Rear mech throwing chain

funkyjebus

I recently changed the cable on my rear mech and have not been able to get shifting right since, I've never had any issues before. I have attached some pics for reference.

Essentially, I can only get the shifting smooth for when I'm in either the small chainring or the large, but not both. In the pictures, the shifting when on the large CR is fine, but once I go down to the small CR (in my highest rear gear), the chain slips off between the cassette and the wheel. I have attached a picture of the cassette and rear mech when in both CR's.

As you can see the when in the large CR, all is fine and seems inline and shifting is perfect. In the second picture, I have just shifted to my small CR and have made about a half revolution with the cranks, from the pic it is clear that the rear mech is pulling in too much (the cage is hitting the spokes!), but I have let out the limit screw as much as possible, but still no change.

Anybody got any ideas, I messed around for more than an hour on this, which is too long for a pit of fine tuning and had to stop for fear of 2 wheeled domestic violence.

Thanks

CheGuedara

Assuming there's no obvious damage/twisting to the derailleur I'd just go about setting up the RD again (won't take too long at all).

First take the wheel off and make sure the derailleur hanger is tightened up as it should be, then make sure the derailleur is bolted up to the hanger as it should be (simple things but have seen them loose and affecting shifting on bikes before).

Then put the wheel back on and release the RD cable. Shift the chain to the small ring front and manually put it to the big cog rear combination and adjust the low (L) limit screw so that over travelling (into the spokes) does not occur. Then shift to the big front ring and allow the RD to give you the small cog rear combination and if necessary adjust the high (H) limit to ensure the chain is not dropping into the frame - as you don't mention issues at this end of the cassette you may not have to do anything.

Now you should have the derailleur set up in such a way that the limits are set so that over and under travel is not possible after that it's just a simple matter of tightening up the RD cable, taking out slack in it if necessary and it should all be hunky dory.

There are a multitude of other derailleur tuning info sources out there and the way that the job is done can be sightly different across them. This method has worked well for me - for everything else there's always Sheldon or Wiki

ashleey

My best advice is to start again and follow the park tools website instructions. It has always helped me

Paul Kiernan

funkyjebus wrote: »

but I have let out the limit screw as much as possible, but still no change.

Shouldn't you be tightening the limit screw, not letting it out?

cdaly_

funkyjebus wrote: »

but I have let out the limit screw as much as possible, but still no change.

You should be screwing the limit screw in, not out. Screw it in enough that you can't get to the big sprocket. Then let it out just enough to get the sprocket...

vertigo1976

Paul Kiernan wrote: »

Shouldn't you be tightening the limit screw, not letting it out?

+1

To me it just looks like you need to reset the limits. Follow the steps that @Cheguedara outlined and you should be good to go.

bcmf

As above. Unbolt your cable and start again from scratch.
Set the limit screws while the cable is unattached at least you then know your limit screws arent the problem.
Also make sure your shifter is set to the smallest sprocket (12 or 11 tooth) before attaching the cable. Getting this wrong will throw your shifting out a mile.

funkyjebus

Thanks for all the replies folks. I thought I had tried the limit screw all the way in, but it was late and I was tired. Ill have another go tonight and ill start from scratch.

Thanks again