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PostPosted: Thu Apr 05, 2012 12:46 am 
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Joined: Sun Jul 31, 2011 11:24 pm
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Location: Bognor Regis
Hi , i've just purchased a M980 xtr rear mech ,

so i need to upgrade my cassette, now i'm wondering which type of cassette i need . or how i work it out.
not sure if :

11 - 32
11- 34
11- 36

?


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PostPosted: Thu Apr 05, 2012 8:06 am 
retrobike rider / Gold Trader
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Joined: Sat Jan 27, 2007 10:35 pm
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Location: The desolate flats of Cambridgeshire
All of the will work, it really depends on the ratios you want, which intern depends on how hilly your intended ride is and how tree trunk like your legs are.


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PostPosted: Thu Apr 05, 2012 9:16 am 
Old School Grand Master
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Location: Penarth
...and what you are running up front, triple/double/single?


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PostPosted: Thu Apr 05, 2012 12:15 pm 
Retro Guru

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Location: Bognor Regis
Im running a triple slx crank with a matching front mech,


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PostPosted: Thu Apr 05, 2012 2:36 pm 
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if you go for an XTR Block, its only 11-34 or 11-36 in 10 Speed, I am running the 11-34 and it works like a dream.


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PostPosted: Thu Apr 05, 2012 2:48 pm 
Old School Grand Master
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Location: Antwerp, Belgium
If it's a long-cage mech, it has a 43T capacity.

43T means that the sum of the differences between smallest and largest cogs may be 43 teeth at most.

Sorry if that sounds confusing, I'll explain with an example.


If your crankset is a 24-32-42 tooth affair, that's 18T already (42 minus 24 = 18 )
If you have a 43T capacity mech, you need to take 43 and subtract 18.
So 43 - 18 = 25

Conclusion -> The difference between smallest and largest cogs on the rear must be 25 or less. In this case an 11-36 cassette would work.

Using a 41T setup (11-34 in my example) won't hurt, but with a 45T difference, the mech won't be able to handle the extreme ratios



You'll need to figure it out for your own bike, but once you get the hang of it, it's simple.


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PostPosted: Thu Apr 05, 2012 10:49 pm 
Retro Guru

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err , i've just tryed making sense of that after a few beers , i'd better read it again in the morning :)


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