Problems: Poor shifting & Chain suck behind cassette.

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Nasty1
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Problems: Poor shifting & Chain suck behind cassette.

Postby Nasty1 » Sun Dec 23, 2012 19:53 pm

Hi

I have been suffering a few problems with poor shifting and chain suck down behind the cassette. I am running Shimano SLX 2x9 setup with XT cassette and chain.
My shifting problems are whenever I try to shift into the biggest ring on the cassette, after a very short time the chain will suck down behind the cassette and it does not matter how I set it up or the set the stop screws up to prevent over shifting. I get this no matter whether I am in the large or granny ring up front!

I am beginning to think that it is an accumulation of both chain alignment and chain tension. I have attached some photos to show both.

I would appreciate some ideas on what the cause maybe and also whether I can change the chain alignment by playing with the spacers on the BB? I have 2 on the chainwheel side and 1 on the other. Is it just a case of what I take out from one side I put back into the other?

Cheers

Adie

Image
Chain Alignment - big front to small rear

Image
Chain Alignment - big front to big rear

Image
Chain tension - big front to big rear

Image
Chain tension - big front to little rear.

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cooldad
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby cooldad » Sun Dec 23, 2012 20:42 pm

The low stop has to be wrong. If it's right it can't overshift.
And you shouldn't be using big/big ever. Or you'll be saying bye bye to that nice shiny mech very soon.
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Chunkers1980
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby Chunkers1980 » Sun Dec 23, 2012 20:46 pm

Front has nothing to do with the rear. Adjust the stop more. CD - it's a 2x you should be able to use them all

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cooldad
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby cooldad » Sun Dec 23, 2012 20:54 pm

Aaah fair enough. I have and I do.
But issue has to be adjustment
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cooldad
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby cooldad » Sun Dec 23, 2012 20:55 pm

It is nice and shiny though - I got that right.
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Nasty1
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby Nasty1 » Sun Dec 23, 2012 22:02 pm

Yes it is shiny because it is maintained! If it was full of shoot I could understand the shifting probs and you would see naff all.
The chain sucks or overshifts on the change to the big rear sprocket and ends up behind the cassette down in the spokes. I can adjust the stop screw to the point that it will not shift onto the big sprocket and then slowly back it off until it will. Within a very short space of time it will suck or overshift down behind the cassette and chew into my spokes again. Running gear should be good (300 miles old)

I take it the chain tension and alignment look OK?

Cheers

Adie

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Ouija
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby Ouija » Mon Dec 24, 2012 01:33 am

Chain is way too short. When in the big front small rear the derailleur should not look like this...

Image

That derailleur should be almost folded down with the chain going almost two thirds of the way round the sprocket. If it's that tight on the big front/small back it's no wonder it's nearly being ripped off when you move it up to the big ring on the cassette. This is usually caused by a short chain but can also be caused by tightening the tension screw that sets the rotation position of the derailleur. Look at the derailleur closely and you should see three screws. Two side by side which limit how far the derailleur can move furthest to the left and right and a third screw that sets chain tension. If that third screw is all the way in i'd highly recommend screwing it most of the way out so that the whole derailleur swivels forwards and slackens off chain tension.
Last edited by Ouija on Mon Dec 24, 2012 12:37 pm, edited 1 time in total.

Chunkers1980
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby Chunkers1980 » Mon Dec 24, 2012 08:01 am

Chain looks fine.

I'd just adjust the b tension screw to how it should be set.

I really don't think you could have set the limit correctly. It should just allow the chain to get to the big cog and certainly be no more than the middle of the cog matching the centre of the chain

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The Rookie
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby The Rookie » Mon Dec 24, 2012 08:07 am

Ouija's talking rubbish, with Chunkers thjat chain looks spot on for big big.

What you're getting isn't chain suck....

Upper wheel looks to close to the large ring, so that's the B-stop adjustment, the H stop is there precisely to stop over shifting so to me it sounds like normal adjustments needed.

Nasty1
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby Nasty1 » Mon Dec 24, 2012 08:27 am

OK, I'll play with the B-Stop and fiddle some more.

Cheers

Adie

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The Rookie
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby The Rookie » Mon Dec 24, 2012 10:38 am

Check partktools or some of the guides on youtube, but make sure you get a good one!

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Ouija
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby Ouija » Mon Dec 24, 2012 12:44 pm

The Beginner wrote:Ouija's talking rubbish


Upper wheel looks to close to the large ring, so that's the B-stop adjustment


Nice to see you didn't actually read my post then..... The B stop adjustment was my recommendation too (though i didn't call it that by name).

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The Rookie
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby The Rookie » Mon Dec 24, 2012 20:33 pm

I did, you said the chain was "way too short" which was rubbish......That mech looks spot on for big-big.

gezebo
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby gezebo » Mon Dec 24, 2012 23:00 pm

Tbh the jockey wheel looks too far away ('b' stop) imo! Although difficult to tell from the pics.

Agree that its very likely to be related to h/l adjustment if everything else is done right. I'd try starting the indexing again from bottom up. If you get this right then it would be unlikely to require the top stop in the first place.

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Ouija
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby Ouija » Mon Dec 24, 2012 23:19 pm

The Beginner wrote:I did, you said the chain was "way too short" which was rubbish


Ahh! A man who doesn't even read past the first sentence of a post...

Ouija wrote:This is usually caused by a short chain but can also be caused by tightening the tension screw that sets the rotation position of the derailleur.


Also

The Beginner wrote:That mech looks spot on for big-big.


But not for Big/Small, which is what i believe i pictured and commented on.
Last edited by Ouija on Mon Dec 24, 2012 23:27 pm, edited 1 time in total.

Chunkers1980
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby Chunkers1980 » Mon Dec 24, 2012 23:27 pm

Eh? That's all a load of rubbish.

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The Rookie
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby The Rookie » Tue Dec 25, 2012 16:34 pm

Ouija wrote:Chain is way too short.

Verdict is guilty....you were talking rubbish and and are now digging a bigger hole......

Nasty1
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby Nasty1 » Wed Dec 26, 2012 00:13 am

Oi, I appreciate the advice guys but no need to biatch about each other like a bunch of girls!

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supersonic
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby supersonic » Wed Dec 26, 2012 00:18 am

The chain length is correct, so leave that as it is.

Check the mech hanger is straight and the cassette sprocket is straight and true with no damaged teeth.

With the stops, as little as an 1/8th of a turn can make the difference.

mattv
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Re: Problems: Poor shifting & Chain suck behind cassette.

Postby mattv » Wed Dec 26, 2012 09:52 am

That chain does look slightly short. This bike is double and bash? There is no need to put that much tension on the mechanism spring. Two more pictures please, chain in little ring and smallest sprocket on the cassette. Also see if you can get one close up of the gap between the jockey wheel and cassette when in small chainring, big ring on cassette.


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