Rear Indexing keeps going out after about 10-20 miles

Wamas

I knocked my good bike over in the garage and the rear mech hanger must have bent slightly, as the shifting was out where previously it had been perfect. I bent the mech hanger back, and reindexed the gears so they all shifted perfectly, then after some steep uphills where I had to put a bit of effort in, the shifting all went out again (on about 3 of the cassette rings on the back 6,7,8). I have tried this about 3 times, each time reindexing to make it shift perfect in all gears on the flat.

I took the bike back to the shop for its free service, and they indexed the gears again perfect, but on the way out, the shifting goes out again (different 3 cassette rings 2,3,4).

I have checked the mech is not loose, and it looks fairly straight.

Any ideas? I plan on taking it back to the shop, as they said if things were not right to bring it back. If it helps, it is a SRAM rival shifter and rear mech. Oh, and the chain and cassette are fine, the bike has only done about 300 miles.

ds1964

As the hanger has been bent I'd change it; if it fails it will cause a lot of damage and may cause you to come off as well.

andyrr

Could be the hanger is still not 100% straight or even cracked. Also the frame could have been bent slightly or the mech itself damaged also, mayeb try to get these all checked out.

cooldad

Mech hanger is intended to bend to prevent frame damage. They are virtually impossible to straighten - replace it as a first step and see.
Presume you took it off to try straighten it, and didn't just twist the mech?

4kicks

Ive got SRAM Rival and my biggest, perhaps only criticism is that the rear mech seems to go out of shifting, especially in the middle gears of the cassette. Its done it on two cassettes and chains, and can be fixed with a quick tweak of the barrell, but seems to happen much more than good old Campagnolo record 2006 I had before.

marin_maniac

4kicks wrote:

Ive got SRAM Rival and my biggest, perhaps only criticism is that the rear mech seems to go out of shifting, especially in the middle gears of the cassette. Its done it on two cassettes and chains, and can be fixed with a quick tweak of the barrell, but seems to happen much more than good old Campagnolo record 2006 I had before.

I've got the same, and I haven't had to touch the indexing on mine

Monty Dog

If the indexing is continually going out, then suggest that either your cables are at fault or the rear mech is going out of alignment. Get you LBS to check the alignment of the hanger and adjust / replace as necessary. Wrapping your rear mech around your rear wheel can be expensive - I've seen snapped frames and trashed wheels as a consequence of the mech hitting the spokes.

4kicks

Sorry to threadjack, but I really cant work out why my chain jumps
It only happens on sprockets 6, 7 and 8. Ive changed cables (once outers as well to Yokozumas), and Im now runnign a newish Dura Ace chain & Cassette with Rival RD. RD alignement SEEMS fine although Ive not run the park tool over it..I have Rotor chainrings, and the last time I took it to a bike shop (in France) they said it was because my chainrings were twisted - they are not -perhaps the French didnt realise Rotor chainrings are eccentric so at first glance the discs do look twisted!

ANy ideas?- not a limit screw issue as 1st/10th gears are always fine...I can fix it with the barrell adjuster but it then goes again, and typically I can fix it for the big ring but it still happens with the small ring, or vice versa,,,,

Hugh A

I'm sure you will have checked this, but is the cable holding clamp firmly done up? The cable slipping slightly would produce exactly these symptoms.

The thing that makes my gears not index properly is usually lack of cleaning :oops: Nothing throws them out like a bit of dirt - but it does not sound like you will have that problem.

4kicks

Actually it is much worse when dirty, so Ive given it a good clean.
Will check cable clamp..good idea, thanks

keef66

Is the mech hanger still firmly screwed on to the frame?

ride_whenever

is the cable on the right side of the pinch bolt?

4kicks

Yes, and I believe so, will check the SRAM manual again but given it was installed by the shop here in Spain who work for Caisse DÉpargne´s team, doubt they would have put it in the wrong way round. Didnt jump today, actually. Maybe SRAMs designed to work well only in temperatures above 35 degrees c??

satanas

It's probably not the case, but it might be worth checking::
1. the outer casing isn't starting to split somewhere; usually the plastic outer will come away in chunks before this happens
2. if the outer casing isn't cut neatly, some of the strands can make their way through the hole in the outer cap, and this usually worsens over time, both increasing friction and "shortening" the casing slightly
3. the inner cable isn't fraying near the nipple (inside the lever). The latter isn't totally uncommon on bikes with Shimano's STI levers that have done high mileage, and it's annoying and time-consuming to get the remains of the cable out of the lever, especially if it snaps. Better to replace the inner wire if in doubt
4. the casing end caps are not split - only possible if they're plastic

Re the OP's question: If the indexing needed adjusting after the hanger was straightened then the hanger is either still bent, or is now permanently deformed - or the mech is. The other potential problem might be if the cable was undone at the anchor bolt when you adjusted things - it often takes a while for things to settle in again after this is done, but adjustments should only need to be small.