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  1. #1
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    Tire size makes a difference in gear inches...

    Just now starting to realize this, as well as getting confirmation via Sheldon Brown's gear calculator.

    Right now, I have 170 cranks, 36/20 with a 1.9 rear (26")...

    I plan to upgrade to 175 cranks, 32/18 with a 2.0 tire (26")...

    ...gear inches nearly match, but I get a slightly plusher ride in the rear.

    Thank God I can use whatever I want on the front and it doesn't affect the gearing, because I can go bigger (2.35) to plush up my steel fork.

    Anyhow, I should've figured this out sooner - could have saved me a lot of headache.

  2. #2
    trail rat
    Reputation: slocaus's Avatar
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    One more compliconfusion point is that the stated tire size is width and not all 1.9 tires are 1.9 and not all 2.35 are 2.35, ad nauseum. Annnnnnd, the height can vary within the same size. I have some 2.2 tires that are much taller than the 2.4 tires I have used. So unless you do circumference roll outs, you calcs will still be guesstimations and likely different from real reality.
    "The physician heals, Nature makes well" - real fortune cookie

    CCCMB trail work for trail access - SLO, CA

  3. #3
    Out spokin'
    Reputation: Sparticus's Avatar
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    Quote Originally Posted by slocaus View Post
    ... real reality.
    Please define the other kind.

    --sParty
    disciplesofdirt.org

    We don't quit riding because we get old.
    We get old because we quit riding.

  4. #4
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    What about psi and spoke tension? BB spindle length?

  5. #5
    trail rat
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    Quote Originally Posted by Sparticus View Post
    Please define the other kind.

    --sParty
    Virtual reality, which I am too old to really get a grasp on, probably partially because of the fact that I was in college in the 60's when we had

    Altered reality, and that is pretty fuzzy too.......

    'If you remember the '60s, you weren't there'? - Robin Williams

    Quote Originally Posted by p nut View Post
    What about psi and spoke tension? BB spindle length?
    Psi will be accounted for in roll out circumference. I don't grasp how spoke tension or BB spindle length affects gearing though. 'splain it?
    "The physician heals, Nature makes well" - real fortune cookie

    CCCMB trail work for trail access - SLO, CA

  6. #6
    one chain loop
    Reputation: fishcreek's Avatar
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    how about the dirt on the tire. and mud on the pedals.
    everything sucks but my vacuum cleaner.

  7. #7
    Ovaries on the Outside
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    Quote Originally Posted by slocaus View Post
    Psi will be accounted for in roll out circumference. I don't grasp how spoke tension or BB spindle length affects gearing though. 'splain it?
    I think it was a joke, though I am pretty sure my gear inches are wicked different when I have a flat.

    I don't think that tire size matters that much. I don't notice a difference from one to the other as much as I notice the difference between gripping and slick mud. Is there a calculator for that? Cause during our 12 month winter we're having in Orygun, I've averaged about 10 inches of forward movement for a full crank rotation, which should feel easier than it does.

  8. #8
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    I've noticed when I went from a 1.9 to a 2.35. I don't think it will be much from a 1.9 to a 2.0, though.

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