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  1. #1
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    Does tire width affect wheel diameter? More....

    I have wheels that are ‘intended’ for 25mm tires.

    The manufacturer, with whom I communicate, advocated putting 23mm tires on them. So I did.

    Maybe I’m just imagining it, but it seems to me that the total circumference of the wheel (with the tire on it) is less than that of a 23mm wheel fitted with a 23mm tire. Specifically, there is less tire height protruding beyond the edge of the rim. Mathematically, this is to be expected, as the tire is more stretched out width-wise at the expense of height.

    But I’m wondering: is this a known/commonplace observation when fitting narrower tires to wider rims.... even when the sizing discrepancy is just 2mm?

  2. #2
    .je
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    There's a thread like yours here: 23mm on 25mm rims

    Without tires and wheels to measure, here is a helpful image:

  3. #3
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    I'm thinking you worded this question backwards, but I get what you're asking.

    The diagram .je posted explains it well. Think of it this way. Take a sheet of paper and roll it into a tube. Now open that tube so the ends are further apart. Notice that the tube diameter becomes larger overall!

    Absolutely no reason to put narrower tires on those rims unless the 25mm tires will no longer fit because the clearances are too narrow. In that case, you will have to use 23mm tires.
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



  4. #4
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    Quote Originally Posted by Waspinator View Post
    I have wheels that are ‘intended’ for 25mm tires.

    The manufacturer, with whom I communicate, advocated putting 23mm tires on them. So I did.

    Maybe I’m just imagining it, but it seems to me that the total circumference of the wheel (with the tire on it) is less than that of a 23mm wheel fitted with a 23mm tire. Specifically, there is less tire height protruding beyond the edge of the rim. Mathematically, this is to be expected, as the tire is more stretched out width-wise at the expense of height.

    But I’m wondering: is this a known/commonplace observation when fitting narrower tires to wider rims.... even when the sizing discrepancy is just 2mm?
    First of all, declaring that a given wheel is "intended" for 23 or 25 mm tires is a bit of a joke. People use a wide range of tire sizes on any given rim and 2mm difference is pretty insignificant. The only thing for certain is that wider rims will result in a wider measurement once the tire is mounted. Whether the tire is taller or not will depend on the specific tire/rim combination.

  5. #5
    tlg
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    Quote Originally Posted by Lombard View Post
    Absolutely no reason to put narrower tires on those rims unless the 25mm tires will no longer fit because the clearances are too narrow. In that case, you will have to use 23mm tires.
    I can think of one...
    After switching to 25mm rims, I have an inventory of 23mm tires to use up.
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  6. #6
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    Quote Originally Posted by tlg View Post
    I can think of one...
    After switching to 25mm rims, I have an inventory of 23mm tires to use up.
    You will just have to sell them on eBay to somebody who didn't read this thread.
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



  7. #7
    tlg
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    Quote Originally Posted by Lombard View Post
    You will just have to sell them on eBay to somebody who didn't read this thread.
    Ha! I got them so cheap, I'd have to do that at a loss. I'm too friggin cheap for that.
    Custom Di2 & Garmin/GoPro mounts 2013 SuperSix EVO Hi-MOD Team * 2004 Klein Aura V

  8. #8
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    Quote Originally Posted by tlg View Post
    Ha! I got them so cheap, I'd have to do that at a loss. I'm too friggin cheap for that.
    If that's the case and it were me, I would just give them away. Life is too short to ride tires just to use them up.
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



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