tiagra long cage v short cage

koro

Active Member
Hi,

Just noticed on my wifes Spesh Allez Ellite, she has a short cage, whilst on my Defy 2, I have a long cage.. both Tiagra 9 speed. They are both compacts, and similar in every other respect.
Out of curiosity, I was wandering why the difference...is there meant to be an advantage over one from the other?

Cheers
Koro
 

alecstilleyedye

nothing in moderation
Moderator
you'll be able to put bigger sized cassette sprockets on (e.g. 32) for really low ratios for touring or steep climbs.

she'll be unlikely to get anything bigger than a 27 to fit.
 
OP
koro

koro

Active Member
alecstilleyedye said:
you'll be able to put bigger sized cassette sprockets on (e.g. 32) for really low ratios for touring or steep climbs.

she'll be unlikely to get anything bigger than a 27 to fit.
Thanks for the reply, whilst finding out the name "cage" on Google for the difference, there seemed to be a split in opinion on what you have told me. Though the superb help that I have recieved from these forums, swing it for me with your answer...

Cheers
 

TheDoctor

I've seen things you people wouldn't believe
Moderator
Location
Stevenage
Not sure I'd agree with alecetc.
A long cage lets it wrap more chain. That's it. It doesn't alter the mech geometry one iota, so it'll only cope with a road cassette. If a long cage road mech will cope with a MTB cassette, they'd not have bothered inventing MTB mechs, would they?
 

raindog

er.....
Location
France
Normally short cage goes with double chainset, and medium and long cage with triple. Not too sure why you should have a long cage with a compact.
 
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koro

koro

Active Member
raindog said:
Normally short cage goes with double chainset, and medium and long cage with triple. Not too sure why you should have a long cage with a compact.

After reading various posts on Google, I am now of the same opinion as yourself...It to me, ( a newbie ) a longer cage allows only a longer chain, so that could only be for a tripple or a larger cassete sprocket.
 

TheDoctor

I've seen things you people wouldn't believe
Moderator
Location
Stevenage
There's no particular problem with having a long cage mech with a double, other than it weighing a little bit more. But there's no benefit either, unless you might stick a triple on at some point.
 

baznav

Active Member
Short cage is for double medium/long cage is for triple because of the difference from the big ring to the little ring on a triple the mech cage has to be longer to take up the slack.
 

RecordAceFromNew

Swinging Member
Location
West London
I think this is actually a somewhat complicated subject, and quite important, since we are all getting older and older and the hills are getting higher and higher :blush:

Physics dictates that a longer cage size has no impact on the maximum allowable size of the rear sprocket, however all else being equal it can potentially allow a larger large rear sprocket (not exceeding the maximum size) because it can take up more slack in the chain.

As such the example suggested by alecs is directionally correct. Regarding the specifics certainly 32 tooth might not always be compatible with a road mech, but anecdotal evidence suggests that it is not necessarily incompatible either.

Regarding the maximum allowable rear sprocket size, Shimano's spec is generally conservative (and I am not sure if they have a lot of incentive to stop customers buying new mechs for different gear arrangements). I happen to run a Tiagra SS with a 28 tooth cassette on my Cadenza, it is obvious that 28 tooth is still some way from the maximum allowable.

For a given frame/dropout/mech, the B screw adjustment plays a critical part in determining the maximum sprocket size allowed. This explains not only how to establish but also potentially extend the true maximum sprocket size for a frame/dropout/mech combination.

For a given frame/dropout/mech and B screw setting, because what physically limits the maximum rear sprocket size is the clash of the top pulley with the large sprocket, there are also reports that using a smaller (e.g. 10 tooth) top pulley to replace a larger (e.g. 11/12 tooth) one will also increase the maximum allowable rear sprocket size.
 

Steve Austin

The Marmalade Kid
Location
Mlehworld
Shimano mechs come in 3 varieties, SS-Short, GS-medium, SGS-long
Generally speaking , you need a SGS for a MTB/tourer with a wide range block ie 11-32 and 3 rings on the front.
You can only use a SS mech on a bike with a double upfront and a close ratio block ie 12-25ish

So if you got a medium length rear mech, it MAY work with a triple upfront and it MAY work with a wide range cassette, BUT the Shimano guidance states that it won't work properly....but it does
 

RecordAceFromNew

Swinging Member
Location
West London
Steve Austin said:
You can only use a SS mech on a bike with a double upfront and a close ratio block ie 12-25ish
Sorry Steve even the Shimano spec says the SS has a maximum rear sprocket size of 27. The reality is the maximum is nearly always larger, but how much larger is depending on frame/dropout/B screw adjustment etc. What cassette is actually workable is of course also dependent on the chainset.

IMHO the double/triple chainset distinction is strictly speaking irrelevant for rear mech compatibility consideration (despite e.g. Shimano's spec sheet appearing to indicate SS/GS go with double/triple respectively), and may just confuse the determination of what works and what doesn't.

As far as the chainset is concerned the rear mech design determines the maximum capacity for chain slack that can be taken up, hence it limits the maximum front+back tooth difference (between the largest and smallest for a triple, or large and small for a double, plus that between the largest and the smallest rear sprocket, assuming one wants to use all possible front/back combinations). Apart from said tooth difference, the rear mech is for all intent and purpose blind to whether the chainset is a double or a triple.
 
OP
koro

koro

Active Member
Hi,

After posting another post on probs with the front deraileur, which has now been sorted thanks to you guys :biggrin:, I noticed that on my Giant Defy 2 the front Tiagra has a tripple sticker on it...so then I guess that even though mine is a compact, perhaps Giant fit the long cage deraileur on all..either compact or tripple shod bikes..
 
Sorry Steve even the Shimano spec says the SS has a maximum rear sprocket size of 27. The reality is the maximum is nearly always larger, but how much larger is depending on frame/dropout/B screw adjustment etc. What cassette is actually workable is of course also dependent on the chainset.
Yip I have a 28t sprocket on my summer wheels and it runs no problem, didn't want to experiment with more though :thumbsup:
 
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