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 Post subject: rear mech cage length
PostPosted: Mon Nov 06, 2017 3:02 pm 
Dirt Disciple

Joined: Sat Nov 30, 2013 5:05 pm
Posts: 40
how do I know if I need a short medium or long cage on my derailier is there a specific rear cassette and chainset each one works correctly with


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PostPosted: Mon Nov 06, 2017 3:38 pm 
Old School Hero
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Joined: Wed Sep 27, 2017 11:27 am
Posts: 244
Location: Is tintin40
the wider the spread the longer the mech cage. small tight road cassette = short cage mech. e.g. 11-28 short cage. above this then the longer cage is needed.


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PostPosted: Mon Nov 06, 2017 3:56 pm 
Dirt Disciple

Joined: Sat Mar 25, 2017 10:40 am
Posts: 19
Which derailleur? Normally you can search to find out. If you have the wrong derailleur you can get a derailleur hanger extender which are relatively cheap if you need to use the derailleur with a wider range rear cassette or are increasing the chainrings on the crankset. Didn't there used to be something like a rule to subtract the smallest cogset teeth number from the largest to get a value i.e. 32-14t would be 18 and you would look for that or more as a stated value but I don't see that listed so much nowadays. Shimano have a minimum and maximum for both smallest and largest cog plus a teeth difference maximum for the front chainset chainrings.


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PostPosted: Mon Nov 06, 2017 4:17 pm 
Retro Guru

Joined: Mon Feb 11, 2008 9:42 am
Posts: 2852
Bonzo Banana wrote:
but I don't see that listed so much nowadays.
Rear mech capacity.
It's stated on just about every mech i've bought in the last 30 years.
Front difference plus rear difference.
You also have a maximum sprocket size. (And sometimes a minimum)
So a typical MTB mech might have 39 capacity and 46 maximum sprocket size.

Like this GS mech
http://bike.shimano.com/content/sac-bik ... 00-gs.html

It'll run an 11-40 cassette paired with a 10 tooth front difference (28/38 for instance) to give a 39 capacity.
Or you can bung it on a 1x11 set up and use an 11-46. A double would put it over the capacity.


OP, what mech is it and what are you trying to put it on.


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PostPosted: Mon Nov 06, 2017 5:35 pm 
Dirt Disciple

Joined: Sat Mar 25, 2017 10:40 am
Posts: 19
mattr wrote:
Bonzo Banana wrote:
but I don't see that listed so much nowadays.
Rear mech capacity.
It's stated on just about every mech i've bought in the last 30 years.
Front difference plus rear difference.
You also have a maximum sprocket size. (And sometimes a minimum)
So a typical MTB mech might have 39 capacity and 46 maximum sprocket size.

Like this GS mech
http://bike.shimano.com/content/sac-bik ... 00-gs.html

It'll run an 11-40 cassette paired with a 10 tooth front difference (28/38 for instance) to give a 39 capacity.
Or you can bung it on a 1x11 set up and use an 11-46. A double would put it over the capacity.


OP, what mech is it and what are you trying to put it on.


Yeah I only remembered it partially forget to add the rear cog difference to the front difference to give total capacity, couldn't see anyone listing just the rear cog difference as stated.

If anyone needs a mech hanger extender Aliexpress have their 11/11 sale on soon which means you can get one for a very reasonable £1.50 approx. Maybe there is cheaper out there but I've not seen them. Handy to have in the tool box and might mean you don't have to upgrade your derailleur to use a wider ratio cassette or chainset.

https://www.aliexpress.com/item/Road-Bi ... 46279.html


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 Post subject: Re:
PostPosted: Tue Nov 07, 2017 5:40 am 
Retro Guru

Joined: Sun Oct 26, 2014 8:34 am
Posts: 557
Thanks for the link to the extenders! Have you ever used one? Anything I should know about the installation?
Kes


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 Post subject: Re: Re:
PostPosted: Tue Nov 07, 2017 11:00 am 
Dirt Disciple

Joined: Sat Mar 25, 2017 10:40 am
Posts: 19
scottproonly wrote:
Thanks for the link to the extenders! Have you ever used one? Anything I should know about the installation?
Kes


I watched this video and thought that would be useful to have. So I'm going to order a couple on the 11th. I have a preference for a single chainring at the front with no front derailleur/shifter and a wider cassette at the rear. I prefer the simplicity, lightness and reliability of that arrangement where possible.

https://www.youtube.com/watch?v=6S9qeEPR3UU


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PostPosted: Tue Nov 07, 2017 1:06 pm 
Retro Guru

Joined: Mon Feb 11, 2008 9:42 am
Posts: 2852
Only thing regarding installation is to make sure everything is aligned and the right way round!
Especially the derailleur hanger, adding that extra length makes it's straightness more important. i.e. use a tool, don't try and eyeball it.

You *might* find you have slightly slower shifting on the smaller sprockets as well. But nothing to worry about.


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 Post subject: Re:
PostPosted: Wed Nov 08, 2017 12:36 pm 
Retro Guru

Joined: Sun Oct 26, 2014 8:34 am
Posts: 557
Nice one thanks!
Kes


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