Rear Derailler Problem

[mmcnay]

Hello,
This is my first proper post. Love this site. So useful.

I learned to index my deraillers using the Park Tool videos. Very good resource. My old bike has great gear changes which are slick and lovely. XT derailler with Deore shifters. My new (to me) bike has Veloce shifters and a campag derailler. It will shift into the small cogs with ease. But, going up to the bigger cogs it sometimes doesn't move, but rattles as if it wants to. Then I click again and it goes up two. And then I click it down into the smaller cog. After that procedure I am in the right gear, and it is fine. This problem is intermittent. Sometimes it moves up and down lovely. But often it doesn't.

The cables are fairly new. The shifters work ok on my old bike.

Any ideas?

Do I need a new derailler etc? Or is my indexing not as good as I think?

Thanks for taking the time to read,
Mark

[cycleruk]

If, as you say, it works fine sometimes then I would start with making sure that the hanger alignment is correct.
https://www.parktool.com/blog/repair-he ... -alignment

Look from the rear and the mech' should be parallel to the sprockets.
The same when looking down from above.

[georgew]

Once you have checked the hanger alignment I would then turn the cable adjustment (at end of cable leading into rear der) a quarter turn anti-clockwise which tightens the cable slightly. The correct adjustment of this should mean that the chain climbs smoothly up the larger cogs and drop smoothly down to the smaller when changing gear. If the chain hesitates before moving from large to small then the cable is too tight.

[peetee]

Sounds like the shift is creating a bit of cable compression. Or taking up some slack due to a untightened component. Check the gear mech hanger bolts (not usually found on steel frames). Derailleur mounting bolt, and , if you have a work stand or helpful mate, take a good hard look at the cable route and change gear a few times and see if the cable outer settles in to a frame stop or moves laterally as you shift. This indicates poorly fitted or excessively long cables.

[tykeboy2003]

Here are my 2 alternatives

1 bent hanger.
2 worn main pivot on the derailleur (see picture) check for any sideways play.

[Stradageek]

Most of my obscure indexing issues have turned out to be excess cable friction, even with apparently clean, unrusted inners and outers.

Once I've eliminated the other candidates (posts above) I'd try changing the cable and outers, or at least cleaning and re-lubing them

Also bear in mind that a negelcted mis-indexed shifter (I've ridden past many, many people who seem to be able to ignore the rattle of a chain that hasn't shifted) will wear away the ramps and pins on a cassette to a point where changing becomes very difficult

[Brucey]

one sneaky place for cable friction is in a worn BB guide. This can drive you nuts if the cable drags in it, e.g. because there is a groove worn in it.

cheers

[Mick F]

Here are my 2 alternatives

1 bent hanger.
2 worn main pivot on the derailleur (see picture) check for any sideways play.

shimano-rd5701-black.jpg

I'll bet it's No 2.
I've got through two rear mechs like that on two different bikes. One a Campag Chorus and the other a Shimano Tiagra. Therefore, I know the symptoms and they are just like the OP.

Backlash.

[tykeboy2003]

I'll bet it's No 2.
I've got through two rear mechs like that on two different bikes. One a Campag Chorus and the other a Shimano Tiagra. Therefore, I know the symptoms and they are just like the OP.

Only got through one that way - on a brand new bike only a couple of years old having done about 5,000 miles. I wasn't best pleased. As you say the symptoms were exactly as described.

[cycleruk]

Because the OP says that it is going to the larger sprocket that gives problems but goes back to the smaller sprockets fine, I discounted cable friction initially. I would also just check the cable adjuster to see if a slight turn (to tighten) helps.

[mmcnay]

Thanks for all your helpful replies. I've just gone out and pulled it about, and it does have a bit of play. I'll now research repairing, or getting a new one.
Cheers!

[Brucey]

all these things add up; there isn't a bike out there with cables that are as good as when they were installed, or with mechs that are completely free of play.

BTW the BB cable guide can manifest symptoms as described if increased cable tension pulls the cable into a groove. This is more likely to happen with a new cable than a used one, because a new cable may be very slightly fatter than the cable that made the groove. Also the binding will vary with the weather, e.g. depending on whether the groove is wet or not.

Often the top pulley in the rear mech is badly worn and that is the thing that puts the kybosh on good shifting. Another possibility is that the top pivot is partially seized; this will cause the distance of the top pulley to the sprockets to vary in a non-trivial fashion and with it the shifting performance.

cheers

[531colin]

In the case of poor shifting, the first three things to check are.....
the cable
the cable
and the cable

[thirdcrank]

Here are my 2 alternatives

1 bent hanger.
2 worn main pivot on the derailleur (see picture) check for any sideways play.

I was brought up with the hanger being part of a quality frame and separate hangers being cheapo. With symptoms similar to these and having replaced and lubricated the cable, I asked at my friendly lbs (Sowerby Bros, Mirfield) and the immediate answer without seeing the bike was the hanger and bingo. I was amazed to learn that the hanger is now considered a sacrificial part.

[tykeboy2003]

I was brought up with the hanger being part of a quality frame and separate hangers being cheapo. With symptoms similar to these and having replaced and lubricated the cable, I asked at my friendly lbs (Sowerby Bros, Mirfield) and the immediate answer without seeing the bike was the hanger and bingo. I was amazed to learn that the hanger is now considered a sacrificial part.

My tourer has the hanger as part of the frame and has had to be "adjusted" (ie bent back into line) on numerous occasions. That was until after I managed to ruin the threads in the derailleur mounting hole, a mate cut it off and welded on a new one which he'd made from stainless steel, since then I've had no bother with it.