Run a 28t 1x10 with 104 BCD Crank- Mtbr.com
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  1. #1
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    Run a 28t 1x10 with 104 BCD Crank

    I just ordered the Hope 40T-Rex for my Shimano cassette and am going to go from 2x10 to 1x10. To keep the gearing ratio close to what I had, which was 22/36 up front, I would like to run a 28t up front. However, my crank is 104BCD and the smallest ring I can run is 30t. Is there any way to convert down to a 28t using a spider or bash guard, anything? At some point I will probably replace the crankset with a direct mount one, but would prefer if I didn't have to do that right now.

  2. #2
    All fat, all the time.
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    30T is the smallest with a 104BCD spider type crank....

    It'll make you stronger

    Your other option is do 30T and add a 42T in the back.

  3. #3
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    Run a 28t 1x10 with 104 BCD Crank

    There is a company that makes custom chainring my dad said when he was looking. I would like a 28t as well. I wonder if there is a reason raceface and wolftooth don't make it in that bcd? Maybe it just doesn't fit with the n/w profile or something.

    I will try and find the name of the company.
    This is quite interesting to me as a bike geek. I am sure you all will enjoy it as well.

    http://www.popsci.com/technology/art...ycle-go-80-mph

  4. #4
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    30T from Wolftooth up front and a 42T from one-up components at the rear. ... all you need !

  5. #5
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    Run a 28t 1x10 with 104 BCD Crank

    It's hard to factor in the math with fat tires. Does 30t and 42t rear come close to a 22t and 36t rear combo?

  6. #6
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    Second question in relation to my issue. Can you run the bash guard inside of the crank. All of the pictures I've seen show the bash guard on the outside of the crank, but my crank doesn't have the notches by the bolts for the bash guard to sit on. So would it be ok to go on the inside?

  7. #7
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    Yes, it's the same. Unfortunately the Hope 40T-Red is already here, but what's another $90

  8. #8
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    Do your cranks have 64bcd on them as well? If so, you could always use one of these:

    Widgit for 2 ring crankset | Widgit

  9. #9
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    Run a 28t 1x10 with 104 BCD Crank

    Another option that I'm going to go with on my Lurch is the Absolute Black 64BCD which comes in 26, 28, &30T.

    https://www.absoluteblack.cc/xx1-style-shimano.html

  10. #10
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    Quote Originally Posted by Ufdah View Post
    Another option that I'm going to go with on my Lurch is the Absolute Black 64BCD which comes in 26, 28, &30T.
    Hopefully the larger ring will clear the chainstay in the 64BCD granny position.

  11. #11
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    Run a 28t 1x10 with 104 BCD Crank

    They warn of the 30T but say the 26 & 28 should be OK.

  12. #12
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    Quote Originally Posted by tundratrader View Post
    It's hard to factor in the math with fat tires. Does 30t and 42t rear come close to a 22t and 36t rear combo?
    Sheldon brown gear calculator will give you all the math you need. Just tell it to use a 29er tire, and it'll be pretty close to the outside diameter of a fatty.

    I use a 29tooth on the small ring location on my cranks. Just had to adjust the chain line out by moving the bottom bracket spacers.

  13. #13
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    Run a 28t 1x10 with 104 BCD Crank

    Here's what Absolute Black says about the 64BCD Narrow Wide Rings:
    26/28/30T - Please note this size is in 64BCD! It provides a lot better chainline that way (around 44mm) for using granny gears. That means no rubbing while riding uphill and less drivetrain wear. Chainline will be on 6th cog from smallest on 10spd cassette. 3X crankset users, please be mindful that 30T ring may touch chainstay if not enough space, so please check(or send us a photo). 26/28T will fit to all cranks. 2X crankset users will accommodate 26/28/30T ring with easy.

  14. #14
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    Quote Originally Posted by tundratrader View Post
    It's hard to factor in the math with fat tires. Does 30t and 42t rear come close to a 22t and 36t rear combo?
    No, it is not close at all:

    30/42=71.5%
    22/36=61.1%

    You'd need to go all the way down to a 26t chainring to get close:

    26/42=61.9%
    --Peace

  15. #15
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    I found this. Put a Blackspire Granny Gods bash guard in place of the 36t ring.
    Blackspire - Granny Gods | Blackspire

    And replace the 22t ring with a 26t narrow/wide 64 BCD from absolute black
    https://www.absoluteblack.cc/xx1-style-shimano.html

    However, I see absoluteblack has a ring for Shimano and one for SRAM. I have a Shimano cassette and a SRAM x7 RD. So should the chainring match the rd or the cassette?

  16. #16
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    Quote Originally Posted by lhovden View Post

    However, I see absoluteblack has a ring for Shimano and one for SRAM. I have a Shimano cassette and a SRAM x7 RD. So should the chainring match the rd or the cassette?
    I think you are misreading something. Chainrings are not shimano/sram specific as far as I can tell. Cogs normally are and should match the rest of the cassette.
    --Peace

  17. #17
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    What do you think the difference is when it gives you a sram and shimano option?

  18. #18
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    Second question. My crank arms don't have tabs that a bash guard normally rests on, see image.

    Name:  specialized_fatboy_crank.jpg
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    Almost all of the pictures of bash guards I've seen show the guard on the outside of the crank arm resting on those tabs. If I don't have the tabs will a bash guard work on the inside like a normal chainring? Or will that get too tight to the little chainring and chain?

  19. #19
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    A thin one like BBG might fit on the inside in place of the big ring.

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