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Deore XT rings - narrow chain?

Old 01-30-21, 11:00 AM
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LeicaLad 
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Deore XT rings - narrow chain?

So, I have little experience with this series of cranks. It's an early FC-M730 crankset but it has SG chainrings. The outer ring has the SG sticker, half of which is given up to "For NARROW chain only".

What means "For NARROW chain only"? Was this in the period of 5-6 speed older chains? How modern does it need to be to qualify as "narrow"? Other tips appreciated.

Thank you

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Old 01-30-21, 11:18 AM
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It probably refers to the 1/8” for SS/FG/IGH vs the 3/32” for derailer gear bikes BITD when that was the only distinction required.
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Old 01-30-21, 12:12 PM
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BITD? You're referring to the late 80s-early 90s as BITD? Really? There have long been chains of various widths. When freewheels went narrow to squeeze 6 speeds into 120mm dropouts, or 7 speeds into 126mm, there were specifically narrow chains that were required. I do not know how long that lasted, nor if what Shimano is calling "narrow" in the period of these cranks means something else. But if they were all the same for derailleur bikes, then why mark it "For NARROW chains only"?
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1959 Hilton Wrigley Connoisseur (my favorite!)
1963 Hetchins Mountain King
1971 Gitane Tour de France (original owner)
* 1971 Gitane Super Corsa (crashed)
* rebuilt as upright cruiser
1971 Gitane Super Corsa #2 (sweet replacement)
1980 Ritchey Road Touring (The Grail Bike)
1982 Tom Ritchey Everest
(replacing stolen 1981 TR Everest custom)
1982 Tom Ritchey McKinley (touring pickup truck)
1985 ALAN Record (Glued & Screwed. A gift.)
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Old 01-30-21, 12:31 PM
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3/32" is narrower than 1/8". The Shimano FC-M730-SG wants a 3/32" wide chain.

https://si.shimano.com/pdfs/si/SI-T-30A-000-00-ENG.pdf

That is an internal width which became common for bikes back in the era of that crankset, or just before. We normally talk external chain width for bike when we talk about sizing them. So don't get confused.

KMC and Shimano give the internal width of their chains. KMC sells seven speed and higher chains with 3/32 internal spacing too.

However the crank doesn't determine the specific chain you use as much as the specific rear cassette does. So if your bike is a mix and match set of components, you might need to share more info. But you probably are safe with a 7 or 8 speed chain that is also 3/32 width. (I think they all are, but maybe not)

Last edited by Iride01; 01-30-21 at 12:50 PM.
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Old 01-30-21, 12:57 PM
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Thanks.
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1963 Hetchins Mountain King
1971 Gitane Tour de France (original owner)
* 1971 Gitane Super Corsa (crashed)
* rebuilt as upright cruiser
1971 Gitane Super Corsa #2 (sweet replacement)
1980 Ritchey Road Touring (The Grail Bike)
1982 Tom Ritchey Everest
(replacing stolen 1981 TR Everest custom)
1982 Tom Ritchey McKinley (touring pickup truck)
1985 ALAN Record (Glued & Screwed. A gift.)
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Old 01-30-21, 02:26 PM
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Originally Posted by LeicaLad View Post
BITD? You're referring to the late 80s-early 90s as BITD? Really?
Well, yeah. Seemed accurate and specific enough for the purpose.
If you know of an official judgement on when BITD may be used, feel free to tell me.
Originally Posted by LeicaLad View Post
There have long been chains of various widths.
Most of that has been about EXTERNAL width. Internal width have seen less changes.
Originally Posted by LeicaLad View Post
When freewheels went narrow to squeeze 6 speeds into 120mm dropouts, or 7 speeds into 126mm, there were specifically narrow chains that were required.
Best I understand the definition, they were all considered 3/32” chains, based on internal width.
Originally Posted by LeicaLad View Post
But if they were all the same for derailleur bikes, then why mark it "For NARROW chains only"?
I never said chains were entirely the same, but I believe they fit in the same definition, based on internal width. Perhaps the ”narrow” warning was to keep people from using 1/8” chains?
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Old 02-01-21, 02:23 PM
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Originally Posted by LeicaLad View Post
BITD? You're referring to the late 80s-early 90s as BITD? Really??
Not sure what the retro scene is for the US, but for the UK, there has been a cut off of 1997 for a while now as what is considered 'retro', which would count as BITD, Admittedly, the UK was a few years behind the US for MTB's to take off, so it probably is a bit too late for someone in the US although, it does coincidence with peak/crash of the MTB boom of the late 90's so it's a good break point.
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Old 02-02-21, 01:29 PM
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Originally Posted by dabac View Post
It probably refers to the 1/8” for SS/FG/IGH vs the 3/32” for derailer gear bikes BITD when that was the only distinction required.
No. 'Narrow chain' refers to IG chains, which is now replaced by the '6,7,8 speed chain', as opposed to the old 5 speed chain. They all have 3/32" inner width, but the outer width is narrower for 6,7,8 speed than 5 speed.
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