Low sprocket minimum spec, meaningful?thing
09-06-18, 01:05 PM
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Low sprocket minimum spec, meaningful?thing
I’m cobbling together a road touring drivetrain and decided to try a 10 speed XTR M-986 GS rear derailleur which I plan to couple to my Dura Ace 7800 shifter using a Wolf Tooth Tanpan SH-10 in-line speed converter. My understanding is that the pull ratio of my Dura Ace 7800 10 speed shifter can match up to the Dyna-Sys shifting 10 speed rear derailleur when paired with the Tanpan converter.
I’ll be using a road triple crank with Dura Ace 7803 crankset and front derailleur. The XTR rear derailleur is the “GS” cage version, not the even longer “SGS” cage. I have several triple road fast club riding bikes where I want one tooth jumps so I was going to start with a 12-25 10 speed cassette. I know this works with road “GS” triple friendly rear derailleurs. I see no reason why it should not also work well with the clutched XTR M-986 GS even though the spec says that the minimum low sprocket is a 32 tooth. Am I missing something?
I’ll be using a road triple crank with Dura Ace 7803 crankset and front derailleur. The XTR rear derailleur is the “GS” cage version, not the even longer “SGS” cage. I have several triple road fast club riding bikes where I want one tooth jumps so I was going to start with a 12-25 10 speed cassette. I know this works with road “GS” triple friendly rear derailleurs. I see no reason why it should not also work well with the clutched XTR M-986 GS even though the spec says that the minimum low sprocket is a 32 tooth. Am I missing something?
09-06-18, 01:21 PM
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You're probably close enough on the small sprocket end, 11T vs 12T.
On the large sprocket end, it will mean more space between the derailleur and the cassette, and perhaps less precise shifting.
I'm still trying to figure out the shadow thing, but I think it means the derailleur sits in front of the cassette. It provides a couple of advantages, for example some protection for the derailleur being over-stretched in the big/big combination.
In your case, it won't be shadowing in the right place, but that may not actually make any real difference.
On the large sprocket end, it will mean more space between the derailleur and the cassette, and perhaps less precise shifting.
I'm still trying to figure out the shadow thing, but I think it means the derailleur sits in front of the cassette. It provides a couple of advantages, for example some protection for the derailleur being over-stretched in the big/big combination.
In your case, it won't be shadowing in the right place, but that may not actually make any real difference.
09-06-18, 05:51 PM
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Well maybe I’ll just plan on running a 12-32 cassette since Imight be doing some self contained tours on this bike. So it sounds like the shadowing has to do with positioning of the cage in relation to the climbing cogs?
09-06-18, 06:25 PM
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Shimano Shadow was introduced with the though that a parallelogram body that doesn't stick out from the frame as far won't get whacked by trail stuff as easily. Instead you got this cable levering arm sticking way out behind the body. Oh and a guide pulley that didn't track the cog's diameters as well being coaxial with the cage pivot. Andy
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AndrewRStewart
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09-06-18, 06:47 PM
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Not exactly the same thing, but I've had ZERO issues running 12-23 & similar 9 speeds with the Altus type RDER's that expect an 11-3?T
09-06-18, 07:02 PM
#6
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This guy's got it. It's likely going to shift awful with a 25t low end. Minor misalignment will make it worse. As Andy alluded to, these don't track whatever cassette you throw in, anymore--they're designed for a small range of cassettes, and deviation will cause the shifting to suffer quite a bit.
04-26-20, 01:40 AM
#7
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Good that I found this thread, any updates on this? I'm hoping to do the same by mixing up xtr and ultegra. Did the derailleur end up shifting awfully with a 25t cassette?
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