Problems: Poor shifting & Chain suck behind cassette.

Nasty1

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


Chain Alignment - big front to small rear


Chain Alignment - big front to big rear


Chain tension - big front to big rear


Chain tension - big front to little rear.

cooldad

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.

Chunkers1980

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

cooldad

Aaah fair enough. I have and I do.
But issue has to be adjustment

cooldad

It is nice and shiny though - I got that right.

Nasty1

Yes it is shiny because it is maintained! If it was full of shit 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

Ouija

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



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.

Chunkers1980

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

The Rookie

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

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

Cheers

Adie

The Rookie

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

Ouija

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).

The Rookie

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

gezebo

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.

Ouija

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.

Chunkers1980

Eh? That's all a load of rubbish.

The Rookie

Ouija wrote:

Chain is way too short.

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

Nasty1

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

supersonic

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

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.

The Rookie

Sheesh, before saying that check out all the guides on chain length, big/big plus one pair of links, that looks spot on in big/big......

WindyG

This thread is becoming pure comedy, must be the Xmas drink kicking in for people :-)

Nasty1

Chain length is good (and as per photos), it was checked as per most guides and was already set at Big, Big plus 2 links. No need to argue anymore on chain length.

My LBS gave the grace of a quick 5 min check on the stops and feel they are pretty good as I have got them and suggested I look else where on the setup or pay them silly money to reset the whole lot. I am goona strip it all out give it another deep clean and reset it again as the chain still comes off.

Adie

cooldad

Find a new LBS.

supersonic

What about cable tension?

The Rookie

Surely if the high STOP is set correctly that shouldn't be relevant?

gezebo

The Beginner wrote:

Surely if the high STOP is set correctly that shouldn't be relevant?

If its set up correctly then the high stop is a back up preventing mech meeting spokes rather than an essential part of the indexing process.

The Rookie

But if the high stop is set right it should also stop the mech overshifting the chain behind the cassette.