Old 04-24-18, 10:58 PM
Bike Gremlin
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Join Date: Nov 2010
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Bikes: Custom made on Scott Speedster frame, Custom made on a 1996. steel MTB frame (all but frame changed at least once in the past 20 years).

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Originally Posted by Ghrumpy View Post
Not likely. It's probably not an issue of the in-out range, it's mostly the maximum cog capacity. XT Deerhead RDs have a factory max rear cog rating of 34 teeth, which is close enough probably to fudge. But that rating is only when used with the Shimano SFR dropout, which has a hanger length of 29mm, 5mm longer than the "standard" hanger. If your hanger length is less than 29mm, it's risky. Measure that first. If it's much less than 29mm, I wouldn't even try it.

If your hanger is 29mm or more, it still also matters what chainrings you have. The Deerhead was intended for use with a triple chainring, and as such can handle a 22t chainring difference and a 40t total capacity. If your chainring set has a 16t difference, you're at max capacity anyway, so I wouldn't try it then either.

If your hanger is 29mm or longer, and you have a double chainring set that is less than a 16t difference, then you will have a little spare capacity. In that case, you could run the chain a link short, which might give you the cage swing and jockey wheel gap you need to get on the 36t. You'd have to be very careful not to cross-chain big to big, but you shouldn't ever do that anyway, right? Right?
If RD chain wrap capacity is not sufficient, wouldn't it be safer to go with the optimal chain length and just avoid small-small combo? Cutting the chain too short can cause problems in the big-big combo, like you've said. But running it at optimal length, even while exceeding the RD's chain wrap capacity, can only cause nuisance when (accidentally?) shifting to small-small combo.
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