Little advice from the experts please...- Mtbr.com
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  1. #1
    Tonic Fall Guy
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    Little advice from the experts please...

    Hi
    I'm new here and, I must say, super pumped to find such a great resource for bike info and advice!

    Anyway, I have a Bianchi SASS 17.5" (https://www.bianchiusa.com/05-bicycl.../05-sass.html). I use it to crank on trails and all over the city. Right now winter's coming and I'd like to convert this into more of a commuter.

    So, this bike has 32T in the front and 16T in the back, but the Truvativ crankset in the front seems built to be only at 32T. IE, I couldn't expand the teeth number because it's built in with the chainguard. I want the bike to be faster for flatland commuting -- no hills, really. Can I just make the rear cassette bigger? Also, I'll be putting slicks on the bike so I'm guessing (sorry, pretty new to mechanics on bikes) with less friction the bike will really just spin out pretty hard at the current ratio. Any advice here? Thanks for reading and I apologize for any misusage of terms here. Thanks!

  2. #2
    General industry guy
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    Hmmm, tried to post just a second ago and the server was too busy. If the message pops up later, sorry for the duplicate.

    Anyway, you can change the chainring (the front chainwheel) on your bike. The bashguard and the chainring are simply bolted, with the same bolts, to the same part of the crankset. You can remove the bolts and replace the ring with a larger one; the bashguard won't be the correct size, but that's okay, you can just remove it.

    You can also change the rear cog to a smaller one to have harder/faster gearing. Smaller rear/larger front for harder/faster; larger rear/smaller front for easier/slower. Try a 36 tooth ring with your current cog, or if that's too easy, try a 36x15 combo. Good luck!
    Alison Dunlap Coaching
    When you're not paid to ride.

  3. #3
    Tonic Fall Guy
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    Thanks Joey. I think I would like to find a way to keep the bashguard (though I could probably buy a larger one to accomodate a larger chainring up front. So increasing the size of the rear cog won't make my bike faster on the flats?

  4. #4
    WWYD?
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    Check your BCD first. It is the imaginary circle that runs around all the center of the chainring bolt holes in your chainring. Lay a ruler across your crank to find the actual diameter of this, it's probably 110 mm.

    Right now I'm running a 39 tooth (39X16) for my Monocog commuter and using a converted double road crank and the ring in the outer position. If you want anything bigger in teeth you will probably need a new crank and possibly a wider bottom bracket so the teeth will clear the frame.

    Be careful about using a smaller gear in the back, you might not have enough chain wrapping the rear gear and it will slip when you put a lot of torque down on the pedals.

  5. #5
    Tulsa
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    aren't truvative usually 64/104?
    wherever you go, there you are

  6. #6
    WWYD?
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    Quote Originally Posted by rojogonzo
    aren't truvative usually 64/104?
    Probably, I'm using an RPM crank

  7. #7
    Feeling retro..but Jung
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    smaller

    Quote Originally Posted by crashwins
    Thanks Joey. I think I would like to find a way to keep the bashguard (though I could probably buy a larger one to accomodate a larger chainring up front. So increasing the size of the rear cog won't make my bike faster on the flats?

    Smaller rear cog = Faster in the flats..

  8. #8
    Ovaries on the Outside
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    First thing you need to understand is that a larger chainring (front) and/or smaller cog (back) will make you travel further with each pedal stroke. There are different ways of measuring this, and I typically go with gear inches- definition here. The higher the gear inches, the further you are traveling in a pedal stroke. For road, I lean towards 70ish gear inches, which for you might be 38x15. You can calculate gear inch combos here.

    You might have the drop the bashguard to put a larger chainring on. It might hit the chainstay on the inside position.

  9. #9
    mtbr member
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    You can also calculate gear ratios here. As well as gear inches, gain ratios, development, and skid patches. Similar to Sheldon's, but you get all of the information simultaneously.

    And moving the chainring to the outer position does not mean losing the bashguard. It just means you may have to obtain slightly longer receivers and use some spacers to stack the bg against the cr. It is not imperative that the bashguard interface with the flats on the spider.

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