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Shimano M772 RD- largest cassette??

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Shimano M772 RD- largest cassette??

Old 05-25-18, 10:35 AM
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Shimano M772 RD- largest cassette??

Have the above RD on my touring bike and would like to go up to a 36t cassette from a 34t. I know what the spec's say but I wonder if anyone has gone this route?
Thanks!!
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Old 05-25-18, 11:19 AM
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Originally Posted by Tandem Tom
Have the above RD on my touring bike and would like to go up to a 36t cassette from a 34t. I know what the spec's say but I wonder if anyone has gone this route?
Thanks!!
Can't help you specifically, but generally speaking, "cheating" a bigger cog than a derailleur is rated for requires you to factor in the total capacity rating and whether your gear combinations are within that capacity. If you are, then you can often cheat the bigger cog by running the chain a link short. Total capacity rating is a function of the RD cage length, for the most part.
So it would be helpful to provide this information:
Derailleur cage length (SGS or GS. SGS is longer)
Rear cogset (low-high)
Front chainrings (low-high)
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Old 05-25-18, 11:24 AM
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Cage is long, crankset is 22 low 44 high.
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Old 05-25-18, 11:25 AM
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Cassette I am considering 12-36
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Old 05-25-18, 11:38 AM
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Originally Posted by Tandem Tom
Cage is long, crankset is 22 low 44 high.

Cassette I am considering 12-36
Thanks, that was quick.

You started at the max, and this cassette puts you a little over. The SGS cage has a total capacity of 45t, with that cassette you're at 46t. It has a max chainring difference of 22t, you're right there.

One other factor that determines max rear cog rating and that is the derailleur hanger drop. It's not clear what drop the factory ratings are based on, unfortunately. (If I were to guess I'd say 28 or 30mm for MTB derailleurs.) Maybe your hanger is longer than what they used, maybe not. If your dropouts are horizontal, you can scoot the axle as far back as possible to get a little more gap. Or you could try screwing the B-tension in more.
Shimano's ratings tend to be a bit conservative. So you could try it, but it will take some tweaking, and I wouldn't get your hopes up too much. You'd have to make extra sure you don't cross-chain big-big.
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Old 05-25-18, 11:55 AM
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I've used a M771 (about the same geometry as M772) with a 11-36t cassette on 2 bikes, for a total of ~9,000 miles and counting.
No issue with clearance to largest cog, the B-screw is within its intended range.
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Old 05-25-18, 02:56 PM
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Thanks for the replies!!
I had heard that the shimanS spec's were a bit on the conservative side . Will order the cassette and go from there!
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