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  1. #1
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    new chaingring for shimano 105 trek 520

    after my first tour, i know understand the need for the smallest small chainring money can buy! i have a trek 520 with a shimano 105 crank (52/40/30), shimano 105 FD, Shimano Deore LX RD and SRAM PG970 11-32, 9 speed cassette. instead of swapping out the whole crank, i'm thinking of just replacing the small chainring with a 26 for when i'm climbing.

    two questions. first, will this work/is it possible? second, where can i purchase a 26 tooth chainring for my 105 crank/i don't see anything online?

    thanks.

    jeff

  2. #2
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by jignall View Post
    after my first tour, i know understand the need for the smallest small chainring money can buy! i have a trek 520 with a shimano 105 crank (52/40/30), shimano 105 FD, Shimano Deore LX RD and SRAM PG970 11-32, 9 speed cassette. instead of swapping out the whole crank, i'm thinking of just replacing the small chainring with a 26 for when i'm climbing.

    two questions. first, will this work/is it possible? second, where can i purchase a 26 tooth chainring for my 105 crank/i don't see anything online?

    thanks.

    jeff
    You can probably go down to a 24 tooth if it's a 74mm BCD ring. If it's a 5 bolt crank should be able to put any 5 bolt 74mm BCD ring on it. Bikeman has Race Face for $23.
    Stuart Black
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  3. #3
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    Quote Originally Posted by cyccommute View Post
    You can probably go down to a 24 tooth if it's a 74mm BCD ring. If it's a 5 bolt crank should be able to put any 5 bolt 74mm BCD ring on it. Bikeman has Race Face for $23.
    Thanks for the feedback. Not sure I understand your terminology of a "74mm BCD ring"? How do I check this?

  4. #4
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by jignall View Post
    Thanks for the feedback. Not sure I understand your terminology of a "74mm BCD ring"? How do I check this?
    BCD = bolt circle diameter. Here's how to figure it.
    Stuart Black
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    Twisting Down the Alley. Misadventures in tornado alley.
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    I put a 26 on my 105, got it at a bike shop, it was some brand that started with a "v". It doesn't have to be anything fancy (ramps & pins) since it's friction shifting.

    If you go to a 24, there are a couple of different kinds of thingies that keep your chain from popping off to the inside, "third eye chain watcher" or something like that - might be helpful. I have one of these on my current rig (mtb gearing).
    ...

  6. #6
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by valygrl View Post
    I put a 26 on my 105, got it at a bike shop, it was some brand that started with a "v". It doesn't have to be anything fancy (ramps & pins) since it's friction shifting.

    If you go to a 24, there are a couple of different kinds of thingies that keep your chain from popping off to the inside, "third eye chain watcher" or something like that - might be helpful. I have one of these on my current rig (mtb gearing).
    The problem I had on a 135 mm BCD crank with a 24 tooth inner was the chain would sometimes wedge in between the inner ring and the middle ring. There's a pretty big gap there. It didn't happen often but it's very annoying...and a little difficult to extract the chain...when it does it.
    Stuart Black
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    Twisting Down the Alley. Misadventures in tornado alley.
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  7. #7
    ...into the blue...
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    Quote Originally Posted by cyccommute View Post
    The problem I had on a 135 mm BCD crank with a 24 tooth inner was the chain would sometimes wedge in between the inner ring and the middle ring. There's a pretty big gap there. It didn't happen often but it's very annoying...and a little difficult to extract the chain...when it does it.
    I had the same problem. This taught me to shift well before the uphill started. This was back when I was still getting used to my new speedplays as well :-)

  8. #8
    Senior Member BengeBoy's Avatar
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    Re-gearing my used 520?

    I'm looking at lowering the gearing on the used 2006 Trek 520 that I purchased recently (love the bike, and the gearing is fine for around-town riding and commuting, but I want to lower the gearing before trying loaded touring in the mountains).

    I wanted to get the crankset down to gears in the neighborhood of 24/26/48, or even lower.

    I was looking at the TA chainrings on Peter White's website but it gets pretty spendy to replace all 3...it would be something like $150 to $160 to put 3 new chainrings on my bike.

    I had not thought about RaceFace until I saw this thread here - 3 new RaceFace chainrings would run about $110.

    Or, I could get a whole new crankset. Other folks on this forum have recommended a Shimano XTR crankset; the Shimano Deore XT M770 Crankset at bikeman.com would be $270.

    Still others have recommended the Sugino XD600, which runs about $80 at bikeman (wouldn't I also need a new bottom bracket for this?).

    That gives 4 options:
    1. Replace stock chainrings with TA
    2. Replace stock chainrings with RaceFace
    3. Put on a new Shimano mountain bike crankset, like the Deore XT
    4. Put on a new Sugino XD 600.


    I'm a little confused on which of these would be best...one advantage I see to switching out the crank is then I could sell my stock Shimano 105 crank...if I went to the trouble of selling that I'm guessing the cost would comparable...

    Any opinions?

  9. #9
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by BengeBoy View Post
    I'm looking at lowering the gearing on the used 2006 Trek 520 that I purchased recently (love the bike, and the gearing is fine for around-town riding and commuting, but I want to lower the gearing before trying loaded touring in the mountains).

    I wanted to get the crankset down to gears in the neighborhood of 24/26/48, or even lower.

    I was looking at the TA chainrings on Peter White's website but it gets pretty spendy to replace all 3...it would be something like $150 to $160 to put 3 new chainrings on my bike.

    I had not thought about RaceFace until I saw this thread here - 3 new RaceFace chainrings would run about $110.

    Or, I could get a whole new crankset. Other folks on this forum have recommended a Shimano XTR crankset; the Shimano Deore XT M770 Crankset at bikeman.com would be $270.

    Still others have recommended the Sugino XD600, which runs about $80 at bikeman (wouldn't I also need a new bottom bracket for this?).

    That gives 4 options:
    1. Replace stock chainrings with TA
    2. Replace stock chainrings with RaceFace
    3. Put on a new Shimano mountain bike crankset, like the Deore XT
    4. Put on a new Sugino XD 600.


    I'm a little confused on which of these would be best...one advantage I see to switching out the crank is then I could sell my stock Shimano 105 crank...if I went to the trouble of selling that I'm guessing the cost would comparable...

    Any opinions?
    Even better then the Sugino is the Shimano Trekking crank from Nashbar. The current price is $80 but the price has fluctuated as low as $45. Keep an eye on it.

    It will take a smaller inner ring than the Sugino. Shimano also makes a version of this with external bearings which is about the same as the mountain bike crank but external bearings are super simple to work on in the field and easier to install. If you have the money, they might be worth it.
    Stuart Black
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    Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
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  10. #10
    Senior Member BengeBoy's Avatar
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    The version you're referring to with external bearings; is that the Shimano LX FC-M580 Crankset, also at Nashbar?

    If I have a Shimano 105 already installed on the bike, can I just switch to the new Crankset, or will I also have to get a new bottom bracket?

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