can't fix the chain - di2
12-18-21, 09:27 AM
#1
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can't fix the chain - di2
Hello,
I have a r8050 set up with 11-28 sprocket and 52-36 chainring. When getting to 11-36, the chain is saggy (even on 10-36). When shifting to 52-28, I can barely shift: there is not enough chain.
I tried with a new longer chain to get to 52-28, but the saggy problem is worse. Not sure what am I missing here?! The b-screw at first helps with one problem, but increase the other problem later.
All parts are brand new.
Thank you for your help.
p.s. will post picture when the forum will allow me (now I can't).
I have a r8050 set up with 11-28 sprocket and 52-36 chainring. When getting to 11-36, the chain is saggy (even on 10-36). When shifting to 52-28, I can barely shift: there is not enough chain.
I tried with a new longer chain to get to 52-28, but the saggy problem is worse. Not sure what am I missing here?! The b-screw at first helps with one problem, but increase the other problem later.
All parts are brand new.
Thank you for your help.
p.s. will post picture when the forum will allow me (now I can't).
12-18-21, 09:43 AM
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What rear derailleur is being used? Picture of the setup might be of some help.
52 36 seems a bit of a range for the cassette high & low.
52 36 seems a bit of a range for the cassette high & low.
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12-18-21, 09:46 AM
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You need a long cage derailleur to go with your longer chain.
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12-18-21, 09:51 AM
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i haven't installed the rear derailleur properly, it had to go a bit on an angle when being attached to the hanger. ... I just resolved it now (after 10+ hours of headache) ..but had to use a new, longer chain.
anyway, there is something I learned today.
anyway, there is something I learned today.
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12-18-21, 09:56 AM
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You should be posting this in 'bicycle mechanics' not GD.
12-18-21, 11:00 AM
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12-18-21, 11:03 AM
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Don't get too frustrated. These chain/derailleur problems get solved easy. Big gears in the back, greater than 28 teeth, need what is called a long cage derailluer. As soon as you post a picture of the Drive side of the bicycle we are kinda in the dark. Looking forward to solving this problem...
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12-18-21, 11:06 AM
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Don't get too frustrated. These chain/derailleur problems get solved easy. Big gears in the back, greater than 28 teeth, need what is called a long cage derailluer. As soon as you post a picture of the Drive side of the bicycle we are kinda in the dark. Looking forward to solving this problem...
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12-18-21, 12:45 PM
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But 52/36 in the front is a big jump. That's why the longer chain is needed, and the longer chain means the derailleur needs more chain-wrap capacity.
12-18-21, 01:34 PM
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Chain length is a function of the largest cog on the cassette and the big ring on the crankset. The RD cage size (short medium, long) is dictated by the largest cog on the cassette in conjunction with the total system capacity (determined by finding the tooth count differential on the crankset and adding it to the tooth count differential on the largest and smallest cog on the cassette).
You aren’t wrong, there’s just a couple of other factors at hand.
12-18-21, 04:41 PM
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My older short cage Ultegra 6870 came with 50/34 and 11-28. It works fine with an 11-32, even though the top pulley is quite close to the 32 cog.
I have about 28,000 miles on the groupset now, from Sept 2014. Everything still works perfectly, with fast, smooth shifts. I replaced the seatpost battery a few years ago when I started having to charge every 10 days or so. I'm kind of surprised that the buttons or the derailleurs haven't gotten worn or sloppy.
I have about 28,000 miles on the groupset now, from Sept 2014. Everything still works perfectly, with fast, smooth shifts. I replaced the seatpost battery a few years ago when I started having to charge every 10 days or so. I'm kind of surprised that the buttons or the derailleurs haven't gotten worn or sloppy.
12-18-21, 05:21 PM
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That is the benefit of hanging onto any chain that you dont need when you have a new chain. You can push in a new pin and boom, longer chain without having to buy a new chain. I always have some on hand for this exact issue.
12-18-21, 05:54 PM
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Chain length is a function of the largest cog on the cassette and the big ring on the crankset. The RD cage size (short medium, long) is dictated by the largest cog on the cassette in conjunction with the total system capacity
Last edited by JohnDThompson; 12-18-21 at 05:59 PM.
12-18-21, 07:31 PM
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I know OP has resolved his problem but I'll throw this out for conversation. I'm using an 8000 group, 50-34, 11-34 and long cage RD. The chain is properly sized big/big and I don't think I could remove a link and still have movement in the derailleur. I've got chain sag in the small ring/ two smallest cogs, maybe three. Shimano says don't use those combos but stuff happens. 
Anyway, I was wondering if one of the RDs with a clutch would help. I figure not, since it's still the same chain wrap but maybe I'm missing something.
Anyway, I was wondering if one of the RDs with a clutch would help. I figure not, since it's still the same chain wrap but maybe I'm missing something.
12-18-21, 08:55 PM
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FYI: that crankset differential is standard for Shimnao, and in general for 11-speed (until SRAM AXS). 50/34 and 53/39 are 16-tooth differential, also. As well as Praxis 48/32. Also, the new GRX cranksets use 46/30, and wait for it, 48/31 is the “wider” range crankset.
Chain length is a function of the largest cog on the cassette and the big ring on the crankset. The RD cage size (short medium, long) is dictated by the largest cog on the cassette in conjunction with the total system capacity (determined by finding the tooth count differential on the crankset and adding it to the tooth count differential on the largest and smallest cog on the cassette).
You aren’t wrong, there’s just a couple of other factors at hand.
Chain length is a function of the largest cog on the cassette and the big ring on the crankset. The RD cage size (short medium, long) is dictated by the largest cog on the cassette in conjunction with the total system capacity (determined by finding the tooth count differential on the crankset and adding it to the tooth count differential on the largest and smallest cog on the cassette).
You aren’t wrong, there’s just a couple of other factors at hand.
12-19-21, 01:40 AM
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12-19-21, 01:42 AM
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If the chain is too tight in the large-large combination, and sagging in the small-small combination, and a B-screw adjustment doesn't fix it, more chain wrap capacity (i.e. a longer cage on the rear derailleur) is the solution. Or changing the sprockets and/or chainrings to remain within the current derailleur's wrap capacity.
12-19-21, 06:59 AM
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12-19-21, 10:47 PM
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12-20-21, 11:24 AM
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Stop posting stuff like this. ALL modern drivetrains are designed to go big/big. It might make for a tiny bit extra wear but it's fine to do for short periods of time.