Shimano RD-M580 rear derailleur, Can I use it without an extender with a 36T cog
11-11-22, 12:05 PM
#1
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Shimano RD-M580 rear derailleur, Can I use it without an extender with a 36T cog
I'm trying to maximize the gear range on my mountain bike. I have a 3x with 24, 36, 46 chainrings and an 8 speed rear cassette. I know the shimano RD-m580 derailleur (rapid rise deore lx) has a max rating of 34T but I also hear that shimano is pretty conservative with their derailleur ratings. Could I shift a 36T without putting on a hanger extender? I want to avoid an extender because this bike is ridden away from civilization a bit and I don't want to add any additional failure points to the drive train. Shifting system is currently friction thumbies but I might swap in 8 speed indexing.
Last edited by kommisar; 11-11-22 at 12:19 PM.
11-11-22, 01:04 PM
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You can probably get away with doing that. I have two Shimano road systems that call for a max cog of 32T and I run an 11-34T with no problems.
Just be sure to size the chain accordingly and check it in the stand to make sure it doesn't bind in large-large or go slack in small-small.
Just be sure to size the chain accordingly and check it in the stand to make sure it doesn't bind in large-large or go slack in small-small.
11-11-22, 01:34 PM
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I'm assuming you have the SGS version. It's worth noting that it has a capacity of 45T. So using your triple crankset and an 11-36 cassette put you past that limit as well.
Minimum chain length to make this work would be slack in some gears.
Also, the difference between your current granny gear, 24x34 and what you're trying to do, 24x36, at 90 rpm cadence is 4.76mph vs 5.04mph. I personally would not advise using the 11-36t with that drivetrain.
Minimum chain length to make this work would be slack in some gears.
Also, the difference between your current granny gear, 24x34 and what you're trying to do, 24x36, at 90 rpm cadence is 4.76mph vs 5.04mph. I personally would not advise using the 11-36t with that drivetrain.
11-11-22, 01:39 PM
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I'm assuming you have the SGS version. It's worth noting that it has a capacity of 45T. So using your triple crankset and an 11-36 cassette put you past that limit as well.
Minimum chain length to make this work would be slack in some gears.
Also, the difference between your current granny gear, 24x34 and what you're trying to do, 24x36, at 90 rpm cadence is 4.76mph vs 5.04mph. I personally would not advise using the 11-36t with that drivetrain.
Minimum chain length to make this work would be slack in some gears.
Also, the difference between your current granny gear, 24x34 and what you're trying to do, 24x36, at 90 rpm cadence is 4.76mph vs 5.04mph. I personally would not advise using the 11-36t with that drivetrain.
11-11-22, 01:45 PM
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Yes the derailleur is a long cage. The cassette is a customized 14-34 so there is no problem with the wrap (44T required with the 36T cog) and sometimes the grade is steep enough and the surface is loose enough that the sustained speed at 90 rpm isn't that important but being able to muscle the steep bits while seated is.
11-11-22, 02:48 PM
#6
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IF you have friction shifters, an upgrade to 9 speed only takes a cassette & chain.
Something to keep in mind next time you need a new chain.
Another option-
Instead of a larger BIG cog, a slightly smaller BIG ring would do the same. That might make your 14T gear a bit to low though? Of course, if you have a 13T end cog laying around.....
Something to keep in mind next time you need a new chain.
Another option-
Instead of a larger BIG cog, a slightly smaller BIG ring would do the same. That might make your 14T gear a bit to low though? Of course, if you have a 13T end cog laying around.....
Last edited by Bill Kapaun; 11-11-22 at 02:52 PM.
11-11-22, 03:14 PM
#7
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IF you have friction shifters, an upgrade to 9 speed only takes a cassette & chain.
Something to keep in mind next time you need a new chain.
Another option-
Instead of a larger BIG cog, a slightly smaller BIG ring would do the same. That might make your 14T gear a bit to low though? Of course, if you have a 13T end cog laying around.....
Something to keep in mind next time you need a new chain.
Another option-
Instead of a larger BIG cog, a slightly smaller BIG ring would do the same. That might make your 14T gear a bit to low though? Of course, if you have a 13T end cog laying around.....
I thought I was min'ed out on the granny though. Does anyone know what is the smallest granny I can use on 74 BCD?
Last edited by kommisar; 11-11-22 at 03:20 PM.
11-11-22, 04:53 PM
#8
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I need 165mm cranks, so when I bought mine, I got 22-32-44's to replace the 28-38-48's I had.
It gave me a bit lower gears using "more standard" cassettes.
They shift "good enough" with the factory FDER lowered to match. OTOH, I tend to pretty much ride in the middle ring.
11-11-22, 05:04 PM
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IF you have friction shifters, an upgrade to 9 speed only takes a cassette & chain.
Something to keep in mind next time you need a new chain.
Another option-
Instead of a larger BIG cog, a slightly smaller BIG ring would do the same. That might make your 14T gear a bit to low though? Of course, if you have a 13T end cog laying around.....
Something to keep in mind next time you need a new chain.
Another option-
Instead of a larger BIG cog, a slightly smaller BIG ring would do the same. That might make your 14T gear a bit to low though? Of course, if you have a 13T end cog laying around.....
11-11-22, 05:27 PM
#10
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Normally on a triple, the max difference between the big ring and the granny is 22T in order for the front derailleur to operate correctly. So if you are at the 22T delta limit you need to shrink the big ring in order to shrink the small ring. However, I think the 74 BCD limits the granny to 24T on my crank.
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