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Author Topic: Rear Derailleur long? short? medium?  (Read 1826 times)

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Offline bikehard

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Rear Derailleur long? short? medium?
« on: September 20, 2008, 01:39:58 PM »
I know that there are different lengths however, what determines whether you use a long, short or medium length?  I would assume if would be better to have a short one which would give more ground clearance???

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Online BillT

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Re: Rear Derailleur long? short? medium?
« Reply #1 on: September 20, 2008, 02:23:29 PM »
You generally want to keep it as short as possible, but it needs to be long enough to take up the slack on the small chainring and be able to move enough for the big chainring.  What bike are you putting it on?
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Offline bikehard

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Re: Rear Derailleur long? short? medium?
« Reply #2 on: September 20, 2008, 02:47:00 PM »
nothing right now.  I'm looking at doing my own custom build.  I will probably end up buying and Intense 5.5.
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Offline Garry

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Re: Rear Derailleur long? short? medium?
« Reply #3 on: September 20, 2008, 04:30:44 PM »
You generally want to keep it as short as possible, but it needs to be long enough to take up the slack on the small chainring and be able to move enough for the big chainring.  What bike are you putting it on?


It goes a little more technical than that.  Depending on your cassette and chainring choices.  Short cages are mostly meant for road biking.  But check out this link for a full description.  http://www.beyondbikes.com/bb/tech/?section=rdr

Offline jdk

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Re: Rear Derailleur long? short? medium?
« Reply #4 on: September 20, 2008, 05:06:55 PM »
If you're going to put it on a bike with 3 chainrings up front, you probably want to go with a long. You can get away with a medium but if you do much granny ring climbing it wont be able to take up enough slack on a small front/small rear gearing situation.

Garrys link does a good job of 'splaining the situation, but if you want to do some more reading on the subject there is a very good explanation on MTBR.

http://forums.mtbr.com/showpost.php?p=2911477&postcount=2
« Last Edit: September 20, 2008, 05:10:07 PM by jdk »


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Offline bikehard

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Re: Rear Derailleur long? short? medium?
« Reply #5 on: September 20, 2008, 05:39:36 PM »
thanks for the response and links. understandable now!
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Re: Rear Derailleur long? short? medium?
« Reply #6 on: September 20, 2008, 07:33:58 PM »
For a 5.5, you'd probably need a long cage derailleur if you went with a triple chainring up front and could probably get away with a medium cage if you went with a 2 chainring/bashguard setup up front.
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Offline Garry

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Re: Rear Derailleur long? short? medium?
« Reply #7 on: September 21, 2008, 08:57:18 AM »
You can get away with a medium but if you do much granny ring climbing it wont be able to take up enough slack on a small front/small rear gearing situation.
http://forums.mtbr.com/showpost.php?p=2911477&postcount=2


Also cross chaining the drive is bad for the chain - causes premature wear.  Small ring front (inner most) and small cog in the back (outermost) torques the links of the chain. If you find yourself having to use this type of gear choice just be sure to replace your chain a little more often than normal.

 

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