How exact are chain capacity #'s?
07-05-20, 12:55 PM
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How exact are chain capacity #'s?
I'm going to upgrade to a 2x11 setup, 11-40 cassette and 38/28 chain rings. I calculate I need a rear derailleur capacity of 39T. If I get the medium cage Deore XT derailleur it lists its capacity as 39T. Is that cutting it too close? or will it work just fine?
07-05-20, 01:08 PM
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Most will allow a little over capacity, but then you're on your own!
Example, my 6700 rear is within the capacity # but over the max rear cog size by a couple teeth.
Barry
07-05-20, 01:58 PM
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You also need to consider the max rear cog limit of the derailleur.
07-05-20, 02:03 PM
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You may or may not get away with it. Depends too much on other things the manufacturer of those DR's can't control. So you just have to try and see. Or don't.
As previously stated, there are other specs to consider besides chain capacity.
As previously stated, there are other specs to consider besides chain capacity.
07-05-20, 02:40 PM
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Thanks, I'm OK on the max cog size, Shimano lists it as 42T (for a 2x11 setup) and I'm only going 40T. One thing that's odd in the specs is they say 42T is the largest cog size for a 2x11 setup yet the XT cranksets are either 26/36 or 28/38. Either of those configurations would need a capacity of 41 with the 11-42 cassette so those 2 specs don't agree. I'm making an assumption here that Shimano would engineer the RD to work with it's own groupseet.
07-05-20, 02:42 PM
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OK I'm sorry, I made an assumption. You asked about derailleur capacity and I answered about the same.
These other replies have gone the extra mile to determine if you have taken into account the Cog size you are using.
If you'd like to read up on the way Shimano spec's derailleurs give this a read.
I went through the same problem recently.
All the best
Barry
These other replies have gone the extra mile to determine if you have taken into account the Cog size you are using.
If you'd like to read up on the way Shimano spec's derailleurs give this a read.
I went through the same problem recently.
All the best
Barry
07-05-20, 03:19 PM
#7
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Thread Starter
OK I'm sorry, I made an assumption. You asked about derailleur capacity and I answered about the same.
These other replies have gone the extra mile to determine if you have taken into account the Cog size you are using.
If you'd like to read up on the way Shimano spec's derailleurs give this a read.
I went through the same problem recently.
All the best
Barry
These other replies have gone the extra mile to determine if you have taken into account the Cog size you are using.
If you'd like to read up on the way Shimano spec's derailleurs give this a read.
I went through the same problem recently.
All the best
Barry
07-05-20, 04:35 PM
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Exceeding the rear derailleur's wrap capacity by a few teeth should cause no problems. Assuming you size the chain long enough to allow shifting into big-big ( a necessity for safety) you may have to forgo using small-small. That is not a sacrifice.
07-05-20, 06:50 PM
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Aren't you only getting 503% range with very big steps?
You'd get closer stepping for example like 11-34 36/22. And then you have a couple of options for mixing your own cogs. I have 10 speed 12,13,14,15,17,19,21,24,28,34. For 11 speed you could take a similar set plus the 11t. Miche 11 speed cassettes can be assembled with custom cogs from a dealer from 11 to 34.
You can find 20t chainring for symmetric 4 bolt 64bcd on eBay.
Oh but I don't know if the cassette width is different between road and MTB 11 speed.
You'd get closer stepping for example like 11-34 36/22. And then you have a couple of options for mixing your own cogs. I have 10 speed 12,13,14,15,17,19,21,24,28,34. For 11 speed you could take a similar set plus the 11t. Miche 11 speed cassettes can be assembled with custom cogs from a dealer from 11 to 34.
You can find 20t chainring for symmetric 4 bolt 64bcd on eBay.
Oh but I don't know if the cassette width is different between road and MTB 11 speed.
Last edited by tomtomtom123; 07-05-20 at 06:58 PM.
