Purchased a lovely Ti29'er from the Doncaster company who I will never name again. Since getting it the rear mech has been a total PITA.
When it was delivered it was not indexed at all, throwing the chain into the spokes etc. Put it on a work stand and watched a few youtube videos to eventually get it working. I should say that this is my very first SRAM bit of kit. Shimano all the way usually for me.
First ride and it was jumping in the gears. Another bit of fettling on the workstand and it was ok. Next ride, from the largest sprocket it refuses to move down. Cable goes slack but the mech sticks. Have to bunny hop the bike to get it to move. Last night its lost its index again, threw the chain off the block and into the spokes and again refused to move.
So, is there anything obvious I'm missing ? I'm reasonably competent and have done all the right things.
Any suggestions before I strip it all off, replace it with SLX then video myself smashing it to pieces with a 12lb sledge hammer ?
A rear mech is a rear mech, Shimano or sram, they both work on the same principle, cable operation, the potential weak link in the system.
I'd replace the inner gear cable, check the ends of the outer are ok (no sharp bits to snag the inner cable) or even replace the outer just to be sure, and set the gears up again. Shouldn't cost you more than a fiver to do this.
The fact you say the cable goes slack but the rear mech doesn't move makes me think the inner gear cable is catching on something or encountering enough friction that the spring in the rear mech can't overcome it.
I take it that the rear mech is suitably springy when no cable us attached?
Might be work trying the gears with the rear mech clutch on/off and see if that makes any difference.
No need to strip it out and buy Shimano just yet!
I had an NX mech for the best part of a year and it was pretty poor. Ok initially but the play in the mech got looser and looser. I do think I might have bent it a little too which doesn't help.
Eventually started throwing it into the spokes as you've said, I set the limit screw as best I could, fresh cables etc, but after the second time of going into the spokes and taking two out, I swapped it for a GX and it has been fine ever since.
Without a chain, check if the mech wobbles when you push and pull on it. I had more than a few scratches on mine so couldn't warranty it, but I've had good success with sram warranty in the past.
If still nothing, go for a GX mech.
Sounds to me like your B screw needs to be tweaked in and your limit screws need setting up.
A new cable then a proper set up.
It's mechanical, it doesn't have mood swings or days it hates you and just wants to piss you off.... so check for correct set up etc.... music on and fettle, not a bad way to spend an evening.
If you had to watch youtube vids to set up your rear mech you can probably assume that it's your work that's at fault, and not the kit.
Take it to a shop and pay someone.
He got it from a shop and it wasn't working .
Nothing wrong with watching a video to make sure that you are doing it properly , It certainly doesn't mean that you are incompetent .
If its been thrown into the spokes, its likely you've bent the mech and or the mech hanger...the problems you are now experiencing are probably in part due to that, caused by the poor initial setup, rather than the mech itself being poor,
B screw then check its not unscrewing from the hanger
+2 go back to first principles and remove the mech and chain. Check the hanger by laying a straightedge along it. Any deviation from straight and it’s a new hanger. Check cable pull smoothness by holding the cable tightish in your fingers while operating the shifter. If it’s notchy then investigate the problem. Check the derailleur cage is straight. If it isn’t it probably failed when it overshifted into the spokes. Remount derailleur And manually check limits put the pulleys over the upper and lower cogs but no more. Check the b screw leaves the pickup jockey 1.5 links from the lowest gear. Wind the shifter barrel all the way in then back off three full turns and reattach cable to mech. Check chain sizing and refit.
You should be pretty close to spot on.
As above, for setup purposes SRAM and Shimano are much the same, but a bad initial setup on either can lead to chasing your tail.
@vincienup:
neat !
And yes - you are right - basic set up SRAM and Shimano should be the same.
I really like the Deore 2x10 and when setting up a new drive train: exactly what you describe.
Start setting up rear mech without chain. Upper and lower limit screw, alignment of pulley to cassette... then with chain: fine tuning B screw and selecting chain length - and adjusting shifting quality with help of the (cable-) adjustment screw on the shifter.
No idea if this depends on Shimano / SRAM or setup: chain drop - on my bikes - happens on front mech. Never had a chain dropping on the back mech....(luck?)
Guess important: chain not too long. And this clutch thing on the rear mech has to work...(if the "clutch" is stuck the chain might do silly things as well)
@lowey: don't use the sledge hammer yet... better ask the LBS to fix it!
'I’m reasonably competent and have done all the right things'
Apparently not
So, took your advise and dropped it in at the LBS workshop. I figured I'll just get it sorted once and for all and pay them as I had lost all patience.
They have just called to say there is some fundamental problem which they have never come across with the mech and the distributor want it back to inspect.
Bikes off the road till its sorted.
Only confirmed my hatred of SRAM. I'm gutted that my new FS is coming with it on.
"Apparently not" - Cheers for your help.
Is it a new bike ? if it is they should replace the rear mech with a new one from stock to keep you on the road . Sram Tech will just send the shop a new one after they have looked at it , it's only a sub £30 part after all .
@lowey: too bad to have this trouble. But sounds like all is good soon again!
Yesterday I actually had to think about this post while doing a nice snow mtb tour. Took the bike out of the garage and after 5 miles or so in the forest my rear mech didn't move at all any more. Guess there was some moisture/water still from my Sunday tour in the rear mech (Shimano!) - and this froze the rear mech solid once the bike was in the woods again...haha - had to think right away about your post...no chain drop so. Simply no rear mech gear switch any more...
All is fine again now. Sprayed plenty of thin oil onto the whole unit.
Cheers!