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Old 10-24-08, 08:16 AM   #1
Stingrey
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Long Cage vs. Short Cage

After reading some of the previous posts of the long cage vs. short cage debates I'm still a bit confused. I have a double front crank (48-38T) and a 12-27 rear cassette. It looks like I have a 25-tooth chain-wrap capacity (48-38=10, 27-12=15, 10+15=25). When I view the shimano spec sheets should I be looking at the "Total Capacity" for if I need a short or long cage derailleur? It looks like a short cage should be fine from previous posts.

I've added a link to one my previous posts if it helps:

Cannondale T1000 fixer upper
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Old 10-24-08, 08:26 AM   #2
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you are totally fine with a short cage. While the 12-27 cassette is on the wide range for road bikes, the 48-38 is only a 10 tooth difference, typical road double is 53/39 (14 tooth diff).
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Old 10-24-08, 01:08 PM   #3
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There are 2 specs to be concerned about-
1. Chain wrap capacity
2. Max cog size

You're good for both with a short cage.
IF you were to get much larger with the max cog size (>28-30 or so), you'd need to go to a long cage.
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Old 10-24-08, 01:12 PM   #4
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Umm. No.

Cage length has nothing to do with max cog size. All Shimano road RDs have a max cog size of 27T (practically good out to 30T). To shift a larger cog he'd have to go to a RD in the mountain bike line.

Edit: Typo = 27T
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Old 10-24-08, 02:39 PM   #5
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Umm. No.

Cage length has nothing to do with max cog size. All Shimano road RDs have a max cog size of 25T (practically good out to 30T). To shift a larger cog he'd have to go to a RD in the mountain bike line.
According to Shimano's site, they have a max cog size of 27. And yes, the later models have some wiggle room in there. I'm on a 28 with no problems. However I did destroy an 8 speed Ultegra RD by cross shifting a 34/28 combo.
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Old 10-24-08, 04:58 PM   #6
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Thanks for the help guys. I really do appreciate the time you've spent.

I'm looking to minimize the cost since this will be a rainy season commute bike. Is there any advantage to buying a mountain bike derailleur vs. a road bike derailleur since this is a touring bike and the original rear derailleur was a Deore XT? Also is there a disadvantage to buying a long cage? (I see a lot of long cages in my price range are on sale right now)
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Old 10-24-08, 05:07 PM   #7
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Long cages work every bit as well as short cages and they can wrap more chain. Some people claim that short cages shift just a little bit 'crisper', but what use is that if you can't get the gearing you want?
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Old 10-24-08, 05:44 PM   #8
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Originally Posted by Stingrey View Post
Thanks for the help guys. I really do appreciate the time you've spent.

I'm looking to minimize the cost since this will be a rainy season commute bike. Is there any advantage to buying a mountain bike derailleur vs. a road bike derailleur since this is a touring bike and the original rear derailleur was a Deore XT? Also is there a disadvantage to buying a long cage? (I see a lot of long cages in my price range are on sale right now)
There is almost never a reason not to run a long cage derailleur. It simply has more capacity. The only *slight* advantage you get with short cage is it may shift slightly quicker and it weighs less.

MTB derailleurs will work just fine, XT, 105+ above is decent stuff.
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Old 10-24-08, 05:52 PM   #9
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Originally Posted by Stingrey View Post
Thanks for the help guys. I really do appreciate the time you've spent.

I'm looking to minimize the cost since this will be a rainy season commute bike. Is there any advantage to buying a mountain bike derailleur vs. a road bike derailleur since this is a touring bike and the original rear derailleur was a Deore XT? Also is there a disadvantage to buying a long cage? (I see a lot of long cages in my price range are on sale right now)
Just a quick note. The Shimano specs say they recommend Rapidfire shifters for the Deore XT rear derailleur I want to replace. However when I bought the bike it came with Shimano 105 shifters that I don't want to replace. Can I match the 105s with a mountain bike derailleur for this Cannondale T1000 touring bike or is this a serious no no?

The one's I am looking at are:
ULT RD-6500 GS REAR DERAILLEUR
XT M760 REAR DERAILLEUR
XT RD-M761 REAR DERAILLEUR

Last edited by Stingrey; 10-24-08 at 06:02 PM.
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Old 10-24-08, 05:57 PM   #10
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There is almost never a reason not to run a long cage derailleur. It simply has more capacity. The only *slight* advantage you get with short cage is it may shift slightly quicker and it weighs less.

MTB derailleurs will work just fine, XT, 105+ above is decent stuff.
Sweet! I've been riding for a couple years, but I'm not in dire need for anything too lightweight or quick shifting just yet.
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Old 10-24-08, 07:32 PM   #11
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I bought up a couple Ultegra GS at $39.95/Shp. Use them on my circa-1982 road machine and my Trek FX. Excellent derailleur - I usually hate Shimano. Want one?

http://www.cambriabike.com/shopexd.a...EAR+DERAILLEUR

No, I don't own stock in the company - either of 'em.
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Old 10-24-08, 08:37 PM   #12
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Quote:
Originally Posted by Stingrey View Post
Just a quick note. The Shimano specs say they recommend Rapidfire shifters for the Deore XT rear derailleur I want to replace. However when I bought the bike it came with Shimano 105 shifters that I don't want to replace. Can I match the 105s with a mountain bike derailleur for this Cannondale T1000 touring bike or is this a serious no no?
Not to worry. Shimano road brifters will shift a Shimano mountain bike rear derailleur just fine. As a matter of fact, that's a common spec for many tandems.
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Old 10-27-08, 06:54 PM   #13
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Originally Posted by urbanknight View Post
According to Shimano's site, they have a max cog size of 27.
Yes. It was a typo.
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