Help! - Adjusting Rear Derailleurs - Deore XT to be exact

[Multipass]

Does anybody here know the secret to adjusting these vile little pieces of machinery?

The bike in question is Specialized Stumpjumper FSR XC Pro. I bought it new last week. This evening the rear derailleur has crapped out on me. My first thought is that the cables have stretched-in a bit and need some adjusting. A normal occurrence on a new bike. (I've put 100KM on it so the timing for cable stretch is about right) However, try as I might, it simply will not work properly anymore. I've read the manuals and followed the instructions. No success there. I've tried to figure it on my own, no success there either. This thing worked great until tonight then BAM! - crap shifting.

The derailleur is a 9spd Deore XT. Here's what it's doing:

Upshifts -- kinda OK, not as crisp as it was, but OK. Sometimes it sounds like it's trying to upshift on it's own though. Sometimes, but not always.

Downshifts -- Here's where things have gone right down the crapper. It either:

Hangs up on almost every down shift.

or, after adjusting as per the manual

Hangs up on at least one gear. Adjusting the cable just changes which gear it hangs on.

The high/low stops are fine. It's not pitching the chain off.

No damage or abuse either.

So, what's the secret I'm missing here? Have I missed something obvious?

I'll probably take it back to the shop it came from and let them deal with it. They do have excellent service and after sales follow-up, but I really, really hate not be able to fix something this simple myself.

Thanks in advance guys

-Mp

 

[new_dharma]

if the follow-up is really good they should show you how to do the adjustment for the future...it's part of good customer service (in case the "simple adjustment" is needed in the field).


...and i have no idea hope to adjust it...sorry

 

[fattroy]

OK lets say run it up to like 4th gear on the shifter and the cog too. Look from the back of the bike to see if the der. is inline with that chainring. It sounds to me like its just a adjustment problem. Hope this helps, Troy.

 

[ultraclyde]

I've got a FSR XC Pro, but it's running Sram driveline. My hardtail trek has Deore, though. I second the thought about checking the alignment of the deraileur wheel to the desired cog. Start by bottoming out to the biggest cog and then counting the gear changes up to a mid range gear. If you click thru 4 changes, make sure you are adjusting to that gear. You can watch the cassette as you pedal it (on a repair stand) and see if the chain is trying to ghost shift up or down, and then adjust accordingly.

You might want to check for kinks or tight bends in the cables - if the cable is binding it can cause all kind of shifting issues. Lubing the cables never hurts either.
If you bought the bike new, it's likely cable stretch causing the problem. If you bought it used, it might be cables, or a worn out chain. Worn chains require a lot more deraileur movement to change gears, usually more than you can get and still be in correct adjustment.
If all else fails, buy the LBS mechanic a Starbucks and talk him into showing you how to fix it.

 

[CCR]

always try http://www.howtofixbikes.blogspot.com , not familiar with yours but worked on a shimano i had.

 

[Multipass]

Thanks for all the info guys.

Earlier today I went back to square one - made sure everything was cleaned and lubed. Then re-did the adjustments as per the Shimano instructions (and the other sources linked above).

The end result? It seems to be working well on the stand, we'll see how it does on the trail tomorrow.

The bike is new and includes a year of adjustments and one full tune up in the deal. Bu-u-u-ut the mechanic in me doesn't like having to rely on others though :roll:

Thanks again for the help guys

-Mp

 

[62Higgins]

I learned the hard way that sometimes it is a chain issue.

What I am about to post does not fit your situation from what I can tell, but I thought since people are reading this post that it is worth mentioning.

This happened on a brand new bike too.

I was teaching at a police bike school, a guy takes a brand new Trek police model off the rack on his car, mashes a couple of ham fisted shifts and comes to me saying the thing won't shift right.

I check all the usual things, like cable stretch and limit adjusters and don't really see a problem.

The actual cause came from his P!$$ poor shifting skills. He actually jammed and forced the chain twisting a link or two.

If this is the problem it is easily identified by SLOWLY pedaling (parked and observing the drivetrain, not riding) backwards, the bent link will make it self apparent when it does not quite fit throught the deraileur cage.

When actually riding the bike with this problem, the twisted link jams in the cage before it is forced through. The resistance forces the cage to move, making it shift gears for a second. When the jam clears, the deraileur returns to the proper position.

Please don't ask how long it took me to figure all that out.