Chain slack

birdie23

I'm having one of those nights that makes me actually want to quit cycling so far...

Okay, so I've got a new set of wheels and I put on a new 12-27 cassette. Previously I was using a 12-28, so a little smaller.

First problem is instantly I manage to have the chain drop off the big cog and scuff the hub of the new Zondas Everything looks okay with that though.

I then eventually get the gears running on the big ring, shift down to the little ring and the 34/27 just will not work. Jockey rings rubbing against the sprocket so I give up and put the 12-28 on.

Now small-big works but on small-small the derailleur isn't picking up all of the chain slack and when there's no load on the pedals the chain just drags on the chainstay.

Why is this happening?!

gethinceri

Just off the hip:
Do the new wheels require a spacer to go with the cassette?
Have you done an index of the gears from scratch with the new cassette?

birdie23

Yes to both.

I think I've sussed the issue now but still don't know how to fix it.

The derailleur doesn't seem to move back as far as it needs to in order to take all the slack in small-small. What could be causing it to stick?

Zerotails99

You need more tension on the cable maybe. If that fails then try taking out a link from the chain.

chrisgal

If your jockey wheel and sprockets are rubbing you might need to adjust the b-screw.

jgsi

birdie23 wrote:

I'm having one of those nights that makes me actually want to quit cycling so far...

Okay, so I've got a new set of wheels and I put on a new 12-27 cassette. Previously I was using a 12-28, so a little smaller.

First problem is instantly I manage to have the chain drop off the big cog and scuff the hub of the new Zondas Everything looks okay with that though.

I then eventually get the gears running on the big ring, shift down to the little ring and the 34/27 just will not work. Jockey rings rubbing against the sprocket so I give up and put the 12-28 on.

Now small-big works but on small-small the derailleur isn't picking up all of the chain slack and when there's no load on the pedals the chain just drags on the chainstay.

Why is this happening?!

Steep learning curve aint it?
Tip 1
Go Back to basics and look at a few YouTube videos on set up... read the Park Tool tuorials.
How old is your chain..? they do stretch after time and can give piss poor shifting.
Check for correct chain length re links... you dont have to be Nobel Prize winner that accurate but within a ball park is required.
As an example I swap wheels constantly with differing cassettes from a flat race close ratio11-21 to a training dinner plate of 11-28 and no issues even with a short cage mech.
Repeat, go back to basics... thats Tip 2

birdie23

chrisgal wrote:

If your jockey wheel and sprockets are rubbing you might need to adjust the b-screw.

That was only a problem on the 12-27 which is strange as it's a smaller cassette than the 12-28 :?

Zerotails99 wrote:

You need more tension on the cable maybe. If that fails then try taking out a link from the chain.

I could be wrong but I thought cable tension only affected side to side movement. My problem is the derailleur body not swinging back to take all the chain slack up.

JGSI wrote:

Steep learning curve aint it?
Tip 1
Go Back to basics and look at a few YouTube videos on set up... read the Park Tool tuorials.
How old is your chain..? they do stretch after time and can give wee-wee poor shifting.
Check for correct chain length re links... you dont have to be Nobel Prize winner that accurate but within a ball park is required.
As an example I swap wheels constantly with differing cassettes from a flat race close ratio11-21 to a training dinner plate of 11-28 and no issues even with a short cage mech.
Repeat, go back to basics... thats Tip 2

It is steep at times, yeah! The indexing is fine, I've done it loads of times now. The cables need changing (was meant to do this last night but I can't find where I put my new bar tape) but other than that everything is nearly new. Chain has about 130 miles on it, 12-28 cassette has 130 on it and the 12-27 has nothing. Chain is the same length that I've ran no problems since August 2012 - I always just take out the same number of links.

My thinking now is that I might need to take the derailleur off the bike to figure out why it's not swinging back and forth properly? It moves enough to be okay in almost every gear but when force is taken off the pedals when on small cogs you can visible see how slack the chain is over the chainstay because the derailleur hasn't traveled back enough.

jgsi

Take the rear mech off and test with your hands.
It should not that easy to push against the spring and should certainly return with some force.
Give it a good soak in diesel/paraffin if need be.

mamba80

given that the RD spring that controls fore/aft movement forces the RD forward, I think it might be worth checking this spring and as everything used to work b4 new wheels/cassette, check the freehub is spinning freely, if its not, this would stop the mech from taking up chain and hence the chain slack on chain stay.

Put your old wheels back on to rule this out.

dinyull

birdie23 wrote:

Now small-big works but on small-small the derailleur isn't picking up all of the chain slack and when there's no load on the pedals the chain just drags on the chainstay.

Why is this happening?!

I'm having the exact same problem so if you do find a solution please post it on here.

I too tried adjusting the b-screw but couldn't find a sweet spot, was either too close to the cassette/cage or too loose and dragging on the chainstay. It's like the spring in the RD doesn't pick up the slack in that gear (inner ring, small cog) - although it's fine in the other gears.

keef66

It sounds to me as if the derailleur isn't mounted properly on the hanger, so the B screw isn't stopping the whole thing moving forwards.

If you do remove the rear mech, when you reinstall it make sure to rotate it backwards so the B screw clears it's stop. When tightened it should be free to rotate clockwise (ie move further from the chainrings) but the B screw should rest on the stop on the mech hanger and prevent it from rotating the other way.

All a lot easier to do than describe.

birdie23

mamba80 wrote:

given that the RD spring that controls fore/aft movement forces the RD forward, I think it might be worth checking this spring and as everything used to work b4 new wheels/cassette, check the freehub is spinning freely, if its not, this would stop the mech from taking up chain and hence the chain slack on chain stay.

Put your old wheels back on to rule this out.

Unfortunately both of the other rear wheels I've used in the last month are broken. Main reason for buying new, got sick of Easton wheels breaking but that's another story...

JGSI wrote:

Take the rear mech off and test with your hands.
It should not that easy to push against the spring and should certainly return with some force.
Give it a good soak in diesel/paraffin if need be.

keef66 wrote:

It sounds to me as if the derailleur isn't mounted properly on the hanger, so the B screw isn't stopping the whole thing moving forwards.

If you do remove the rear mech, when you reinstall it make sure to rotate it backwards so the B screw clears it's stop. When tightened it should be free to rotate clockwise (ie move further from the chainrings) but the B screw should rest on the stop on the mech hanger and prevent it from rotating the other way.

All a lot easier to do than describe.

I'll try these two tonight after a ride. I commuted on it this morning and everything runs fine as long as I don't crosschain on the inner ring.

Is there a way to get the derailleur off without breaking the chain? Will undoing the cage work fine? Guess putting it back will be fiddly but without the wheel on I'd assume they'll be enough slack...

keef66

Yes, you can remove the derailleur without splitting the chain by removing the jockey wheels. Make a note of which is which; they are different. It will be easier if you take the tension out of the chain by dropping it off the inner chainring on to the BB shell.

Simpler though is to split the chain and rejoin it with a KMC missing link or similar.

birdie23

Yeah, I'm planning to start using missing links when I next change chain. Don't need to take it off often but it's always nice for something to be easier.

I'll report back tonight.

sigorman85

New chain with new rings and cassette? Or are you using a old chain with it??

birdie23

sigorman85 wrote:

New chain with new rings and cassette? Or are you using a old chain with it??

New chain (170 miles), new cassette(170 miles), old rings (6000+ miles). Rings shouldn't have any bearing on this though. I'm 99% the problem is the derailleur.

Okay so I've got the bike on the stand this morning. Couldn't get the derailleur off as I couldn't get enough leverage with my allen key. So took out chain and thoroughly degreased everything and reapplied. Checked B-screw was sitting right and then put it all back. Started re-indexing gears. Again, slight tweak and everything was smooth as butter through the cassette on the big ring. Drop down to the small ring and instantly small-big rubs. Adjust b-screw to stop rubbing all okay again. Shift up to small-small, chain is too slack above the chainstay and the derailleur won't move back enough to take the slack. Pictures below show chain slack and then chain taut when I've physically made the derailleur take the slack.

Only problem is when I've down this when you shift to big-small again the jockey wheel are right out the back of the cassette making the chain line almost perpendicular to the ground in that gear. Derailleur just won't swing forward.

At this point almost tempted to save myself the hassle and get a new rear derailleur.

The Mechanic

Looking at the photos, the chain is too long. You need to shorten the chain according to any of the methods available. There is one on the shimano installation sheet, Shelton brown has one and you will find a few different methods on this and other forums.

birdie23

The Mechanic wrote:

Looking at the photos, the chain is too long. You need to shorten the chain according to any of the methods available. There is one on the shimano installation sheet, Shelton brown has one and you will find a few different methods on this and other forums.

I've ran this exact chain length for nearly two years, this has never happened before. If I take two links from this length (what I did when I used one of the methods in Zinn) big-big is close to tearing the derailleur apart.

Below picture is chain running on big-big

gloomyandy

Still looks like the chain is too short. On big big that does not look like it is near max. Take a look at the pictures on the park tool site:
http://www.parktool.com/blog/repair-hel ... gth-sizing

birdie23

gloomyandy wrote:

Still looks like the chain is too short. On big big that does not look like it is near max. Take a look at the pictures on the park tool site:
http://www.parktool.com/blog/repair-hel ... gth-sizing

Can we all forget chain length for a minute.

As I've said the chain is the same length as it has ALWAYS been. This problem started this week. Nearly 2 years and 7000 miles since I started using a chain this length. Something else is now wrong.

I'm nearly 100% sure that the mounting pivot is stiff. I can't get the derailleur off. Any tips?

Here's a video showing what I mean. http://www.youtube.com/watch?v=bbNv_BEDR7A

roux_guy

That doesn't look right at all. Does it feel clicky or is it grinding at all when you move it? Possibly a broken spring? If you're feeling brave you could remove the retainer clip on the back of the mounting bolt and have a look inside it.

birdie23

Roux_guy wrote:

That doesn't look right at all. Does it feel clicky or is it grinding at all when you move it? Possibly a broken spring? If you're feeling brave you could remove the retainer clip on the back of the mounting bolt and have a look inside it.

So... I decided I feel brave.

Firstly, something definitely wasn't right but nothing clicky or grindy. However, once the derailleur was off the hanger turning the bolt still wasn't easy. It was very stiff.

Took off the clip and opened everything up. The spring looks to be showing a bit of corrosion on the inside edge. I degreased and regreased everything and I'm currently attempting to get it back together... So far, my fingers hurt a lot. :x

birdie23

FIXED!

Okay, so using the gap between in the cushions in the sofa as a vice for my multitool and the tips of my cable cutters as pliers I was able to twist the spring enough to get the retaining clip back in.

Remounted to the hanger, put the wheel on and it's smooth. Derailleur takes up all the slack.

roux_guy

Cool, glad you've got it sorted :-).

birdie23

Roux_guy wrote:

Cool, glad you've got it sorted :-).

Me too, though if it happens again I'm just buying a new one... My fingers are killing! :shock:

sigorman85

birdie23 wrote:

The Mechanic wrote:

Looking at the photos, the chain is too long. You need to shorten the chain according to any of the methods available. There is one on the shimano installation sheet, Shelton brown has one and you will find a few different methods on this and other forums.

I've ran this exact chain length for nearly two years, this has never happened before. If I take two links from this length (what I did when I used one of the methods in Zinn) big-big is close to tearing the derailleur apart.

Below picture is chain running on big-big

Why would you run big to big unless you like to change your transmission alot

birdie23

sigorman85 wrote:

birdie23 wrote:

The Mechanic wrote:

Looking at the photos, the chain is too long. You need to shorten the chain according to any of the methods available. There is one on the shimano installation sheet, Shelton brown has one and you will find a few different methods on this and other forums.

I've ran this exact chain length for nearly two years, this has never happened before. If I take two links from this length (what I did when I used one of the methods in Zinn) big-big is close to tearing the derailleur apart.

Below picture is chain running on big-big

Why would you run big to big unless you like to change your transmission alot

I don't. Big-big is just a good way of judging whether you have your chain the right length...

John.T

Classic seized top pivot. Give it a good spray with WD40 and a lot of moving it back and forth. You should then remove it and try to get some proper lube into the pivot. If you know how strip it down,clean and re-grease. If you don't then don't. It is not for the faint hearted.

John.T

sigorman85 wrote:

birdie23 wrote:

The Mechanic wrote:

Looking at the photos, the chain is too long. You need to shorten the chain according to any of the methods available. There is one on the shimano installation sheet, Shelton brown has one and you will find a few different methods on this and other forums.

I've ran this exact chain length for nearly two years, this has never happened before. If I take two links from this length (what I did when I used one of the methods in Zinn) big-big is close to tearing the derailleur apart.

Below picture is chain running on big-big

Why would you run big to big unless you like to change your transmission alot

You should always be able to use big / big safely. One day you will go there and it gets expensive if you can't.

birdie23

John.T wrote:

Classic seized top pivot. Give it a good spray with WD40 and a lot of moving it back and forth. You should then remove it and try to get some proper lube into the pivot. If you know how strip it down,clean and re-grease. If you don't then don't. It is not for the faint hearted.

I stripped it down. Taking it apart wasn't too bad but getting it all back together was a battle I don't want to take on again any time soon!

desweller

Despite your finding a resolution I'd still advise taking a couple of links out of that chain. The derailleur cage should be close to horizontal with the chain in big/big.