57.2cm top tube to 57cm top tube - will I notice the difference?
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  1. #1
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    57.2cm top tube to 57cm top tube - will I notice the difference?

    Hi everybody,

    Like many others, I've developed an interest in cross and gravel riding lately. I have been taking my road bike on muddy farm roads and mellow singletrack and have discovered its limits pretty quickly.

    It's an XL (58cm listed size, 57.2 effective top tube) with a 100mm stem and it feels like its sized appropriately for me. It falls about in line with Competitive Cyclist's French Fit guidelines for me (57 to 57.4 ett) and I am looking at a cross bike (XL, 58cm listed size, 57.0 ett) and am wondering if I will feel the difference. I have ridden a bike with a 56cm ett and it was way too small. Have not ridden a bike with a 58cm top tube yet. I may have to try that in the future.

    I feel silly asking about 2mm, but I'd really like to get all of your input on this.

  2. #2
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    Top tube length has very little to do with how a bike fits.

    What if the seat tube angles are vastly different, what then?

    The values you need to match are stack and reach. Find the stack and reach of your current bike and get one that matches. You might find that they have different top tube lengths but the same reach. One might require a setback seatpost and one might require a straight one. What matters is that the reach is the same.
    use a torque wrench

  3. #3
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    Quote Originally Posted by MMsRepBike View Post
    Top tube length has very little to do with how a bike fits.

    What if the seat tube angles are vastly different, what then?

    The values you need to match are stack and reach. Find the stack and reach of your current bike and get one that matches. You might find that they have different top tube lengths but the same reach. One might require a setback seatpost and one might require a straight one. What matters is that the reach is the same.
    Exactly.

    And it might be worth asking yourself if you even want the same fit on a cross bike that you have on your road bike. Personally I prefer a more upright position on a cross bike. Aero is less important and I think being more upright helps with bike handling on the challenging stuff.

  4. #4
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    Quote Originally Posted by Jay Strongbow View Post
    Personally I prefer a more upright position on a cross bike. Aero is less important and I think being more upright helps with bike handling on the challenging stuff.
    I feel that I am very upright on my road bike right now. I like the way it fits and would be happy with a cross bike that is the same.

    I used the gear inches excel sheet to compare reach and bar height and it looks to be extremely close, with the cross bike being 2.4mm lower and 1.9mm shorter.

  5. #5
    hfc
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    I ride 56 and 57 cm road bikes but my cross bike is a 54. I rode a 56 cm Ridley for years which was fine for road and gravel riding but too big for cross racing. Ridleys have a reputation for fitting "bigger" in a given size than other cross bikes however. I guess my point is that a comfortable fit for gravel riding may not be the best fit for cross racing.

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