B Screw problem (bu...
 

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B Screw problem (but the opposite of normal!)

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I've been trying to set up 11 speed gearing on my hardtail (Deore M5100 mech and shifter, Microshift Shimano compatible 11-46 cassette), and it's proving to be a real bugger!

I had a similar setup working on my old frame fine, but for some reason this won't shift properly.

The problem seems to be the B screw, but not that it's too short (searching online that seems to be the most common complaint) but that it's too long even in the lowest setting, and it's pushing the mech too far from the cassette.

The Deore mech has a little part on the hanger bolt that rotates and the screw sits against that, and then that part contacts the stop on the hanger.

Is it possible to rotate that out of the way, or even remove it, so that the b screw sits directly on the stop, thus effectively shortening it?

Weird problem, and even with a fair amount of searching I can't find anyone else who has had a similar issue!


 
Posted : 12/09/2023 11:36 am
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What is wrong with the shifting?

I once had issues and tried moving that b screw "stop" piece. The b screw then only half contacted my mech hanger and ate through it on a rocky descent. Small steel screw against a relatively soft aluminium mech hanger didn't last long. The piece is there for a reason.


 
Posted : 12/09/2023 11:40 am
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<p style="text-align: left;">
What is wrong with the shifting?</p>

When adjusting it will either shift up or down, but not both without readjusting the cable tension.

On the top cassette cog the mech is miles away from it, even on lowest b screw setting.

I have never (in 30+ years of bike maintenance) not been able to get gears working properly!


 
Posted : 12/09/2023 11:45 am
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When adjusting it will either shift up or down, but not both without readjusting the cable tension.

Sounds like classic bent hanger syndrome...

On the top cassette cog the mech is miles away from it,

Are you adjusting it against the position of the cage (p21) rather than just by distance?


 
Posted : 12/09/2023 11:52 am
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I had this when putting a 12 speed XT mech onto my chameleon frame. In my case I managed to “fix” it by moving the adjustable drop outs which causes the mech mounting hole to rotate. Suspect I could have gotten a similar result if I filed a bit of the hanger off where the adjuster screw contacts.


 
Posted : 12/09/2023 12:25 pm
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When adjusting it will either shift up or down, but not both without readjusting the cable tension.
Sounds like classic bent hanger syndrome…

Or a sticky/dirty cable gives those symptoms too.


 
Posted : 12/09/2023 12:34 pm
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On the top cassette cog the mech is miles away from it, even on lowest b screw setting.

PIc ? That sounds like something is completely wrong potentially.


 
Posted : 12/09/2023 12:36 pm
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I was having a lot of issues with a new 11 speed Shimano mech and it turned out my chain was just a tiny bit too short. I hadn't realised chain lengths need to be longer with modern mechs compared to how they used to be.


 
Posted : 12/09/2023 12:57 pm
weeksy reacted
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Or a sticky/dirty cable gives those symptoms too.

I thought that - so I fitted a brand new outer and cable 🤔

Sounds like classic bent hanger syndrome

First thing I checked with my hanger alignment tool.

It all worked perfectly with previous set up, which was Microshift 11spd mech, Shimano shifter and Microshift Cassette.

Only change is a brand new Deore mech!

I was having a lot of issues with a new 11 speed Shimano mech and it turned out my chain was just a tiny bit too short

Only thing I haven't changed, though chain worked fine in previous set up.

This chain is only 5/6 rides old, but I'd have a new spare chain. Might try it with a few extra links.


 
Posted : 12/09/2023 1:02 pm
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I think it's going to be the spinny tab/locator thing in the wrong position.


 
Posted : 12/09/2023 1:03 pm
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<p style="text-align: left;">I think it’s going to be the spinny tab/locator thing in the wrong position</p>

It's currently (definitely, I've double checked!) In the right position - between B screw and hanger stop.


 
Posted : 12/09/2023 1:05 pm
dc1988 reacted
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chain needs to be much longer on new mechs than old mechs. i had exactly the same symptoms. i put 2 extra links in and its much better. i could probably put another link back in to be honest.


 
Posted : 12/09/2023 1:34 pm
dc1988 reacted
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I had to exactly the same issue with the same components. Was fine with the xt mech till I busted it. The new deore mech was so far away from the cassette it was ridiculous, nowhere near enough chain wrap on the cassette.
I took the Dremel to the rotating bit till it looked acceptable. It's this that rests on the stop on the hanger, B screw essentially isn't used.
Have an slx mech on it now and that's fine. Seems to be the swing link making it fit better.
Be interesting if the new linkglide mech ive just ordered fits without the Dremel as that doesn't use the swing link either.


 
Posted : 12/09/2023 2:52 pm
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Edit. Maybe it's due to the low sprocket min/max size being 51 on that mech and is therefore a poor fit with the 46? That's a possibility.


 
Posted : 12/09/2023 3:24 pm
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I’ve had exactly the same with a deore mech, too far away from the smaller sprockets.
Chain length made no odds.

I did fit the B link from the XT mech and that solved it but the cable outer was then at a crappy angle.

I messed about with it a fair amount and in the end I repaired my old XT mech and slung the cheapo deore mech in the spares bin.

Bloody heavy, clunky thing anyway.


 
Posted : 12/09/2023 4:20 pm
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So....tried fitting a new chain with an extra 4 links. Now shifts fine 😎

Might be ok with another couple of links removed, but I didn't want to push my luck.

So it turns out that Shimano rear mechs need a bit more chain than Microshift ones 🤷‍♂️


 
Posted : 12/09/2023 6:27 pm
dc1988 and weeksy reacted
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Good outcome. I was just cooking up a response along the lines of 'stop being so ****ing cheap' 😉


 
Posted : 12/09/2023 6:40 pm
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Good outcome. I was just cooking up a response along the lines of ‘stop being so **** cheap

😆 still prefer singlespeed, so no point in overspending on gears!


 
Posted : 12/09/2023 6:45 pm

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