Chain Wrapping Up On Itself When Changing To The Smallest Chainring: Any Ideas?

[Lovacott]

Time to hit the ignore button.

Feel free.

 

[weareHKR]

there have been a few gems of wisdom which will get me over my problem.

I've not made a contribution to the thread as I feel there is sufficient advice, however, I am interested to hear how you're getting on with the problem?

 

[Lovacott]

I've not made a contribution to the thread as I feel there is sufficient advice, however, I am interested to hear how you're getting on with the problem?

I won't know for certain until I get the new rear mech tomorrow, but it seems to be a very weak rear derailleur tension spring.

I'll post an update once I've fitted the replacement.

 

[weareHKR]

I won't know for certain until I get the new rear mech tomorrow, but it seems to be a very weak rear derailleur tension spring.
I'll post an update once I've fitted the replacement.

Cool... good luck... 🍀

 

[Ajax Bay]

fair bit of opposing force on the rear derailleur which in turn, weakens the spring.

The amount of tension in a spring (generally) below its elastic limit does not weaken the spring. The spring's strength will very very slowly reduce with age, and yours is 6 years old. The ability of the RD to provide sufficient tension in the return stretch of the chain will be undermined by a chain which is too long.

I've been sizing my new chains based on the original, because the original worked like a treat.
On the subject of chain length, can you fathom this?

"The original worked a treat." You mean you didn't experience chain suck with it. This does not mean it was the correct length.
"Can I fathom this?" Yes, but for your set up (a) I hope you are using the second example (note that the recommendation is two half links); and (b) why not just tell us that you have checked this on your current chain.

there have been a few gems of wisdom

I'd like to think that I've avoided any replies which a reasonable person could construe as contemptuous, patronising, or vitriolic. Exasperated, maybe, but hey, ho. My aim is to get you the best outcome. AS a matter of interest, which gems of wisdom do you most appreciate, from this thread?
Here's a selection below (I've left my contributions out because you have implied they have offered you no value):
Immediate response from @Gunk "Sounds like the chain could be too long, have you recently changed it?" (answer - chain is new)
@accountantpete "It's called chain suck. . . . [mine] was remedied by cleaning the chainset"
@Darius_Jedburgh: "Effective chain length is too long so you are getting chain suck." (answer: the old chain was fine, so the new one must be the right length)
@fossyant "Possibly worn chain ring also. Mud and dirt also cause it."
(and @Paulus)
@Milkfloat (and I - you have typed up lots of 'responses' but not offered these data or images)
let’s see a side on photo of the derailleur in small-small and the same angle photo but with the chain off (so no tension) on the derailleur. You could also tell us the range of teeth on the chainrings and cassette.
This looks to me to be the only 'wisdom' you feel has merit:
@SkipdiverJohn: "Maybe your rear mech spring has lost some of it's strength so can no longer provide enough tension."
Hope the new RD arrives and fits OK (direct mount onto standard hanger - you ignored the advice on that thread too).

 

[Lovacott]

@Darius_Jedburgh: "Effective chain length is too long so you are getting chain suck." (answer: the old chain was fine, so the new one must be the right length)

That may well be the case and I'm pretty sure I've never said otherwise.

The only yardstick I have is the measurement of the original chain against the new one.

I only came on here to ask a question about my bike.

I wasn't expecting a kicking!!

 

[davidphilips]

I only came on here to ask a question about my bike.

I wasn't expecting a kicking!!

Lol, Thing is its very easy to take some one up wrong when you are reading a reply, if there where a few cyclists (friends) sitting around talking any thing even name calling would be considered banter or fun. best thing is lots have tried to help, you posted a question and CC members have spent there time trying in my view to help not give any one a bad time, ps good luck.

 

[Ajax Bay]

Place the chain over the largest sprocket and the largest chain ring and bring the ends together without routing the chain through the derailleur.

Notes:
1) Their "2 links" measure one inch.
2) If 'in between', go longer, not shorter.
3) Cannot be sure the old chain was the correct length, even if you fitted it.

 

[Lovacott]

I

Lol, Thing is its very easy to take some one up wrong when you are reading a reply, if there where a few cyclists (friends) sitting around talking any thing even name calling would be considered banter or fun. best thing is lots have tried to help, you posted a question and CC members have spent there time trying in my view to help not give any one a bad time, ps good luck.

I appreciate the responses to my original question and without jumping the gun, I'm pretty confident that my problem has been solved (I'll know for certain by Sunday afternoon).

When someone asks "have you checked the length of your chain" and I reply "yep", I'm not looking for a fight.

I'm simply answering a question.

No malice aforethought.

 

[Lovacott]

Place the chain over the largest sprocket and the largest chain ring and bring the ends together without routing the chain through the derailleur.
View attachment 569227
Notes:
1) Their "2 links" measure one inch.
2) If 'in between', go longer, not shorter.
3) Cannot be sure the old chain was the correct length, even if you fitted it.

I've fitted my chain by following the instructions on the tin.

This is where Shimano go wrong in their tech docs.

They show a groupset without a rear mech in their chain sizing examples?

I amazes me how many thousands of hours are put into the design and production of anything mechanical whilst the technical documentation to support it is nothing more than a "back of a fag packet" afterthought.

 

[Ajax Bay]

They show a groupset without a rear mech in their chain sizing examples?

Deliberately so. Follow the image you've shared and your chain will be the correct length. The extra one inch link makes the allowance needed when the chain is threaded through the RD cage. When in small/small the return stretch of the chain should be 8-15mm clear of the chain going round the tension pulley.

 

[Lovacott]

Deliberately so. Follow the image you've shared and your chain will be the correct length. The extra one inch link makes the allowance needed when the chain is threaded through the RD cage. When in small/small the return stretch of the chain should be 8-15mm clear of the chain going round the tension pulley.

I don't doubt what you say for a second, but two links added to take up a whole rear mech? That's why I questioned the picture I posted.

I'll test it tomorrow when I fit the new rear mech with the old chain.

 

[Ajax Bay]

two links added to take up a whole rear mech?

Well I've just gone out and measured the difference in chain run (with chain on large/large) between 'direct' and 'through the RD cage' of my most accessible bike.
About 38mm. So that's one inch plus a bit to the next full link.
The cage 'axis' points at about 4:30 o'clock when in large/large. 4 o'clock is the closest to the horizontal acceptable. Of course I aim never to shift into large/large but at night (can't see to check cassette or chainring selection) and when tired, these things happen. The chain MUST be long enough to cope, avoiding the risk of ride ending consequences.
My chainset is 52-39-30 and cassette is 12-28 so I'm close to my (old) 105 GS RD specified capacity.
On small/small I've got about 30mm gap below the tension pulley wheel, but that would be less (maybe even nil) when I put a 28t chainring on and swap the cassette for an 12-30 for seriously hilly (long) rides.

 

[Lovacott]

Deliberately so. Follow the image you've shared and your chain will be the correct length. The extra one inch link makes the allowance needed when the chain is threaded through the RD cage. When in small/small the return stretch of the chain should be 8-15mm clear of the chain going round the tension pulley.

I have a spare new chain and I've just followed the diagram using my old chain and once set, there is not enough chain left over to thread the rear mech.

I can only assume that the rear mech needs fewer links removed than Shimano claim?

On the plus side, popping a cable tie around the chain stay about 1cm behind the line of the smallest chain ring works a bloody treat.

The female body of the cable tie is exactly the right size and length to protrude out just enough to untangle a wrapping chain.

 

[Ajax Bay]

I can only assume that the rear mech needs fewer links removed than Shimano claim?

The protocol (for establishing correct chain length) works for others, so there is something awry (and it isn't Shimano).
Share the cassette range and the chainset tooth numbers, and the chainstay length (BB centre to rear axle centre) and you/we can calculate the chain length needed. Would still like to see an image of the RD from the side with chain in small/small.

On the plus side, popping a cable tie around the chain stay about 1cm behind the line of the smallest chain ring works a bloody treat.
The female body of the cable tie is exactly the right size and length to protrude out just enough to untangle a wrapping chain.

Glad that is a candidate 'pearl of wisdom' (upthread) - but I'd just point out that it might seem to work but I suspect you don't know that it works (same with me: as well as that (with new chain and new cassette and all clean) I replaced the worn middle chainring (30,000+km) - chain suck ceased.
"A mitigation I used (and actually have left it there) is a chunky ziptie round the right chainstay up where the chainstay joins the BB shell. The idea was that a chain about to suck would knock against the ziptie and 'un-suck'."
[See the last 'chain suck' thread on here (last month?) https://www.cyclechat.net/threads/p...-when-in-the-small-gears.269738/#post-6228182 ]