Why go longcage?
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Shimano Tech doc says, that a medium cage can take 34T in the back. Since this is the max (9s 970XTR) I dont understand why I should go longcage. I ride a standard XTR 970 44/32/22 setup. I have always used longcage RD, but a salesguy claims, that I can just use medium. Is he right?
You need to match the total capacity as well, check the tech docs.
(capacity=(largest front-smallest front)+(largest rear-smallest rear) so for a typical 42/32/22 with 11-34 you need a capacity of (42-22)+(34-11)=43
Rule of thumb (only) single chainring - short, double - medium and triple - long.
(capacity=(largest front-smallest front)+(largest rear-smallest rear) so for a typical 42/32/22 with 11-34 you need a capacity of (42-22)+(34-11)=43
Rule of thumb (only) single chainring - short, double - medium and triple - long.
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TheRookie wrote:You need to match the total capacity as well, check the tech docs.
(capacity=(largest front-smallest front)+(largest rear-smallest rear) so for a typical 42/32/22 with 11-34 you need a capacity of (42-22)+(34-11)=43
Rule of thumb (only) single chainring - short, double - medium and triple - long.
Perfect explanation! None of the other guys I asked understood the Tech Doc correctly
I have a medium on a bike with an eccentric bottom bracket so I can optimize the chainstay effective length it has 22-32-44 front and 12-34 rear. Adjusting so that it barely makes the shift to big/big when in small/small the chain is rubbing on the chain on the top/forward roller of the rear derraileur so I never use small/small. It will not work very well at all since if you don't have an adjustable bottom bracket, you will likely have an even worse situation than I do. Getting enough chain to make the big/big will probably leave your chain rubbing in at least the small/small and small/2nd smallest and maybe up to 3rd smallest.
For certain parts stiffer is more important than lighter.
No idea how you think having an EBB effects total chain growth from small/small to big/big.....however yes if you don't mind the chain being slackish in small/small (which you shouldn't really use anyway) then on some triples a medium is fine, I would've use it with the wider spacer Touring chainsets though!
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Budget 26" HT build viewtopic.php?f=10&t=110956
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Simple, if you can't move the bottom bracket to get the chain on big/big you have to go in discrete increments of 2 inches since you can only add 2 links at a time. With eccentric bb on a non-single speed bike (Sir9 set up geared) you can cut the chain to a usable length and then rotate the BB to get it so that it will just shift onto big/big. At that point you have the minimum amount of extra chain when you are on small small. Without the eccentric BB you are liable to have up to 2 inches more chain when you are on small/small since you can't optimize the effective chainstay length on big/big.
For certain parts stiffer is more important than lighter.
A pair of links is 1" not 2" , 1/2" on wheelbase as it covers two runs of course.....
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exactly, total capacity is the key.
I use a middle cage xtr rear der. and 44-32-22 front... but i use 12-27 cassette (9speed), so middle is fine for this. 11-34 + triple; long cage is the best option.
I use a middle cage xtr rear der. and 44-32-22 front... but i use 12-27 cassette (9speed), so middle is fine for this. 11-34 + triple; long cage is the best option.