Shimano Ultegra 8050 Di2 Mid Cage with 11-32 Cassette and 53/39 Crankset Issues

Discuss light weight issues concerning road bikes & parts.
Gavin929
Posts: 23
Joined: Sun Nov 27, 2011 4:50 am

by Gavin929

I just installed a new ultegra 8050 di2 groupset on a bike and decided to use the longer mid cage rear derailleur with an 11-32 cassette. I have always used 53/39 cranksets on the road and prefer this front gearing. I really just wanted the 32 tooth for a bailout on long rides with a lot climbing (+10,000 feet). Setup was great except the rear derailleur will not handle the 53 tooth front chainring and 32 rear cog (Noticed while setting the front derailleur adjustments and not while riding). The chain is as long as it can possibly be without "sagging" in the 11 tooth rear cog and small chainring combo.

I removed the setting in e-tube to allow use of the smallest two cogs while in the little ring. I don't normally cross chain but felt like I wanted complete control of what gear I was in. I don't want this to turn into a cross chain vs gear range vs duplicate gear thread. I just want to know if anyone else has had this problem. I wonder if this is the reason shimano "locked out" the two smallest cogs in the little ring. This would allow for a longer chain and I would clear the 32 tooth rear cog just fine. The engineer in me really wants this to work in all possible configurations even if I don't use them while riding. It's more of a since of accomplishment in setting a drivetrain up perfectly than it is about being able to use the extremes in gearing.

Things I have checked:
1. That the rear derailleur is actually mid cage (GS)
2. I added more links but the chain became "saggy"
3. That the cassette's largest cog was actually a 32 tooth
4. That my "B-tension" was properly set

Bike Specs:
Custom Moots Psychlo X Disc with 423mm chain stays and 142x12 rear spacing and english threaded bottom bracket.

Please feel free to give some advice on the matter. It just seems odd that I am totally within the derailleurs max spec for chain wrap but cannot get into the 32 tooth due to chain length issues.

by Weenie


boots2000
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Joined: Mon Oct 15, 2007 9:28 pm

by boots2000

Are you set up manual, synchro, or semi-synchro?

Gavin929
Posts: 23
Joined: Sun Nov 27, 2011 4:50 am

by Gavin929

boots2000 wrote: ↑
Sat Jan 13, 2018 4:36 am
Are you set up manual, synchro, or semi-synchro?
Manual. I’m not a fan of synchro/semi.

pdlpsher1
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Location: CO

by pdlpsher1

I also have the 8050 GS but with the 50/34 and 11-34 combo. All you need to do is adjust the B screw while in the small small combo until the chain sag is eliminated. Then try the big big combo and see if you have enough chain length. Alternative, as explained in another thread in detail, you could re-engage the 'lock out' and hence you can make your chain slightly longer. With a slightly longer chain and a properly adjusted B screw you will have better shifting performance than a slightly shorter chain with a sub-optimal B screw adjustment. On my setup, with a properly adjusted B screw, with the 'lock out' disengaged, my chain doesn't sag in the small small (34-11) combo.
Last edited by pdlpsher1 on Sat Jan 13, 2018 5:58 am, edited 2 times in total.

Gavin929
Posts: 23
Joined: Sun Nov 27, 2011 4:50 am

by Gavin929

I did some tweaking to the chain length and b-screw and finally got the 11-32 to work with the 53/39 crankset. The chain length is crucial to get this combo to work correctly. I think it has something to do with how the new style rear derailleur just "floats" around without a chain. I ended up needing one more link than shimano suggested and was able to tune out in chain sag with the b-tension screw. The pulley wheel and cog are farther apart than any shimano setup I have ever had but the shifts are still flawless.

Gavin929
Posts: 23
Joined: Sun Nov 27, 2011 4:50 am

by Gavin929

pdlpsher1 wrote: ↑
Sat Jan 13, 2018 5:58 am
I also have the 8050 GS but with the 50/34 and 11-34 combo. All you need to do is adjust the B screw while in the small small combo until the chain sag is eliminated. Then try the big big combo and see if you have enough chain length. Alternative, as explained in another thread in detail, you could re-engage the 'lock out' and hence you can make your chain slightly longer. With a slightly longer chain and a properly adjusted B screw you will have better shifting performance than a slightly shorter chain with a sub-optimal B screw adjustment. On my setup, with a properly adjusted B screw, with the 'lock out' disengaged, my chain doesn't sag in the small small (34-34) combo.
How much distance do you have between your largest 34 tooth cog and the top pulley wheel of your derailleur in the 34 rear / 34 front and 34 rear / 50 front combinations?

I have 6 to 7mm of clearance between mine.

pdlpsher1
Posts: 1909
Joined: Thu Jul 19, 2012 6:09 pm
Location: CO

by pdlpsher1

I have about a 7-8mm clearance on both combinations. See the pics. You don’t need to be overly concerned on the clearance. On the shadow RD the jockey wheel clearance is the smallest when in the lowest gear. On the higher gears the clearances are very large. But that doesn’t affect shifting performance. The B screw adjustment doesn’t impact shifting performance like on the previous RD.

Pic 1- small big
Pic 2- big big
Pic 3- big big
Pic 4- small small

ImageImageImageImage


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Gavin929
Posts: 23
Joined: Sun Nov 27, 2011 4:50 am

by Gavin929

Thanks for the pics. Makes since after thinking about the borrowed shadow design. My mtn bikes have similar clearance as this one.

pdlpsher1
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Joined: Thu Jul 19, 2012 6:09 pm
Location: CO

by pdlpsher1

You're welcome. I'm glad to know it's working for you. One thing I've noticed on the shadow derailleur is the extremely high pulley cage tension. That maybe what's contributing to the good shifting performance despite the large pulley wheel clearances on the higher gears.

FWIW I have the mechanical version of the same derailleur (GS) on my tandem. With 50/34 chainrings, I run a Shimano XT 11-40 cassette. With the B screw at the limit shifting is perfect and the long pulley cage easily handles the big-big (50-40) and small-small (34-11) combos. So the B screw has a very wide adjustment range and no special adapters like the WolfTooth RoadLink is needed. The pulley wheel clearance is obviously large in the higher gears but it doesn't seem to affect shifting performance at all.

Homer8050
Posts: 4
Joined: Wed Jan 30, 2019 4:23 pm

by Homer8050

I have a shimano R8050 gs , when I shift to 36 front 32 back in semi synchro, Or even manual, after pedaling around ten to 20seconds it shifts down to 28t even when I’m not touching the shifter. Can you help me with my problem pls. All firmware are updated. Asking if you might have experienced it already. Please help.

pdlpsher1
Posts: 1909
Joined: Thu Jul 19, 2012 6:09 pm
Location: CO

by pdlpsher1

The first thing I would verify is your derailleur hanger alignment. Don't assume your derailleur hanger is straight and perfect, even if your bike is new. The shop is supposed to check the alignment on every new bike but it seems that's a lost art these days. If you don't have the alignment tool either buy one or take your bike to a competent shop that can check it for you.

Homer8050
Posts: 4
Joined: Wed Jan 30, 2019 4:23 pm

by Homer8050

Yes we did checked. We even change new hanger. It’s still the same. The derailer just shifts down by itself.


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FIJIGabe
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by FIJIGabe

Check the limit screw on both the front and rear derailleur. You may be getting some interference in one, that causes the rear to shift to preserve system integrity.
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pdlpsher1
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Location: CO

by pdlpsher1

Yeah I would back out the low limit screw and try. But I assume you have already checked that. Just curious. What happens if you put it in 52x32? On my bike I can use the 50x34 combo and the chain never moves. Lastly, when the chain goes to the 28 do you actually see the derailleur move? If the derailleur is staionary under the 32 the chain wouldn't move the 28 by itself.

by Weenie


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Calnago
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by Calnago

pdlpsher1 wrote:I have about a 7-8mm clearance on both combinations. See the pics. You don’t need to be overly concerned on the clearance. On the shadow RD the jockey wheel clearance is the smallest when in the lowest gear. On the higher gears the clearances are very large. But that doesn’t affect shifting performance. The B screw adjustment doesn’t impact shifting performance like on the previous RD.

Pic 1- small big
Pic 2- big big
Pic 3- big big
Pic 4- small small

ImageImageImageImage


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@Pdlpsher1: I cringe when you present your setup as something even remotely close to representation of an optimal setup with the new derailleurs. We have gone over this in great detail in the thread about Direct Mount Hangers. Unfortunately, until you get a hanger that properly positions your rear derailleur there’s not much that you can do. But what is shown in your pics is far from optimal.

@Gavin929: as you’ve likely discovered by now, chainlength is critical with the new derailleurs and especially with the larger cassettes. It’s easy to think your chainlength is too long initially if the B-screw isn’t set up close to where it needs to be from the start. The b-screw dramatically affects setup, in conjunction with the proper chainlength.

The lockout of the smallest two cogs has nothing to do with the slack you experienced in the small ring and small cogs. With proper chainlength and correct b-screw adjustment you can dial it in correctly so that there is no slack and the upper pulley is very close to the cogs, as close as possible without physically squeezing the chain between the pulley and the cog it’s running on. That close as you can get proximity of the upper pulley and chain to the cogs is what you strive for to achieve optimal shifting.
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