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Question: How does one measure their frame in order to know which size rims will fit?

Context: Flatmate left a few months ago, forgot (perhaps intentionally) a Traitor Cutlass frame. When asked, he said keep it.

I read Wheelpro's ebook on wheelbuilding. Tons of great information. I'm excited to get started. One subject not covered, and something I've been having a difficult time finding resources on - is how to know whether a rim will fit?

I understand the rim to frame isn't the only equation - tire size, brakes, fender, ect. all need to be considered too. Are there any calculators or rules of thumb which I should be aware of before blindly buying a 700c and hoping it all works out?

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  • Surely you know someone with a 700 you can slip in and test. – paparazzo Mar 20 '17 at 13:57
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    The linked web page says frame will accept up to 700x35c tires. Isn't this what you are looking for? – Klaster_1 Mar 20 '17 at 14:29
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    If the frame is for rim brakes then that decides everything. – Daniel R Hicks Mar 20 '17 at 17:04
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    @Paparazzi - ??? That bike has rim brakes. One needs to examine the brakes, however, to know the precise distance from brake bolt to rims. Or one could just look at the specs and see that it's a 700c wheel. – Daniel R Hicks Mar 21 '17 at 2:02
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    @Paparazzi - A 700c wheel has a 622mm bead seat diameter, which would mean a 311mm radius. But note that, according to Sheldon, "The rim's diameter will generally be 5-10 mm larger than the bead-seat diameter, depending on how high the rim flanges stick up above the bottom of the rim channel." Roughly speaking, the brake pads for rim brakes should be positioned at about the bead seat, so for a 700c they would be 311mm from the center of the axle dropout slot. – Daniel R Hicks Mar 21 '17 at 2:36
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A 700c wheel has a 622mm bead seat diameter, which would mean a 311mm radius.

But note that, according to Sheldon, "The rim's diameter will generally be 5-10 mm larger than the bead-seat diameter, depending on how high the rim flanges stick up above the bottom of the rim channel." So when Paparazzi measured a 12.5 inch (317mm) radius on a 700c wheel he was seeing 6mm larger than the bead seat radius, which is in the expected range.

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Roughly speaking, the brake pads for rim brakes should be positioned at about the bead seat (so as to fall on the flat of the rim), so for a 700c they would be roughly 311mm from the center of the axle dropout slot

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