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I have upgraded some components of my old MTB's drivetrain as it had a Deore crankset and Alivio rear derailleur but 7 speed cassette, shifters and chain for a long long time. Now they are all 9 speed compatible with the necessary additions. However I can't shift to the biggest cog on the cassette while other gears are all good. When I switch to 9th gear on the shifter the rear derailleur barely moves. I tried to add more tension to the cable with the barrel adjusters but even though the cable gets really really tight, derailleur doesn't move enough to derail the chain all the way to the last sprocket. I can say it doesn't even try to. Just sits on the 8th gear. What do you think is wrong here?

Note: I'm trying to adjust it on the smallest chainring.

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Crankset: Shimano Deore M610 42-32-24

Chain: YBN 9 speed

Rear Derailleur: Shimano Alivio RD-M430

Cassette: Sunrace 11-32T 9s

Shifters: Shimano Acera SL-M390

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  • Did you change the wheel/freehub, or are you still running on a freehub for a 7 speed cassette?
    – Criggie ♦
    Sep 7 at 21:50
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    Freehub was already 9 speed compatible. I'll open another thread for the chain length issue.
    – Ender
    Sep 8 at 6:32

1 Answer 1

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Have you set the low limit (L) screw correctly? Sounds like it is restricting the RD on its way to the innermost cog while tension and indexing are just fine.

Here is a good tutorial: https://www.parktool.com/en-int/blog/repair-help/rear-derailleur-adjustment

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    Low limit screw! Yes, I totally forgot that :)
    – Ender
    Sep 7 at 17:54
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    @Ender Sounds like that, if the cable really goes tight, but the mech is physically blocked to move, it's very likely just that.
    – DoNuT
    Sep 7 at 17:56
  • Yes, it worked out. Totally forgot about the existence of those screws. What about the chain length? Is it correct? I also wanted to adjust b-tension screw but it doesn't seem to have an affect on the derailleur?
    – Ender
    Sep 7 at 18:38
  • No expert on chain length but I guess, the derailleur can take up 1-2 links slack. Just try riding it and if it shifts fine without any skipping, it's probably alright. Does the derailleur move from the cog with b-screw adjustment?
    – DoNuT
    Sep 7 at 18:48
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    @Ender I'm sure there are multiple methods of adjusting the b-screw but Liv's manual for example says: "Shift into the second largest cog in the cassette. If the top pulley is very close to the largest cog or touches the largest cog, the “B” tension is too low." - so better try to adjust it that way. I watched my LBS fiddle around with this quite a bit to get shifts crisp on all cogs but the first goal is pulley not running into the cogs. Also don't get too much distance in because that will affect shifting (don't know any exact numbers but ~5-10 mm are probably a good measure).
    – DoNuT
    Sep 8 at 7:04

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