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I found a similar question here but no practical answers, wondering if anyone has encountered anything like this.

I have a 105 5700 long cage rear derailleur with Roadlink extender installed and an 11-34 cassette.

When downshifting (from smallest to largest sprocket) I have no problems, but when upshifting the derailleur skips a gear twice. In other words, when in the lowest gear, I shift once and nothing happens. Shift one more time and the derailleur skips the previous gear right away. The derailleur itself moves as it should but the chain stays on the previous sprocket.

The derailleur and the hanger are straight, the cables and the housing are new. I have a 38T narrow-wide chainring in the front.

Here is a sketchy diagram that shows which sprockets are skipped:

enter image description here

I couldn’t come up with a reason for why this could be happening except that the difference in the number of teeth in the lowest gears of the cassette is simply too big for the derailleur which worked just fine with a 12-28 cassette before.

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    Given that you're on a classic road 10sp system, you could replace the derailleur with a 9-speed mountain derailleur (Deore, XT, etc) instead of using the road link and get the shift performance you want with the gear ratios you want.
    – JoeK
    Jul 11 at 16:00
  • Thanks for the answer! I didn't realize such a combination would work. Jul 12 at 10:30
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    Can confirm JoeK’s suggestion. I’m using a 11–34 Deore 10 speed cassette + 9 speed Deore SLX shadow rear derailleur with 105 5700 10 speed Brifters. Combined with 46/33 chainrings it gives me a nice gear range. It doesn’t shift very crisply (could also be due to difficult cable routing, it’s a Cyclocross bike) but I can engage all gears reliably.
    – Michael
    Jul 13 at 6:38
  • Thanks @Michael! It sure sounds like the way to go, I'll start scouting around for 9-speed derailleurs. Jul 13 at 11:55
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That is the shift where having too much b-gap can cause the exact problem you describe, and the Roadlink is there to artifically increase the b-gap. It may not be solveable, and if it is then getting the b-gap as close as possible while in the large cog is likely going to be part of it. The caveat here is that if it's close enough to grind or touch, that can also make the shift lag.

Wear to the RD pivots and pulleys will make it worse because it decreases its ability to pull the chain assertively. Likewise the chain being worn could in theory make this problem worse, but not necessarily to the extent that a new chain would fix it.

If the setup was working and now suddenly it's not, pulleys would be the easy thing to look at first. 5700 doesn't natively have very much pulley slop at all, so if you find the guide pulley has much wiggle to it then you may be able to fix it with a new set.

If you had a way of increasing the return spring force, that may help solve the problem, but 5700 isn't built to make it adjustable.

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  • Thank you for your answer! If changing the jockey wheels won’t work (they are, in fact, pretty worn, and the guide pulley is wiggly), do you think switching to 105 5800 or other more modern road derailleurs/shifters and an 11-speed cassette help? For a second I thought about going for GRX but I have rim brakes. Jul 11 at 18:49
  • One other option that came to mind is using a 10-speed Wolf Tooth Tanpan and switching to a Deore derailleur. Jul 11 at 18:59
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    It depends on your goals and if changing the whole group is something you want to do. If you could lose the Roadlink and run an RD with native support for 34, yes it will definitely work better. Another way of doing it would just be leave everything else but run a nine speed XT derailleur, such as the scarce the still made RD-M772. All that said, if your pulleys are slopped out and you're having this problem all of a sudden, new pulleys will probably fix it. Jul 11 at 21:53
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    There are many threads about this here, but first and second gen Shimano road ten shifters basically work perfectly with the higher end 9 speed mountain RDs to shift 10-speed. That is a way better solution than a Tanpan. Jul 11 at 22:07
  • Oh, alright, thank you! I didn't know they are compatible, I'll read about it and probably go for it. Jul 12 at 9:27

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