B screw backed right out - jockey gap still too much?

[Planemo]

I have been struggling with my shifting recently and it seems something is wrong somewhere because even with my B screw backed right out the distance between the jockey and the cassette is still a little too big I believe. Whether it's enough to cause the problem I have I'm not convinced but either way I'm sure it's not 'right' so I'd like to try and rule it out.

This is a long cage 12sp Shimano SLX SGS on a SRAM NX PG1230 11-50 with an XX1 chain. All the parts are in excellent order and although I haven't checked/replaced the hanger nothing has happened back-end wise and I don't even lay the bike down on that side.

The issue I am having is that I can get the upper and lower end to to shift correctly but doing so leaves hesitation when shifting around the centre of the cassette. Yesterday I went back to scratch, removed the cable and set up everything from the start, end stops bang on and still have the same problem. It's not horrendous by any means but its deffo not as crisp or selective as it should be IMO, especially when the upper and lower end of the cassette is noticeably better.

A few pics to maybe help illustrate. 1st pic shows chain on biggest cog - about 20mm gap - should be about 15? 2nd pic shows chain on 2nd cog - about 8mm gap - should be less than 5mm? And finally pic of chain on smallest cog to show length - looks about right and was shortened to the same length as the stock one when I fitted it.

Any pointers welcome!

 

[VWsurfbum]

Chain length and gap look OK to me (obviously without being there hard to tell) I would suggest if it's just hesitant to shift in the middle gears it's the chain wear and cassette pick-ups worn.

 

[Planemo]

Cheers for your thoughts. I did check the chain with another checker I have (my last one was shite) and it's not registering 0.5 wear yet. The cassette seems in really good order too - I think theres about 1700 miles on it now but the bike rarely sees water or mud tbh. And, I can get it to shift crisply in the middle but then I sacrifice shifting on either the low or high ends. so I don't think it's a cassette wear problem?

And it still seems strange that the B screw has to be all the way out...surely it shouldn't have to be?!

I did read somewhere that the SRAM/Shimano indexing at the shifter (I forgot to mention I am using an SLX shifter too) is slightly different...whether thats enough to send it out across the spread of 12 gears I don't know but I would have thought the problem I am having would be more common if it was.

 

[alancube]

Are you using aftermarket idlers, they look small?

 

[Weeksy]

If you can get some with it one way, some with it another, that screams bent hanger to me. Borrow a mech hanger alignment tool from someone to remove it from the discussion

 

[Planemo]

Both jockeys are 13t, same as the OE ones I took off.

Yeah as much as I hate to admit it I agree, hanger really needs to be checked to be able to rule it out. I'm OCD with clouting the derailleur but who knows.

 

[Mik3F]

Another one here who says to get the hanger checked, a slight bend can cause the issues you are seeing

 

[RickBullotta]

Get rid of those aftermarket pulley wheels unless they offer some lateral movement. Otherwise you'll find it quite noisy. Also, ALWAYS check derailleur hanger alignment when shifting is poor - you'd be amazed how many bikes pass the "eye test" but are way off. And lastly, it could be a small kink or bend in the derailleur inner cable.

 

[Bontee]

My transmission does something similar,Xt rear mech,slx cassette and shifter,doesn’t shift cleanly between 7 and 8 ,to be fair the transmission is original and has done over 2,700 miles now.
I put it down to wear and tear,12 speed tranny’s are pretty susceptible to mischanging in a way that even 11 speed is not.
I am probably going back to 11 speed,12 is really not needed on an ebike.
My mates 12 speed does the same on his acoustic bike and his ebike,not a lot to be fair but it’s there.

 

[Planemo]

Get rid of those aftermarket pulley wheels unless they offer some lateral movement.

Why would one want lateral movement on a part that I would have thought would want to be as slop-free as possible for accurate engagement/alignment?

ALWAYS check derailleur hanger alignment when shifting is poor - you'd be amazed how many bikes pass the "eye test" but are way off. And lastly, it could be a small kink or bend in the derailleur inner cable.

I've ordered a tool, I'm not giving up until I find the reason for this. I will update with what I find!

 

[Paulquattro]

Why would one want lateral movement on a part that I would have thought would want to be as slop-free as possible for accurate engagement/alignment?

Hi
Because it allows for slight manufacturing tolerances especially when other stuff is also worn
Putting new pulleys on an older transmission can show the wear more hence the comment for a little lateral play

 

[Weeksy]

I am probably going back to 11 speed,12 is really not needed on an ebike.
My mates 12 speed does the same on his acoustic bike and his ebike,not a lot to be fair but it’s there.

I could effortlessly go to a 10 speed on the Eeb in truth, if i had say a 46T biggest cog on the cassette that would be perfectly fine IMO. Possibly even a 42. I've ridden the wifes old Liv with a 36T biggest and only a few times did i need more.

 

[Entonox]

I recently found out there's a B-screw alignment line on the back of Shimano 12 speed mechs for 51T (excuse the filth).

 

[Mikerb]

the 2 most significant elements that impact on the B tension gap are the B tension screw..........obviously not in your case since it is wound out completely...............and chain length. Are you sure the chain is running the right way, and also is sitting correctly on the chainwheel?

 

[Planemo]

Yeah the alignment mark isnt far off but it does say '51' which of course mine isnt (its a 50) but I wouldnt think it would make much difference. Plus I'm still not sure it explains the reason for the screw being backed right out.

Chain is deffo on the chainring correctly, it wont sit on the chainring properly if its a tooth out. And the chain isnt directional? The quicklink is, and thats on correctly.

Chain length is indeed a factor in B clearance but I'll check. In my investigations I found that a longer chain would bring the jockey closer to the cassette (which is what I am looking for) but I dont think the chain could be any longer given the closeness of it to the mech (shown in my pic above)?

I've put everything on hold until I get my alignment tool so I can rule out the hanger first.

Thanks for all your help guys, I'll update with the results of the hanger check

 

[Tepi]

Bension ruuvin säädössä 11-46 on rako noin 9 mm ,se toimii.Voiko se olla 50 kasetissa mainirsema noin suuri.? Minulla ei ohjetta 50 hammastukseen,se oikeaksi ketjun pituudella ja bension ruuvilla. Uskon ketjusi väärän mittaiseksi,eli onkos se liian pitkä? Shimanohan toimii kuin Intialaisen junan vessa .

 

[Mikerb]

Chain length is indeed a factor in B clearance but I'll check. In my investigations I found that a longer chain would bring the jockey closer to the cassette (which is what I am looking for) but I dont think the chain could be any longer given the closeness of it to the mech (shown in my pic above)?

agreed..assuming the mech and hanger are correctly fitted.

 

[Planemo]

Right an update then....drum roll....I found the problem!

I bought a hanger alignment tool and so as I was backing out the mech bolt to remove it I glimpsed the mech rotate....hmm that wasn't right I thought. Turns out that the mech was binding on the hanger bolt when done up tight and of course this is very bad. On closer inspection it seems the small metal circlip on the mech which keeps a small gap between the mech and the hanger had chewed into the hanger thereby removing the gap. A fumble around my shed for a suitable washer sorted the problem but ultimately it seems the hanger is made of pasta and the only proper solution is a new one.

Anyway I checked the alignment given it was all apart and it was fine. Got everything back together and now the B screw actually does something and I can go up or down from the stock alignment markings no problem. Shifting is now back to how it should be. I guess my previous mech removal a couple of months back was one too many, chewed the hanger just a little too much and I hadn't noticed it binding up when refitting.

A simple lesson learnt there - make sure you mech is free to rotate on the bolt once clamped tight to the hanger!

Cheers for all your help guys