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Old 09-06-07, 08:30 AM   #1
Tourister
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Tube compatiblity

I just discovered somithing ... I have an old "Bobby" bike with the 28 inch wheels on it.. In the process of putting a computer on it I checked the rollout on the wheel and it came to 88 inches,, This is with the standard 28x1 1/2 inch tire on it... What surprised me is that my 06 Cypress DX with Nimbus 700c x 38's also have a 88 inch rollout... Does this mean I can use the 700c tubes in my 28 inch wheels ?... I haven't been able to find Thornproof tubes in the 28 inch size but they are abailable in the 700c size.. Visually the width doesn't seem that far apart either.. Makes me wonder if a 700c tire will fit the 28 inch rim :-)
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Old 09-06-07, 08:55 AM   #2
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I thought "28 inch" is a term sometimes used for 700c, in some parts of the world. I could be mistaken, though. The key to the tires being interchangeable, besides staying within broad width limitations, is the bead seat diameter of the tires/rims. 700c is 622mm bead seat diameter. Inner tubes are another matter. For example, 27 inch tires (630mm bead seat diameter) and 700c tires, again staying within reasonable width limitations, can use the same sized inner tubes-
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Old 09-06-07, 09:36 AM   #3
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Beats me... The Bobby bike is over 30 years old.. Hope your right, that opens up a lot more options for tire/tubes for the bike... I could put Armidillos on my Bobby bike too then... That would be great..
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Old 09-06-07, 09:41 AM   #4
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I would look very closely at the sidewalls of the tires on the Bobby bike, see if you see the number 622 anywhere. Something like 622-38, which would be the bead seat diameter and the width. If the rims aren't 622mm bead seat diameter, they won't work with 700c tires-
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Old 09-06-07, 09:44 AM   #5
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I'm now thinking the tires on your Bobby aren't 622, because there's a size, 28 x 1 1/2, that's a separate size altogether. Seems more likely yours are 635mm BSD. Some "28 inch" tires do indeed have a 622 BSD, though. Check this out, scroll down to the "fractional sizes" chart:

http://www.sheldonbrown.com/tire-sizing.html

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Old 09-06-07, 12:07 PM   #6
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Thanks for the llink... I think your right, mine must be the 635's... Sure looks like mass confusion... Too bad, it would have done well with a got flatproof set of tires :-)
I would think the ThornProof tubes would work though ?... That and some liners qhould help quite a bit...
Thanks

Last edited by Tourister; 09-06-07 at 12:28 PM.
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Old 09-06-07, 12:20 PM   #7
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Quote:
Originally Posted by Tourister View Post
I just discovered somithing ... I have an old "Bobby" bike with the 28 inch wheels on it.. In the process of putting a computer on it I checked the rollout on the wheel and it came to 88 inches,, This is with the standard 28x1 1/2 inch tire on it... What surprised me is that my 06 Cypress DX with Nimbus 700c x 38's also have a 88 inch rollout... Does this mean I can use the 700c tubes in my 28 inch wheels ?... I haven't been able to find Thornproof tubes in the 28 inch size but they are abailable in the 700c size.. Visually the width doesn't seem that far apart either.. Makes me wonder if a 700c tire will fit the 28 inch rim :-)
Thanks
Tubes are flexible, so there's a lot of wiggle room. You can use pretty much any tube of "roughly" the right size. In a pinch, you can use a wide 700C tube in a 26" tire, or vice versa... though you have to be careful not to tangle the tube up when putting it in, which can be quite a pain.

And, since 27" and 700C tires only differ by 8mm in diameter, tubes for the two sizes are completely interchangeable, even labeled as such on the boxes.

Tires are quite different, however. The bead seat diameter must match exactly between the tire and wheel in order to fit. See Sheldon Brown's page for some ideas about what your 28in wheels/tires might be: http://sheldonbrown.com/tire-sizing.html ... it sounds like they may actually be 622mm, though no guarantees.
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Old 09-06-07, 12:25 PM   #8
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Uh.....
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Old 09-06-07, 01:05 PM   #9
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If you can find "pure" 27x1-1/4" tubes, you wouldn't have to stretch them as far as 700C tubes. Only 5MM VS 13MM diameter.
Don't forget PI! Stretch is around the whole circumference, so a 13MM diameter difference is 41MM circumference difference.
Harris lists 635MM tubes for $6.
http://sheldonbrown.com/harris/tires/635.html
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