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  1. #1
    Indefatigable RideCO's Avatar
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    confused newbie 700c tire size question

    I have 700 X 25C (25 - 622) tires on my road bike and I am confused on whether some tires and tubes a friend has will fit. He has a bunch of unused tires, still in the packages, varying in size but are all labeled in inches. If I understand Sheldon Brown correctly I can use 28 x 1 5/8 x 1 1/4 is that right? I am confused because the tubes I get from LBS are say (700 x 20/28C, 27 x 3/4" - 1 1/8") so the 27 on the tubes throws me off. Also does the same conversion apply to tubes, er... what size tubes can I use? tubes are only labeled in inches.

    These tires are cheap and I don't want to put a lot of money into this bike so I am trying to find out if I can make use of them. Every $ I save is a $ towards my new bike.
    Buy the ticket, take the ride.

  2. #2
    Packfodding 3 caloso's Avatar
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    I'm pretty sure those will fit. To add to the confusion, some 700c tires/tubes are labeled "28 in." The biggest concern is whether it's the correct valve for you rim.
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  3. #3
    Senior Member
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    Nothing but a 700 x XXmm tire will fit on your 622 ERD rims. 27" tires will be too big. Tubes, on the other hand, are sometimes labelled for 27" tires as well as 700 x XXmm tires. If the valve is the same and the tube fits easily inside of your tire (not too large of a diameter), there's no problem with using them.

  4. #4
    Packfodding 3 caloso's Avatar
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    I'm sorry. I misread the question. The discussion about tubes threw me. JoeJack is absolutely right.
    Cyclists of the world, unite! You have nothing to lube but your chains!

  5. #5
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    I'm confused - are there tires and tubes? Tubes stretch and can easily work for both 700c and 27", and anything 28"...
    Tires are not interchangable between 700 an d 27", though - the 27" tires are slightly too big for 700c rims and will not mount correctly.

    28" tires are generally the same diameter as 700c, but most of the tires I have seen in the 28" sizes tend to be wider and may not fit inside the frame and fork of a bike that came stock with 700 X 25 tires. Also, if the rims on the bike are quite narrow then mounting high pressure wide tires can be bad, or so I have been told.

    Sheldon brown says the following tires will fit... (Sheldon knew his stuff better than anyone currently on these forums)
    622 mm: 700 C, 28 x (two fractions), 29 inch
    (28 x 1 1/2 F.13 Canada)

  6. #6
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    Despite all of the confusing nomenclature, the really definitive way to know if a given tire will fit your rim is to look for the ETRTO/ISO size embossed on the sidewall. If it says 622-XX it will fit a 700c rim. If it says anything else (like 630-XX) it will not fit.

    Tubes are much less limited and 700c and 27" tubes are interchangable as long as the width is at all close to the tire width.

  7. #7
    Senior Member chunt's Avatar
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    So, regarding tube sizes - will a 700c x 20-23 tube work in a 700c x 25 tire?

  8. #8
    Senior Member BCRider's Avatar
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    Quote Originally Posted by chunt View Post
    So, regarding tube sizes - will a 700c x 20-23 tube work in a 700c x 25 tire?
    Yes, tubes stretch just fine over that much range. In a pinch you can even use a 23 tube in a 28 or 32 mm tire but that's pushing it and I wouldn't suggest you leave it that way for long.

    There is one little issue with using an undersized tube though. Because it has to stretch to shape to fill the tire instead of being big enough to fit without swelling when you get a puncture it'll tend to deflate quicker since the puncture hole pulls open. We aren't talking much of a difference though. Like if a little wire makes a leak that runs down in 5 minutes in a normal fitted tube the undersized tube stretched into place would take 1 or 2 minutes to leak down the same amount.

    But if they are free or near too it I'd say let 'em stretch and let's go riding!
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  9. #9
    Senior Member DannoXYZ's Avatar
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    The other issue with stretching small tubes to large sizes is the seams can split apart easier. Seems to happen with older tubes that's been in use for a while.

  10. #10
    Senior Member Bill Kapaun's Avatar
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    A tube that is overly stretched will probably need to have the air "topped off" more frequently and be slightly more prone to flats from thorns and similar objects.

  11. #11
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    In your case it is possible to find a larger tire that might fit the rim but won't fit inside the frame or fork. It will be best for you to stay with 700 x 25c or 700 x 23c tires.

    Al

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