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Old 05-17-09, 02:21 AM   #1
soulfullspirit
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chain ring sizes

Hi guys i currently have tiagra crank set on my bike i think my smallest ring is a 30 tooth what i want to do is to go to a 22 tooth, can i fit the LX 22 tooth or will i have to buy the whole deore LX crank set?? by the way will this make much difference i have a touring bike with huge load and need lower gears
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Old 05-17-09, 03:30 AM   #2
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Front deraillers have a rated maximum tooth range, as well as a minimum large-middle tooth drop. I think the tooth capacity is usually around 21 or 22 teeth, so assuming you have a 30-39/42-52 crankset, going down to 22 would put you way out of the FD's rated range. I haven't tried so I don't know how conservative that rating is in practice. For what it's worth, my touring bike has a 26-38-48 crankset with a 105 FD, and I imagine if Cannondale could have put a larger range crankset on there that would work well, they would have.

Last edited by ReelExterminato; 05-17-09 at 04:16 AM.
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Old 05-17-09, 05:43 AM   #3
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Know what you have. The Tiagra triple is a 130/74 BCD crankset. The smallest ring possible is a 24. 24 with a 32 or 34 cog gives you a 20 or 19 gear inch low end. That's low enough. A 22 ring will only drop that by 1 gear inch. You won't notice it.

Here's the deal..... a stock Shimano road triple is not very good for touring, it is meant for general road riding in hills, not touring. A 130/74 crank offers 24 as the lowest small ring, 38 the lowest middle ring. What would work would be a 24/38/48 .... or even a 24/44/48... called a half-step pus granny. You could use your existing triple front D for the 24/38/48, but you'd need a double 9 speed or less FD for the half-step+G. Trust me, it just works. Rated capacities on FD's mean next to nothing, from experience. The 105 double I use with 24/44/48 is rated at 15 teeth, yet handles 24 with ease.


You do not need Shimano brand rings. Repeat that, never forget it. There's many brands of 130 BCD rings. Vuelta is among the best bang for the buck rings. All 3 could be had for around $60 if you look.


If you don't want to buy 3 new rings, you could always get the super Sugino XD-600 crankset, sometimes called the XD2 also. www.rivbike.com sells it with touring-ready 24/36/46 rings for $110. You'll need a square taper BB too, $40. Weigh the cost difference. A 46/11 is still a 111 gear-inch top end.


Look up on google about bicycle touring gears if you want to learn a ton.
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Old 05-17-09, 06:36 AM   #4
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Here's the deal..... a stock Shimano road triple is not very good for touring, it is meant for general road riding in hills, not touring. A 130/74 crank offers 24 as the lowest small ring, 38 the lowest middle ring. What would work would be a 24/38/48 .... or even a 24/44/48... called a half-step pus granny. You could use your existing triple front D for the 24/38/48, but you'd need a double 9 speed or less FD for the half-step+G. Trust me, it just works. Rated capacities on FD's mean next to nothing, from experience. The 105 double I use with 24/44/48 is rated at 15 teeth, yet handles 24 with ease.
Interesting. Will that work with an STI front shifter?
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Old 05-17-09, 07:09 AM   #5
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I keep forgetting that most people are using the semi-auto type shifting these days. I'm not real familiar with STI front in actual use, but from reading their tech manuals on STI front shifting, it does allow for fine tuning. I think with a half-step +G you really need a friction mode though. I learned some of what works from here http://www.coinet.com/~beckman/ ..... and re-reading it, he does mention that half-step+G doesn't work with STI or Ergo shifters. Bummer.

For touring set-ups, many people like bar end shifters of course. They have a friction option on the Shimano ones. I use pure friction SunTour ratcheting thumbshifters with Nitto Albatross bars myself. I guess I never grew out it
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Old 05-17-09, 07:10 AM   #6
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As noted, a 24T ring is the smallest that will fit your crank. I've changed the 30T granny for a 26T on many Shimano and even a Campy triple crank and the shifting has been good. The shift to and from the 26T granny isn't quite as good as the 30T but it's more than acceptable.

You will probably loose the ability to use the granny ring with the smallest one or two rear cogs since you will have exceeded the rear derailleur's chain wrap capacity but that is no functional loss.
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Old 05-17-09, 07:20 AM   #7
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Nothing like some feedback Hillrider ! With a low of 26t, that would be a painless option for the OP, as he could retain all the STI. His FD should handle it fine. A 26/32 or 34 still gives a low of 22 or 21, which is still low enough. Riding gears that low .... sometimes you wish you were walkin'
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Old 05-17-09, 07:29 AM   #8
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Riding gears that low .... sometimes you wish you were walkin'
Not really. A 26T granny with a 34T rear cog is a 20" gear (assuming 700c wheels) and at 75 rpm gives you about 4.5 mph. Most people don't walk that fast and certainly not while pushing a loaded bike up a steep hill.
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Old 05-17-09, 01:08 PM   #9
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Not really. A 26T granny with a 34T rear cog is a 20" gear (assuming 700c wheels) and at 75 rpm gives you about 4.5 mph. Most people don't walk that fast and certainly not while pushing a loaded bike up a steep hill.
Well... yes and no. I have a 24/34 low gear that I used on a steep (maybe 20%) climb while carrying a touring load. My wife was behind me, also loaded, and she was about as fast walking and pushing. I got a gap on her when we got to the top of the hill and I rode away while she had to pause and remount.
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