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Difference between Long and short Cage for Rear Derailleur


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Posted

But is does work. Working just fine at the moment.

 

Lots of things that aren't technically (and I don't meant a colloquial technically) correct work. Doesn't mean they should be used.

 

In your case, a long cage will work. Hell, a long cage will work on a road bike running 39/53 and 11/21.

 

But you asked, and the correct answer is you are using the "wrong" dérailleur.

Posted

Ok,

 

so lets modify the math a bit.

 

So my numbers: (42-24) + (34-11) = 18+23=41

 

Still trying to figure out which Derailleur front and back will work,

I'm keen on

 

FD

http://www.chainreactioncycles.com/Models.aspx?ModelID=83625

 

RD

http://www.chainreactioncycles.com/Models.aspx?ModelID=83162

 

G

 

Hi Johan

 

Now remember you mentioning this during the course.

 

So my numbers: (42-24) + (36-11) = 18+25=43

 

Rear Derailleur

I see on CRC they mention something about "Total Capacity teeth" listed as 14, I'm guessing this is a teeth capacity for the rear cassette, guess they're showing the medium cage length, being 14 teeth, can't seem to select a long cage to see the capacity there

http://www.chainreactioncycles.com/Models.aspx?ModelID=83162

 

Front Derailleur

Teeth Capacity = 18 teeth, now I think If I understand things correctly then I have a problem, I need 25.

http://www.chainreactioncycles.com/Models.aspx?ModelID=83625

 

How am I doing.

 

G

Posted

Thanks. Was the derailleur I used for my 3x9 setup. Might as well keep using it.

 

Yip. I'm a fan of conservation of resources.

Posted

You guess correctly.

 

You only need a long cage for a triple clanger up front.

 

 

its not dependant on the number of chainrings but the gearing range.

 

2x10 can use a long cage too if a 28x36 is in use.

Posted (edited)

its not dependant on the number of chainrings but the gearing range.

 

2x10 can use a long cage too if a 28x36 is in use.

 

Yes. The triple chainring just offers the simplest example of the extreme ratios to which the long cage dérailleur is suited.

 

Like I already said, the other guy's 1x9 setup will work fine with a long cage, as with you example.

 

Take it or leave it.

 

As example, show me the teeeny tiny inside chainring from a triple that will work on a regular two x's setup that makes your example work.

Edited by TNT1
Posted

I'll take it gladly,

 

Just want to understand the math around it also, and the information listed on CRC ad the Shimano sites.

 

This build is about building the bike, but learning also as i go.

 

G

 

 

 

Yes. The triple chainring just offers the simplest example of the extreme ratios to which the long cage dérailleur is suited.

 

Like I already said, the other guy's 1x9 setup will work fine with a long cage, as with you example.

 

Take it or leave it.

Posted

I'll take it gladly,

 

Just want to understand the math around it also, and the information listed on CRC ad the Shimano sites.

 

This build is about building the bike, but learning also as i go.

 

G

 

The math you'll have to ask JB and others more learned than I. I only have experience.

Posted

Ok Math guys

 

Please help explain

 

 

Rear dérailleur:

 

http://cycle.shimano-eu.com/publish/content/global_cycle/en/nl/index/components/mountain/deore_xt/product.-code-RD-M780-GS.-type-..html

 

Maximum Sprocket 36T

Minimum Sprocket 11T

Front Difference 18T

Total Capacity 35T

 

Maximum sprocket, easy enough max teeth for big sprocket. I'm good.

Min sprocket, 11, I'm good. That gives me a dif of 25

Now the Front Difference value they state, 18 teeth, so this matches the below. Now the 35T they list, how did they get to this?

 

 

Front dérailleur

http://cycle.shimano-eu.com/publish/content/global_cycle/en/nl/index/components/mountain/deore_xt/product.-code-FD-M781-D.-type-.fd_mountain.html

 

Cassette Compatibility 10

Maximum Capacity 18T

Top-middle Minimum Capacity 10T

Top Gear Teeth 42T

 

Guessing the Cassette Compatibility is related to a 10 speed rear.

Maximum capacity is 42-24 = 18

Top-middle, gues this is the teeth dif between big wheel, middle wheel, so I have 42 - 32 = 10, so good here.

Top Gear Teeth, max teeth count for big wheel.

 

G

Posted

Yes. The triple chainring just offers the simplest example of the extreme ratios to which the long cage dérailleur is suited.

 

Like I already said, the other guy's 1x9 setup will work fine with a long cage, as with you example.

 

Take it or leave it.

 

As example, show me the teeeny tiny inside chainring from a triple that will work on a regular two x's setup that makes your example work.

 

 

My my Ignacious,......... you are an aggressive little boy aren't you.

 

The longer cage derailleur with e.g. a 44,32,22 front and a 11-34 rear offers a more useful range across the cassette and front chainrings.

You can use the 44x34 or 44x30 without exceeding the capacity of the derailleur. In short it gives an extra ratio. This may be important to some people.

The same range can be achieved with other set-ups eg 2x10 or 1x11 but you may not get as many gear ratio's in the same range.

 

Take a 3 ring 44/32/22 front and 11-32 rear and mix with a medium cage and a long cage and the long cage gives you one extra ratio.

 

That's all.

I don;t consider it to be a problem because the extra ratio comes at extreme chain angles that does nto do wonders for sprocket wear or chain life.

 

I've always run a medium cage on my MTB, have for 15years.

However with 11-36 ratio cassette and 40/26 front I probably will use a log cage. I currently run 2x9 44/29 and 11/32 so there's no need for long cage.

 

wanna play with gear ratio's http://www.bikecalc.com/gear_ratios

Posted

Yo GoLefy.

 

Judging by your user name and the manner in which you compose your posts I am questioning you are the same person from the other ct based mtb email list/group.

 

If so boys and girls, them please take his advice seriously.

Posted

Yo GoLefy.

 

Judging by your user name and the manner in which you compose your posts I am questioning you are the same person from the other ct based mtb email list/group.

 

If so boys and girls, them please take his advice seriously.

His advice might be OK but his opinions need work.

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