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  1. #1
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    Largest inner ring to outer ring jump?

    I got a 28-34-46 Sugino crankset. I'm looking to just skip the 34 and leave it 28-46. That's a 18 teeth jump. Is that doable?

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    Assuming the crank has 110/74 mm bolt circles, you can't mount the 28T ring as the inner ring of a double since a 34T (ok, 33T) ring is the smallest that will fit on a 110 mm bcd. If you just remove the 34, you will have a huge gap between the 46 and the 28 unless you remount the 46 on the inside of the spider. You will also need single rings chainring bolts.

    The 18T jump is doable with a MTB front derailleur but probably won't be real smooth.

  3. #3
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    Quote Originally Posted by mrbubbles View Post
    I got a 28-34-46 Sugino crankset. I'm looking to just skip the 34 and leave it 28-46. That's a 18 teeth jump. Is that doable?
    It used to be very common to use "half step" gearing on touring bikes - have a decently small small chainring, then a relatively large middle and a relatively small large... If I recall correctly, something like 28-42-46 might work for you. This gives you lots of room to fine-tune your cadence with your two 'large' rings, and you still have the granny when you need it. Also makes shifting between the middle and the large very smooth.

  4. #4
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    Quote Originally Posted by HillRider View Post
    Assuming the crank has 110/74 mm bolt circles, you can't mount the 28T ring as the inner ring of a double since a 34T (ok, 33T) ring is the smallest that will fit on a 110 mm bcd. If you just remove the 34, you will have a huge gap between the 46 and the 28 unless you remount the 46 on the inside of the spider. You will also need single rings chainring bolts.
    Already done that. 28 on the inner, 46 on the middle.


    Quote Originally Posted by HillRider View Post
    18T jump is doable with a MTB front derailleur but probably won't be real smooth.
    I can live with that. Once I get a crank remover, I'll try this out.

  5. #5
    Senior Member Bill Kapaun's Avatar
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    As mentioned, it should work, but shift quality will be less than ideal. You may tend to drop the chain more frequently too.

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    Quote Originally Posted by LarDasse74 View Post
    It used to be very common to use "half step" gearing on touring bikes - have a decently small small chainring, then a relatively large middle and a relatively small large... If I recall correctly, something like 28-42-46 might work for you. This gives you lots of room to fine-tune your cadence with your two 'large' rings, and you still have the granny when you need it. Also makes shifting between the middle and the large very smooth.
    I had just about that exact half-step w/granny combination on an '85 Bridgestone. My rings were 46/42/26 with a 13x28 6-speed freewheel. There were nearly no duplicate gears in the entire range.

    What has made half step gearing obsolete these days is two factors:

    1. In the days of 5 or 6-speeds wide range freewheels had huge gaps between gears. The half-step chainrings split these gaps and gave many more gear choices. Now with 8, 9 or 10 cogs the gaps are quite narrow so the need for half steps is minimized.

    2. Older front derailleurs had rather shallow inner plates and would clear a middle ring almost the same size as the outer ring. Modern indexing front derailleurs have much deeper inner cage plates and would have to be set excessively high to clear the inner ring if it had less than a 10 tooth difference.

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