tiagra gear range

davecooper
davecooper Posts: 290
edited January 2008 in Workshop
What is the largest rear cog that can be used with the Tiagra 9 speed long cage triple rear mech? I can't seem to find this info on any of the normal sites. Could a Deore 11 - 32 cassette be used with this mech?

Comments

  • redddraggon
    redddraggon Posts: 10,862
    As long as you use sensible gear selection ie not using smallest sprocket and smallest chainring, you should be fine.

    See Sheldon Brown on dérailleur capacity:

    http://sheldonbrown.com/gloss_ca-g.html#capacity
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  • tatanab
    tatanab Posts: 1,283
    The answer is on the Shimano website. It shows a maximum of 27T. That doesn't mean you cannot "make it work" with bigger sprockets so I'd say playabout with it if you feel sufficiently competent mechanically.
    http://cycle.shimano-eu.com/catalog/cyc ... 9629175657
  • redddraggon
    redddraggon Posts: 10,862
    tatanab wrote:
    The answer is on the Shimano website. It shows a maximum of 27T. That doesn't mean you cannot "make it work" with bigger sprockets so I'd say playabout with it if you feel sufficiently competent mechanically.
    http://cycle.shimano-eu.com/catalog/cyc ... 9629175657
    #

    They only say a maximum of 27T because they don't make a road cassette any bigger.
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  • John.T
    John.T Posts: 3,698
    The top jockey runs higher on 'road' mechs. You can push it a bit by adjusting the 'B' screw but the largest I have used is 28. I don't think you would get away with a 32. You will be better off using a Deore mech or any MTB one..
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  • davecooper
    davecooper Posts: 290
    Thanks guys. I did not necessarily want to go as large as 32. I currently have 8 speed STI levers but a 9 speed rear mech. I got a new pair of wheels at Christmas and thought that rather than swap the 8 speed cassette (12 -25) from my old wheels, I would take this opportunity to begin upgrading to 9 speed, replacing the STI levers at a later date. I would adjust the rear mech temporarily to use just eight of the cogs. In reality, I only wanted something slightly bigger than 25 so 27/28 would be ideal. I had been offered the 11 - 32 by a friend who had bought it by mistake, I think it will be headed for ebay now.
  • mercurykev
    mercurykev Posts: 264
    I'm currently running a tiagra long cage with a 28 - 12 cassette and it works perfectly.
  • John.T
    John.T Posts: 3,698
    Your 8sp STIs will not work 9sp very well. The 9sp cassette is the same width as the 8sp so the cog spacing is wider. You will be better off using the 8sp cassette for now and fitting 9sp STIs, cassette and chain at the same time. If you are using a triple then a 27 cog should be big enough. Staying with a standard cassette does give better changing. You will not need to change the mechs, they will work fine.
    My Fleet.
  • davecooper
    davecooper Posts: 290
    Ah yes, the cassette spacing! I was thinking that the spacing did not change until 10 speed but if it is the same width as an 8 speed, the spacing must alter. I will stick with the 8 speed for the time being.
  • aracer
    aracer Posts: 1,649
    You can make 8-speed STIs work with (8 cogs of) a 9-speed casssette, using the Hubbub cable routing mod as described in http://ctc.org.uk/DesktopDefault.aspx?TabID=3946 - this would make your upgrade programme feasible (though not with the 11-32).

    As others have said, it's very unlikely the 32 will work - tried this on my cross bike and the long-cage road mech rubbed, so I had to swap to an MTB mech. 28 will almost certainly work, and depending on your setup it's possible 30 might. Just get a 9-speed 12-27 though given your requirements.
  • davecooper
    davecooper Posts: 290
    This may be a stupid question but how does my Tiagra 9 speed mech work with the 8 speed cassette and shifters? This is as originally supplied on my Specialized Allez. This would suggest that the amount of rear mech movement for each gear change is a function of the STI lever and not the mech.
  • redddraggon
    redddraggon Posts: 10,862
    davecooper wrote:
    This may be a stupid question but how does my Tiagra 9 speed mech work with the 8 speed cassette and shifters? This is as originally supplied on my Specialized Allez. This would suggest that the amount of rear mech movement for each gear change is a function of the STI lever and not the mech.

    I think it's OK to use to a mech with a higher speed rating than the shifters, but not necessarily the other way around.

    e.g. Ultegra rear mech is rated as 8/9/10 speed
    But I wouldn't want to use a 2200 rear mech with 10 speed STIs
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  • aracer
    aracer Posts: 1,649
    davecooper wrote:
    This may be a stupid question but how does my Tiagra 9 speed mech work with the 8 speed cassette and shifters? This is as originally supplied on my Specialized Allez. This would suggest that the amount of rear mech movement for each gear change is a function of the STI lever and not the mech.
    Your last sentence is correct - the geometry of all Shimano indexed mechs (excluding original 8-speed DA, but that's now a historical footnote) is exactly the same, so you can in theory use an 8-speed mech to run 9-speed gears given appropriate shifters.
  • davecooper
    davecooper Posts: 290
    All perfectly clear now, thanks all for the help.

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