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Tiagra 9spd triple RD capacity

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Tiagra 9spd triple RD capacity

Old 10-01-18, 05:09 PM
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TrojanHorse
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Tiagra 9spd triple RD capacity

Does anybody know what size cassette I can stick on the back of a tiagra 9 speed triple? The largest cog now is a 26 and my wife is displeased with the effort it takes to get up a hill... and we have plenty around my house.

I've seen 12-27 cassettes but I don't know that 1 tooth is worth the effort/money. The B-screw doesn't look like it leaves much room for a larger cassette as it is. I'd be willing to try a 28 but they appear to be as rare as hen's teeth.

Option B is to maybe find a smaller front chainring, I haven't investigated that. I'm trying to avoid a complete drive train swap out, but it's a possibility.
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Old 10-01-18, 07:34 PM
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Switching to a 27T is not going to help much. There are 13x30 and 12x30 cassettes available from Harris Cyclery and the 30T will make a noticeable difference. Your rear derailleur should handle it. These aren't cheap but less expensive than a drivetrain replacement.

An alternative is to fit an inexpensive 9-speed era MTB rear derailleur and that opens up the world of XXx32, XXx34 and even larger big cogs.

Last edited by HillRider; 10-01-18 at 07:43 PM.
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Old 10-01-18, 07:47 PM
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I didn't think of Harris - I'll try that out. 12x30 would probably be perfect.
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Old 10-01-18, 08:03 PM
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IRD also make a 9-speed 12-30 Shimano-compatible cassette: https://www.sjscycles.co.uk/cassette...gecurrency=USD
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Old 10-01-18, 08:20 PM
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Originally Posted by TrojanHorse View Post
I didn't think of Harris - I'll try that out. 12x30 would probably be perfect.
I suggest you look at this thread-
Advice on building a custom 9-speed cassette?
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Old 10-02-18, 07:39 PM
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Well, heck. I found a Sora HG50 11-30 cassette at chain reaction for about $22, so it's on the way. Low expense if it doesn't work, that's for sure. Harris wanted about $100 for one of their "custom" cassettes. Thanks for the tips.
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Old 10-03-18, 11:57 AM
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Not only are IRD cassettes expensive, but they are also heavy, really heavy.
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Old 10-05-18, 11:20 AM
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Originally Posted by TrojanHorse View Post
Well, heck. I found a Sora HG50 11-30 cassette at chain reaction for about $22, so it's on the way. Low expense if it doesn't work, that's for sure. Harris wanted about $100 for one of their "custom" cassettes. Thanks for the tips.
Harris was putting together and selling 30t big-cog cassettes for around $100, as you say, before they became a standard Shimano-issued item.
I bought one from them, because on their site Sheldon Brown said the Shimano 105 rear derailers were listed as a max 28-tooth, but could handle 30-tooth, which I found to be true.
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Old 10-05-18, 02:14 PM
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STI road triple are typically 53,39,30 ctranks, so RD cage should be medium not short.

how far apart are the pulleys?

they ate foe wrapping up difference of 53 minus 30 , assuming you don't cross chain

30:11 or 53 and your biggest cassette cog.



....
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Old 10-06-18, 06:07 AM
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I've done a lot of that kind of conversion. One or 2 teeth on the rear cassette isn't going to be enough.

I install a Deore rear derailleur and a mountain bike cassette. The road bike 9-speed shifter indexes fine and the 34 tooth rear cog will give enough advantage for her to definitely feel it. You'll also need a new, longer chain. If it makes the difference between a bike that's enjoyable to ride and one that makes her dread every hill, it's well worth the cost.
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Old 10-07-18, 08:35 AM
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If the crank can take any 74bcd inner ring you can probably drop down from the standard 30 to a 28 or even 26. I have a road triple with a 24 tooth inner ring and it works well for steep stuff.
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