blinky

I've got the cable tension on the rear derailleur to the point where shifting from the smallest rear cog (#1) to number 6 is smooth and quiet but then falling back down seems noisy and clattery - is this normal and to be expected or is there a way to get smooth shifting up and down?

sdimattia

Sounds like you need to adjust the barrel tensioner on the rear derailleur. If the chain is lagging before it shifts, the cable needs to be tightened. If its grinding, it needs to be loosened slightly.

cyccommute 

No, it is not normal. You should be able to smoothly shift in either direction. As suggested above, it might be a tension problem. It might also be a friction problem. The inner cable may be binding in the housing. If the barrel adjuster doesn’t work, try lubricating the inner cable.

Iride01 

What about 7 through 11? If you aren't getting smooth shifting through them all, then that would be taken as an issue by me even without the other issue going the other way.

You do need to look at inner cable binding. If you start in the lowest gear ratio on the back and then shift to the highest gear ratio and there is hesitation on all or some as you slowly turn the crank, then that might point more to your cable binding somewhere in the housing or shifter.

Wonder if your chain is too long? Or maybe to short if there is a problem going up to the gears with more teeth on the rear.

rccardr 

Has the chain been changed?
Some Shimano chains must be installed with the logo facing outwards.
Putting it on in the wrong way leads to all sorts of hard to diagnose shifting problems.
Check and see if that is the case here.
If not, would check chain length as has been suggested.

blinky

left it on small ring going all the way back from 11 to 1 - at about #5 or #6, the chain was lying limp over the right chain stay - the front rings are 50/34 , rear cogs are 11-32, and the derailleur cage is a Shimano GS which is medium - read on the internet that the GS is for wider gearing ranges that will result in more chain slack when the drivetrain is crosschained small-small.

And so Iride01 , I'm thinking you have a good tip & either chain too long or cage too big , maybe both or could the tension on the derailleur be too weak ??

blinky

Thanks for the thoughts, see my response to Iride01 below - I'm thinking chain length, cage size, and/or derailleur positioning/tension

Iride01 

Shimano rear DR?

The most common recommended chain sizing by Shimano is to not thread the chain through the rear DR and put the chain in the big - big combo. Then add a link or two to get you to the next correct link to split the chain at. There are exceptions though. If it's a 3x front, then many times Shimano will say to do it a different way. Other factors and even different models of Shimano will have different sizing recommendations.

If you have Shimano, then go here and look up your model DR and if it's got a DM use that otherwise what ever other UI, SI or other doc they have for your model DR will usually tell you how they want you to size it.

https://si.shimano.com/#/

I have found similar for SRAM, but they don't seem to make it easy to find documentation. Especially models that aren't in production any more.

blinky

Thanks for the link, will check it out - I have some knowledge about the way things work on a bike but not nearly the same as those who do it every day - will probably take it to a local mechanic .

cxwrench

Could be improper adjustment. Could be friction of some kind in the housing. Could be a kinked cable. Could be a frayed cable in the shifter. If you don't know how to look at and diagnose all of these you need to take it to a shop.

blinky

I agree , thanks for responding !!

squirtdad

my favorite for chain sizing is small small. also fwiw my lbs mechanic noted this is what shimano factory reccomended

cyccommute 

Start with the easy stuff first before you go looking for more complicated solutions. This is a fairly common problem and is almost always related to too much tension on the inner cable or some friction in the cabling system. All the other issues you raise range from maybe to probably not to Big Foot in reverse order. My money would be on a slight loosening of the inner cable.

Derailer tension being too weak is getting into Loch Ness kinds of solutions. Any relatively new derailer is not going to have a weak derailer spring. And by “relatively new”, I mean something made in the past 30 years. Even Shimano’s cheapest rear derailers seldom become too weak. A Tourney might but it has other issues that will likely lead to failure before the spring wears out.

cxwrench

^True^ Derailleur springs wear out so seldomly I'd go with never.

base2 

I regularly encounter weak derailleur springs. It always stems from ages of storage in the big, bigger, & biggest cogs. Small/small is not necessarily necessary, but good sense says that being stored in the least tension configuration is the best way to preserve the spring.

Shimano prides itself on the "light action" shifting of their systems. That light action has to come from somewhere.

That being said, if your bike has not been improperly stored for 25 years: Any shifting problem that is only apparent for half the cassette is almost always related to a bent derailleur hanger &/or fraying of the cable up in the shifter. Both are easily remedied.

blinky

It's a 2 year old derailleur - when I'm on the small ring and 6th cog , smallest cog being #1 , the chain is literally lying on the right chain stay - help me understand why I wouldn't think the chain might be a bit too long ??

blinky

Do you think a chain that is a bit too long might be a possibility ??

cyccommute 

First, the age of the derailer guarantees that the spring isn’t weaken. There may be other things wrong but I’m certain that a weak derailer return spring isn’t one of them.

I’m also dubious that the chain is too long given that you are in the middle of the cassette. The chain would have to be recumbent long to be that slack in the middle of the cassette. It would have to be much longer than a chain that comes out of a box to be that slack. At the very least, a chain that slack should have wrapped itself around the cassette at some point. Unless you have changed the chain lately, this slack a chain should have destroyed the derailer long ago.

What have you done to the drivetrain recently? Did you take the derailer off? Did you crash and damage the derailer or the hanger? Have you been trying to “adjust” the derailer to fix your problem? Your initial description of your problem was a fairly common and easy fix but what you are describing now is a far different and far more involved problem. Without seeing the bike…pictures would be helpful…I would suspect that the derailer has slipped off the B screw tab on the derailer hanger and rotated forward or that the derailer hanger may be broken allowing the derailer to rotate forward or, if you did remove and replace the derailer, you missed the B screw tab.

At this point, without pictures, you’ve probably exhausted Intertubz help and it would be best to have an analog person look at it.

cxwrench

Why don't you just check it and then you'll know?

blinky

thanks , I think you hit on a good bet for the issue but you lost me with Intertubz and analog person ?? maybe I've been away from this forum too long to know the buzz words .

cyccommute 

Internet help vs a real person who can physically look at the bike.

blinky

Would loosening the B-knuckle bolt/screw have any impact on chain stretch ?

cyccommute 

Tightening it might but not to take up as much sag as you are describing. You have so much sag that I suspect the B screw isn’t even engaging the stop and may even be forward of the hanger. If you aren’t going to take the bike to a mechanic, at least post some pictures.

blinky

I brought the bike to my local mechanic and he removed 2 links from the chain and adjusted the B-screw ; the B-screw adjustment not only would provide the correct spacing of large cog and pulley/chain but would also have some impact on chain tension I would imagine .

Thanks for all the help and responses!!