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  1. #1
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    Help with Shimano Tiagra Rear Derailleur capacity

    I have a 2011 Salsa Casseroll with a Shimano Tiagra-GS cage rear derailleur. As delivered, it has a triple up front (26,36,48) with a rear cluster of 12-25. Great fun ride for day rides, I love the closely spaced gearing. However, thinking I may use this bike for a CC tour, and I'd like to have some lower gearing. Shimano's documents on the rear Tiagra indicates a 22 tooth range for the front and a max of a 27 tooth on the rear.

    I'm wondering if anyone has pushed the rear to a 11-30 cluster? If I don't cross shift the gearing will the rear derailleur handle it? Or should I look to change the front to a 24,36-46 set? Still not as low as I'd want though unless I get a rear derailleur that has the max 27.

    Thanx's
    1965 Moulton Speed 4, 1974 Fuji 12 speed, 1987 DB Ascent EX, 2006 Dahon Speed TR, 2009 Salsa Fargo, 2011 Gravity 29.4, 2011 Salsa Casseroll, 2012 Surly Moonlander

  2. #2
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    I have a long cage(SGS?) on my touring bike with 20-34-46------14-34.It won't cross chain the small small without slack in the chain,but who does that anyways.

    My old Shimano 600,which by todays standards would be a med cage(GS?),would handle it,I just wore it out.
    Last edited by Booger1; 03-21-12 at 09:36 AM.
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  3. #3
    coprolite fietsbob's Avatar
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    SGS is the longer cage, GS a bit shorter, FYI.

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    Quote Originally Posted by fietsbob View Post
    SGS is the longer cage, GS a bit shorter, FYI.
    The GS cage is a mid cage I believe and is more road oriented. I may just have to order a cassette and give it a try. The Casseroll drivetain seems to be a mix, what with the low triple up front. It also uses brifters, so I think that may limit the derailleur choices. Harris Bicycle in Boston has a custom 13-30 cassette, expensive but I may give it a try since it appears to be design with what I want. close spacing in the high gears and some low gears at the other end. All of which are nicely spaced.
    Last edited by VT_Speed_TR; 03-21-12 at 10:53 AM.
    1965 Moulton Speed 4, 1974 Fuji 12 speed, 1987 DB Ascent EX, 2006 Dahon Speed TR, 2009 Salsa Fargo, 2011 Gravity 29.4, 2011 Salsa Casseroll, 2012 Surly Moonlander

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    For the price of one those Harris Cyclery cassettes, you can buy a 13-32 off-the-shelf cassette and a mountain RD (with an SGS cage) and be assured that you can reach the 32t sprocket as well as pull enough chain slack. The Tiagra RD only pulls 37t while a mountain RD pulls 45t. Your brifters will still work.

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    Senior Member Doug64's Avatar
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    pexio
    For the price of one those Harris Cyclery cassettes, you can buy a 13-32 off-the-shelf cassette and a mountain RD (with an SGS cage) and be assured that you can reach the 32t sprocket as well as pull enough chain slack. The Tiagra RD only pulls 37t while a mountain RD pulls 45t. Your brifters will still work
    +1

    However, why not go for an 11-34, and give yourself a broader range of gears?

    I tried one of Harris's 13-30 with a Shimano 105 LC rear derailleur, and I could not make it work to my satisfaction. I replaced the 30 tooth cog with a 11 tooth cog, and put it on my road bike. It gave me an 12-27. It is an Ultergra cassette, and that was a good use for it.

    After talking to the folks at Harris, they sent me the 12 tooth cog at no extra cost.

    The way they build the 13-30 cassette is to add a spacer and 30 tooth cog, and remove the 12 tooth cog from the stack of a stock 12-27 Ultegra cassette. the first 3 or 4 cogs are loose, while the rest are affixed to a carrier. The 30 tooth cog is just loose and is separated from the carrier by a spacer as you install the cogs. It is a cog from a low end cassette that was bolted or riveted together rather than using a carrier.

    Last edited by Doug64; 03-22-12 at 11:25 AM. Reason: Correct the number of teeth

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    I have a Tiagra RD on my Surly Crosscheck (not sure which variation of Tiagra, it's the stock for 2005). I added a 22 tooth front chain ring and changed the cassette out to 11-32. I've put thousands of miles on it since then with no problems.
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    Quote Originally Posted by hopperja View Post
    I have a Tiagra RD on my Surly Crosscheck (not sure which variation of Tiagra, it's the stock for 2005). I added a 22 tooth front chain ring and changed the cassette out to 11-32. I've put thousands of miles on it since then with no problems.
    May just need to "flip" the logic and do what you indicated. Much easier to just swap to a smaller chainring in front. I think I have a 24 in the parts bin, but a 22 would be even better.
    1965 Moulton Speed 4, 1974 Fuji 12 speed, 1987 DB Ascent EX, 2006 Dahon Speed TR, 2009 Salsa Fargo, 2011 Gravity 29.4, 2011 Salsa Casseroll, 2012 Surly Moonlander

  9. #9
    Have bike, will travel Barrettscv's Avatar
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    Quote Originally Posted by VT_Speed_TR View Post
    I have a 2011 Salsa Casseroll with a Shimano Tiagra-GS cage rear derailleur.

    I'm wondering if anyone has pushed the rear to a 11-30 cluster? If I don't cross shift the gearing will the rear derailleur handle it? Or should I look to change the front to a 24,36-46 set? Still not as low as I'd want though unless I get a rear derailleur that has the max 27.

    Thanx's
    I used a Sram 11-32 cassette with a Shimano "GS" (long arm-road) rear derailleur last year and had no issues with a 32 size cog. Fitting a 12-30 should not be a problem.

    Also, the Shimano "GS" (long arm-road) rear derailleur also has huge chain wrap and cog size capacity that is much greater than stated on the Specifications.

    The chain-wrap limit of the Tiagra/105/Ultegra GS, according to Shimano, is 37. I'm operating safely, with every gear combination, using a chain-wrap value of 42. It is also possible to exceed the 27t Cog size capacity and use a 32t. I've combined a 50, 39 & 26 Crankset with the 10 speed Tiagra 12-30 cassette.

    The practical chain-wrap capacity, with a correct length chain, of the road "GS" RD allows the big-big combination of 50t front Chainring & 30t rear cog with a little safety margin and also allows the small-small combination of 26t & 12t without any slack in the chain.



    I'm also using a Shimano "GS" (long arm-road) rear derailleur with a 48, 36 & 22t triple with a 12-27 cassette with no problems. I'm sure a the 12-30 Century special from Harris would also work on this drivetrain.

    Last edited by Barrettscv; 03-22-12 at 09:22 AM.
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  10. #10
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    Quote Originally Posted by Barrettscv View Post
    I used a Sram 11-32 cassette with a Shimano "GS" (long arm-road) rear derailleur last year and had no issues with a 32 size cog. Fitting a 12-30 should not be a problem.

    The Shimano "GS" (long arm-road) rear derailleur also has huge chain wrap and cog size capacity that is much greater than stated on the Specifications.

    I've combined a 50, 39 & 26 Crankset with the 10 speed Tiagra 12-30 cassette.

    The chain-wrap limit of the Tiagra/105/Ultegra GS, according to Shimano, is 37. I'm operating safely, with every gear combination, using a chain-wrap value of 42. It is also possible to exceed the 27t Cog size capacity and use a 32t.

    The practical chain-wrap capacity, with a correct length chain, of the road "GS" RD allows the big-big combination of 50t front Chainring & 30t rear cog with a little safety margin and also allows the small-small combination of 26t & 12t without any slack in the chain.
    This is great to hear. I think I may just spend the $25/$30 for an 11-30 cassette that I found on sale and give it a try. But from your experience it sounds like my original thoughts were correct, the Shimano listed limits in their tech doc's are on the conservative side. I also have a 24 chainring on another bike with a Jump-Stop that I could switch over to get the gearing even lower. I love the close gearing on the Casseroll, but if I'm going to load 10-15 lbs on it and do a CC tour, I just want a little safety margin for spinning up hills.
    1965 Moulton Speed 4, 1974 Fuji 12 speed, 1987 DB Ascent EX, 2006 Dahon Speed TR, 2009 Salsa Fargo, 2011 Gravity 29.4, 2011 Salsa Casseroll, 2012 Surly Moonlander

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