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  1. #1
    Si se Puede!!!....Ahuevo! gr23932's Avatar
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    Tiagra RD capacity...

    I know that Shimano states that 27t is the largest cog it can handle but I'm curious if any one has used a 30T or 32T with success. It's on my LHT which I use to haul my two kids around on weekend trips and I must say that I've gotten my @ss kicked a few times on some big hills.
    Ese dicho que me han dicho que tú has dicho que yo he dicho, ese dicho no lo he dicho, porque si lo hubiera dicho, ese dicho estaría bien dicho por haberlo dicho yo.

  2. #2
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by gr23932 View Post
    I know that Shimano states that 27t is the largest cog it can handle but I'm curious if any one has used a 30T or 32T with success. It's on my LHT which I use to haul my two kids around on weekend trips and I must say that I've gotten my @ss kicked a few times on some big hills.
    You can push it to 29 or 30 (good luck on finding a cassette with those as the low gear). Not much further, however. Your best bet would be to ditch the road derailer and go for a mountain bike one. Jenson has an LX for $49. It'll fix all your problems and you'll be able to run a 11-34 cassette.
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  3. #3
    Si se Puede!!!....Ahuevo! gr23932's Avatar
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    Quote Originally Posted by cyccommute View Post
    You can push it to 29 or 30 (good luck on finding a cassette with those as the low gear). Not much further, however. Your best bet would be to ditch the road derailer and go for a mountain bike one. Jenson has an LX for $49. It'll fix all your problems and you'll be able to run a 11-34 cassette.
    Thanks. I think I'm going to try changing just the small chainring first and see if that improves my climbing with the kids in tow.
    Ese dicho que me han dicho que tú has dicho que yo he dicho, ese dicho no lo he dicho, porque si lo hubiera dicho, ese dicho estaría bien dicho por haberlo dicho yo.

  4. #4
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by gr23932 View Post
    Thanks. I think I'm going to try changing just the small chainring first and see if that improves my climbing with the kids in tow.
    The cost of a chainring may be about the same as a new derailer and cassette, depending on what kind of crank you have. And you may only gain a couple of teeth on the chainring. If you have a standard double road crank, the inner ring is probably a 40 or 39. You can't fit anything smaller than a 38 to that bolt ring circle.

    If you have a triple (road), you can drop from a 30 tooth (pretty standard) to a 24 tooth. That makes a pretty good difference. But I don't know if the Tiagra will handle the chain wrap. The LX certainly would.
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  5. #5
    weirdo
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    Cool- I`m glad I ran into this thread because I was kind of wondering the same thing. It sounds like the OP is going with a smaller ring, but for what it`s worth, HG70 comes in 11-30, as do a few level SRAM casettes.

  6. #6
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    I've been doing a bit of research into the same question, as part of my planning out my next bike. I'm looking at getting a cross bike to use as a "jack of all trades commuter/century/group ride bike". Looking at my current gearing (48/38/28 11-32 8sp) and what I use/don't use and planning it around a compact double with a 9sp.

    Currently, in addition to almost never using the 48/11 and 48/13 (and those only on downhills where I could otherwise rest), I find the spacing too wide, with 15%+ jumps between cogs. Also I know that I can climb hills over 9% in my 38/32 (mechanical issues prevented my from shifting to granny on a group ride with a documented climb).

    This gave me an idea that I need gear-inches from ~95 at the high end to 31 at the low end, but with tighter spacing in between. A bit of playing with a gear calculator found a combo that would give me what I want 46/34 with 13-30 9sp. The 13-30 is a custom cassette that Harris Cyclery calls the "Century Special" and claims with work with even short cage derailleurs. This will give me a range of 94.7 to 30.3 (staying with my 700x28 tires) and spacing well under 13% on most shifts.

    To finish off my statement, I'll quote Sheldon Brown on the ratings of capacity of rear derailleurs.

    Rated maximum rear sprocket size, however, is also commonly much lower than what actually works. For instance, Shimano's models designated as "road" derailers are generally listed for a "maximum" sprocket of 27 teeth...because 27 teeth is the largest size that they make in a designated "road" cassette. However, in almost all cases, these derailers, even the short-cage models, will handle rear sprockets as large as 30 teeth in practice. (This somewhat depends on the design of the frame's derailer hanger, so once in a while you will find a particular installation where you can't use a 30, but I've never seen one where a 28 wouldn't work
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  7. #7
    GATC
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    Quote Originally Posted by gr23932 View Post
    Thanks. I think I'm going to try changing just the small chainring first and see if that improves my climbing with the kids in tow.
    I see where you're going, I've been there. Guess what, the kids will grow faster than your conditioning can improve. Try and get a 1:1 gear ratio.

  8. #8
    Si se Puede!!!....Ahuevo! gr23932's Avatar
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    Thanks guys for you input and suggestions. I think I'm going to see if a 11-32 cassette I just got for nothing will work. If it doesn't, I will end up getting a new Rd and granny chain ring.
    Ese dicho que me han dicho que tú has dicho que yo he dicho, ese dicho no lo he dicho, porque si lo hubiera dicho, ese dicho estaría bien dicho por haberlo dicho yo.

  9. #9
    Si se Puede!!!....Ahuevo! gr23932's Avatar
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    Quote Originally Posted by HardyWeinberg View Post
    I see where you're going, I've been there. Guess what, the kids will grow faster than your conditioning can improve. Try and get a 1:1 gear ratio.
    I'm glad I'm not the only one that went through this. I have been able to make every hill I've faced with the kids and panniers but I just want to do it without feeling I got my a$$ handed to me after every big climb. Sounds reasonable??
    Ese dicho que me han dicho que tú has dicho que yo he dicho, ese dicho no lo he dicho, porque si lo hubiera dicho, ese dicho estaría bien dicho por haberlo dicho yo.

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