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I have an old school Devinci Coyote (2002) whose Alivio rear derailleur is having trouble shifting properly. I was wondering if I could replace it with a new Deore M592 without having to change the trigger shifters (tight on the budget).

Searching on the internet seems to hint that shimano has been sticking with the 2:1 pull ratio for a long time and this could possibly be a direct drop in without much adjustments. But I would love to hear your opinion on the derailleur and the compatibility before I pull the trigger on the purchase.

  • Have you checked hanger alignment and replaced shifter cables? These two are more common causes of poor shifting than worn derailleurs. – mattnz Apr 17 at 21:03
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First, before you commit to replacing a whole derailleur you should eliminate all the potential issues that are simpler and cheaper to fix. Many shifting issues are caused by old cables and housings. There is a good chance that if you replace those your shifting issues will clear up. Other things to check are: chain and cassette sprocket wear, derailleur idler wheel wear and derailleur hanger alignment.

A 2002 Alivio equipped bike would have the MC20 8 speed groupset (source: Shimano Wikipedia page). The Deore M592 is 9 speed.

Shimano used their 'classic' 1.7:1 rear derailleur actuation ratio up to 9 speeds on MTB groups (and 10 speed on road groups) so the M952 will index correctly with the 8 speed shifter. (Lots of info on actuation ratios here).

However, 9 speed chains are narrower than 8 speed chains (10 and 11 speed chains are narrower still - see this answer) You might have a problem with the 8 speed chain fitting in the 9 speed derailleur cage.

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Yes, it will work fine. RD-M592 is designated as a 9-speed rear derailleur. All nominally 7, 8, and 9-speed Shimano mountain RDs have the same actuation ratio.

In theory putting an 8-speed chain through the cage can cause issues, as that's the area that could be sized to want a narrower 9-speed chain, but in practice it never seems to. RD-M592 in particular practically exists to be a nice but not too expensive legacy replacement rear derailleur for 8 and 9 speed mountain bikes, and I've never seen it have issues being used in this capacity.

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