned above, they seem good but still there is a problem, new cables, problem solved. Grit and corrosion can be the other culprit.

If you want to look for a not to common concern, if your frame has the plastic guide under the bottom bracket shells, see if those are intact. Recently on a friends bike the shifting went crazy, similar to this double shift stuff. I installed new cable housings, in the stand it was better, after a quick test ride it failed again. Found the plastic guide had worn through and the cable inner wire was getting caught between it and the frame.

My first pick would be bad cable housings.

FWIW, when I finish a ride, I try to always position the rear onto the smallest sprocket, as this will store the bike with no tension in those cables.

PK

cornucopia72

Last time we had double shifting problems it was a bent RDR hanger. Also, make sure to lubricate the cables as they go around the BB.

Retro Grouch 

Are you sure the cable is attached to the correct side of the anchor bolt?

tandemnh

Thanks for the input. It took a bit of fiddling around but eventually with the help of the wife we were able to reset everything and pull the cable tight, now it is shifting very good.

Thank for everyone's input... success!!!!