RD Cage length

[Super_mil]

So, I trashed my RD the other evening (the path zigged right, I could have sworn it went straight) and I don't think I can reair it (i.e. bend it straight) as its bent in all kinds of directions, so I need a new one

 

 

 

I know that the cage length controls cage (edit: chain) tension, which allows you to access more or less gears (if I'm not mistaken). So my question is where do medium cages fit into the equation and will a medium cage be able to access all the gears? I was running a SRAM X.7 (long cage) until Tuesday, so can it be replaced by the medium cage equivalent?

 

 

 

ThanksSuper_mil2009-03-19 06:26:57

[Super_mil]

Okay, found an answer that makes sense.

 

 

 

For those interested, the medium will work, just have to be a bit more selective about the gear selection especially at the extremes.

 

 

 

You can check out a logical answer here --> http://forums.mtbr.com/showthread.php?t=205890

 

 

 

Pretty sad to be answering your own posts

[Johan Bornman]

It all depends on the size of your maximum gear in the back cassette. If your largest one is a 28, you'll get away with a medium cage but if your largest sprocket is 32 or larger, you'll have to buy a long cage.

 

Cages are rated in number of teeth. If you can get the rating somewhere (it is not stamped on the RD), you'll get a number - say 30. That means the cage can handle a cumulative difference of 30 teeth. Calculate like this.

 

Largest back minus smallest back = X teeth. 34-12=20 teeth.

Plus

Largest front minus smallest front = Y teeth. 44-28=16

 

Total capacity required is 36 or better. Your (fictitious) cage can only handle 30, it is too short.