tubular tire size
07-23-09, 10:20 AM
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tubular tire size
May sound like a silly question, but I picked up a new bike yesterday with tubular rims. It's an 89 (last readable date on 'champion' stickers) or later Alan and the tires on it are marked "continental bts-41 universal 27x1". The rims just say 'nisi-toro' with a decal that says cierce nisi something (forgot the rest) but no visible size markings.
I was ready to order a couple spare tires, but then I ran into a few comments that stated some continentals were marked as 27's but were actually 700's. What is the best way to tell if these are 700 or 27?
I did mount a 700 clincher rim/tire, which showed the brakes were well positioned for a 700, But don't know if that's because of different tubular/clincher rim profiles or because they are the same size.
It's my first experience with tubulars in over 25 years and, so any input would be appreciated.
Ken.
I was ready to order a couple spare tires, but then I ran into a few comments that stated some continentals were marked as 27's but were actually 700's. What is the best way to tell if these are 700 or 27?
I did mount a 700 clincher rim/tire, which showed the brakes were well positioned for a 700, But don't know if that's because of different tubular/clincher rim profiles or because they are the same size.
It's my first experience with tubulars in over 25 years and, so any input would be appreciated.
Ken.
07-23-09, 10:35 AM
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Tubulars are always 700c, regardless of how they are labelled, whereas clinchers are available in both 27" and 700c. Some tubulars are labelled as 27 and I've even seen some labelled as 28, which is very confusing. Also, tubulars labelled as 26 are actually 650 size. A 27 tire/rim is approximately 3/8 inches larger diameter than a 700.
07-23-09, 12:20 PM
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Thanks, that's very good to know. I was starting to think I had stuck myself with another hard to find tire size!
I was aware of the rim size difference, but wasn't sure if the tubular not having the bead extensions would make a 27 fit the brakes like a 700.
Thanks again, will make finding the right tire a bit easier I think.
Ken
I was aware of the rim size difference, but wasn't sure if the tubular not having the bead extensions would make a 27 fit the brakes like a 700.
Thanks again, will make finding the right tire a bit easier I think.
Ken
07-23-09, 01:36 PM
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Correct. A 630mm bead seat diameter (BSD) corresponds to a 27" clincher (wired-on) rim. A 622mm BSD corresponds to a 700C clincher rim. Tubular tires do not have beads, so there is no BSD, however, the braking surface on a 700C tubular rim will be in the same radial location as a 700C clincher rim. There is also a 635mm BSD, which corresponds to a 28" clincher rim.
07-23-09, 01:46 PM
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And a standard tubular tire will fit on a 700c rim perfectly for stretching/quality-checking purposes.
