Crunchy small sprockets

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geocycle
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Joined: 11 Jan 2007, 9:46am

Crunchy small sprockets

Postby geocycle » 24 Dec 2019, 3:26pm

I’m relatively newly returned to derailleur bikes and trying to understand their foibles. I have a spa Ti audax with 11 speed 105 gearing and a spa double chain ring. The latest issue is that under load with the chain on the smallest three sprockets I get a horrendous crunching noise. So much so I barely use these sprockets which isn’t a great hardship as I don’t do fast but I have paid for them!

The shifting up and down is ok.
The chain is relatively new and the sprockets in question have not had much use.
It occurs with both chain rings.
It’s hard to replicate on the stand, rather it needs to be under load.
I swapped out the original 105 compact chain set 50/34 for the spa super compact 46/28 and reduced the length of the chain by one link.

Thoughts include b adjustment? H adjustment? Chain length? Cable?

slowster
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Re: Crunchy small sprockets

Postby slowster » 24 Dec 2019, 3:37pm

I would check the cassette lockring. If it's not sufficiently tight then I would expect problems with the top sprockets similar to what you are experiencing.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Crunchy small sprockets

Postby Brucey » 24 Dec 2019, 4:34pm

worth checking the lockring but the other thing I'd be suspicious of is the exact state of the chain. 'Relatively new' does not exclude the possibility that it is already somewhat worn; some 11s chains can wear out completely in about 1000 miles if they see hard use and less than perfect maintenance.

So I'd check the chain for wear. If it is 0.5% or less you will probably get away with a new chain on the old sprockets. If it is worn more than 1% it almost certainly won't allow a new chain to be used on the old sprockets. If the wear is between 0.5% and 1% then it might work OK with a new chain, but then again it might not; you can try it and see.

Anyway if the chain is measurably worn, it'll run on less worn sprockets, but it might run roughly rather than smoothly. The smaller the sprocket are, the more likely rough running is.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

pwa
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Joined: 2 Oct 2011, 8:55pm

Re: Crunchy small sprockets

Postby pwa » 24 Dec 2019, 4:37pm

Chain too long, allowing the mech to fold on itself in small / small combinations? Might be possible with a very small chainring. But you would notice that on the stand, presumably. It isn't just front mech rub? Is the freehub firmly attached to the main part of the hub? I've had one of those loose before.

geocycle
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Re: Crunchy small sprockets

Postby geocycle » 24 Dec 2019, 5:35pm

Thanks for the ideas, will investigate and report back.

thecycleclinic
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Joined: 20 Apr 2012, 8:58pm

Re: Crunchy small sprockets

Postby thecycleclinic » 12 Jan 2020, 10:08pm

18t gap is too big for the chai set and will lead to chain wrap problems. This is a likely cause. You would ha e less of an issue witha 14t start cassette.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Crunchy small sprockets

Postby Brucey » 12 Jan 2020, 10:44pm

OP reports the same issue with both chainrings, so chain wrap problems -although likely as you say- seem an unlikely cause of the problems reported …?

Another thought; as well as the pulleys being specific (you can't swap top and bottom ones) the lower pulley in a modern shimano RD is often directional; specifically it has shaped teeth so that it will run smoothly even when cross-chaining small-small. Should it be removed and reinstalled the wrong way round, rough running may result, certainly when running small-small, possibly big-small as well...?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

francovendee
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Re: Crunchy small sprockets

Postby francovendee » 13 Jan 2020, 8:21am

Silly suggestion, Are the problem gears full of grit?

peetee
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Re: Crunchy small sprockets

Postby peetee » 13 Jan 2020, 8:50am

The problem on the big ring escapes me at the moment but using the smallest sprockets with the small chainring is a no-no. Apart from the chain deflection causing increased wear ( making Brucey's comment highly relevant) the chain will almost certainly be running on the plate bridging piece on the tail end of the front mech.
Current status report:
Back on two wheels in deepest Pastyland and loving every minute. Mission: to enjoy big, bad hills again.

geocycle
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Joined: 11 Jan 2007, 9:46am

Re: Crunchy small sprockets

Postby geocycle » 13 Jan 2020, 9:15am

Thanks everyone, I've now had chance to tighten the lockring and found that it has improved things. Not perfect however. I'm now working on the notion that chain is probably already a bit worn whereas the three smallest sprockets have been little used. I've just got a new chain so will give that a go.

@thecycleclinic Could you elaborate a bit -I'm not quite sure what you are referring to here?

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Sweep
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Re: Crunchy small sprockets

Postby Sweep » 13 Jan 2020, 5:44pm

Brucey wrote:the lower pulley in a modern shimano RD is often directional; specifically it has shaped teeth so that it will run smoothly even when cross-chaining small-small. Should it be removed and reinstalled the wrong way round, rough running may result, certainly when running small-small, possibly big-small as well...?

cheers

How do i know if i have such a rear mech with such a lower jockey wheel brucey? Is there some sort of marking or an arrow on such jockey wheels?
I have nothing above 9 speed if that is a factor.
Sweep

mattsccm
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Re: Crunchy small sprockets

Postby mattsccm » 13 Jan 2020, 6:24pm

I'm betting that it is chain wear. The middle sprockets are usually most worn and the chain will probably match. The smaller, higher gear sprockets get less use generally so won't match the chain.
Sadly I bet a new chain will be fine on these but less on on the middle ones. May work though.

Ray
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Location: West Yorkshire

Re: Crunchy small sprockets

Postby Ray » 13 Jan 2020, 6:58pm

Although I haven't had precisely this problem, I too found that the small sprockets were useless to me, and ran less smoothly than the bigger ones.

My bike came with an 11-32 11 speed Ultegra cassette but I soon discovered that Shimano had introduced a 14-28 (in the 105 series), which I bought. This proved smoother and better for my ageing spinner's legs. However, I did miss the 32 sprocket. I then realised that the 5 or 6 larger sprockets riveted together on a 'carrier' were the same on each of the cassettes, so I swapped them over to create a nicely-spaced 14-32.

Something you might consider sooner or later?

EDIT - sorry, the large sprockets on the two carriers were not, of course, identical, but they started at the same point (20t?), creating a smooth progression from the 14-19 (rather than 11-19 on the original). Hope this makes sense!
Ray
The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt - Bertrand Russell

Brucey
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Re: Crunchy small sprockets

Postby Brucey » 14 Jan 2020, 11:45am

Sweep wrote:
Brucey wrote:the lower pulley in a modern shimano RD is often directional; specifically it has shaped teeth so that it will run smoothly even when cross-chaining small-small. Should it be removed and reinstalled the wrong way round, rough running may result, certainly when running small-small, possibly big-small as well...?

cheers

How do i know if i have such a rear mech with such a lower jockey wheel brucey? Is there some sort of marking or an arrow on such jockey wheels?
I have nothing above 9 speed if that is a factor.


there's an arrow on the lower pulley if it is a directional one. Many 9s mechs and most 10s mechs are like this.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

bgnukem
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Re: Crunchy small sprockets

Postby bgnukem » 14 Jan 2020, 1:26pm

I'm switching to 13-up cassettes on my winter and commuting bikes in future, hopefully they will last longer, tolerate slightly-worn chains better than an 11T and also wear the chain slightly more slowly as less chain articulation is required around the larger sprockets.

But the larger sprockets will weigh a few grams more so it'll never catch on!!