700x20c-25 vs. 700x20c race 28 vs. the theory of everything



Fatty Lumpkin

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Dec 5, 2016
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Here I am with another noob moment when I ask for help. This time, it’s about inner tubes.

Over the past year, when I need a new inner tube for either of my bikes, I got them directly at the bike store. They looked at the tire and picked it for me. Then I went and ordered some online but they don’t look exactly the same width. Close, but not exactly. Are the new tubes I got online the wrong size? What’s the difference here?

What I got at the bike store (which fits):

700x20c-25 (That’s what it says on the side of the physical inner-tube)

What I ordered online:

700x20c-25c Race 28
https://www.amazon.com/gp/product/B01M6AUWM8/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

Race 28? They seem slightly narrower. Will they work or should I return them?

Thank you in advance for any help you can offer.
 

dhk2

Well-Known Member
Aug 8, 2006
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You have the right size (for 700x20-25mm tires). Race 28 is just Conti's name for the 700C tubes...28" in Old Money.
 

CAMPYBOB

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Sep 12, 2005
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What dhk2 said. 28 is Continental's nomenclature for 700c diameter tires. Your online purchased inner tubes are designed to fit tires from 20 MM in width to 25 MM in width...give or take a MM or two. You could safely cram them into a 19 MM tire or let them stretch out just a bit into a 26-27 MM tire.
 

Fatty Lumpkin

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Dec 5, 2016
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Thanks for the input, guys. I feel better and will keep the new tubes! Its just weird to me that they look so different.
 

dabac

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Sep 16, 2003
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[QUOTE="Fatty Lumpkin, post: 3826586, member: 274028] ... Are the new tubes I got online the wrong size? What’s the difference here?

What I got at the bike store (which fits):

700x20c-25 (That’s what it says on the side of the physical inner-tube)

What I ordered online:

700x20c-25c Race 28
https://www.amazon.com/gp/product/B01M6AUWM8/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

Race 28? They seem slightly narrower. Will they work or should I return them?[/QUOTE]

Tubes have virtually no structural strength to themselves. They're only there to provide an air-tight layer. They'll stretch to fill the tire. Or possibly burst in the process, if the size is REALLY wrong. But that's VERY rare.
Since they are so stretchy (try inflating one outside the tire) each actual size made will fit several tire sizes.
So it's real common that different make tubes for the same size tire will have different sizes uninflated.

Easiest way to make a light tube ( maybe a "race" tube) is to re-label a thinner tube as meant for a wider tire.
 

Fatty Lumpkin

Member
Dec 5, 2016
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Thanks, dabac. I've only changed 2 tires and did explode one of them. My wife had to come get me. My boys (6 & 10) were in the car and harassed me endlessly: "Dad, are you KOM of flat tires?" And, "Dad, you fail at cycling!" Actual statements. They thought it was so funny. Anyway, I had only 1 tube that day so once it popped I had to call for help. That's what lead to purchasing a few extra for both bikes. I do appreciate the info. I'm still learning.
 
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dabac

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Sep 16, 2003
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I've only changed 2 tires and did explode one of them.
Blowing tires is kinda rare, but does happen. Blowing tubes are more common. Usually b/c a fold of tube has gotten trapped underneath the bead. I usually install tubes while inflated just enough to keep their shape to help avoid that.
 

Mr. Beanz

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Aug 18, 2015
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Thanks, dabac. I've only changed 2 tires and did explode one of them. My wife had to come get me. My boys (6 & 10) were in the car and harassed me endlessly: "Dad, are you KOM of flat tires?" And, "Dad, you fail at cycling!" Actual statements. They thought it was so funny. Anyway, I had only 1 tube that day so once it popped I had to call for help. That's what lead to purchasing a few extra for both bikes. I do appreciate the info. I'm still learning.

As mentioned, I slightly inflate the tube to keep it's shape. I blow it up with my mouth before even starting to install it. I can blow it up with my mouth to the perfect amount this way, not being able to blow it up anymore. It works! :D

After inserting the tube, I inflate the tire/tube to maybe 15-2- psi. Then I make actually pinch the tire together with my fingers looking inside the rim wall and tire bead to make sure the tube is not pinched. Also doing this allows me to verify that the tire bead is seated properly.

If all is well, then I continue inflating to desired psi. Then I spin the wheel around and look at the line along the bead of the tire to make sure it is somewhat consistent and mounted evenly on the rim. With some practice, this only takes 30 seconds or so. Maybe a minute or two pinching as mentioned above.

An extra couple of minutes to do this stuff but it beats having your kids laugh at you! :D
 

Froze

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Jul 13, 2004
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As mentioned, I slightly inflate the tube to keep it's shape. I blow it up with my mouth before even starting to install it. I can blow it up with my mouth to the perfect amount this way, not being able to blow it up anymore. It works! :D

After inserting the tube, I inflate the tire/tube to maybe 15-2- psi. Then I make actually pinch the tire together with my fingers looking inside the rim wall and tire bead to make sure the tube is not pinched. Also doing this allows me to verify that the tire bead is seated properly.

If all is well, then I continue inflating to desired psi. Then I spin the wheel around and look at the line along the bead of the tire to make sure it is somewhat consistent and mounted evenly on the rim. With some practice, this only takes 30 seconds or so. Maybe a minute or two pinching as mentioned above.

An extra couple of minutes to do this stuff but it beats having your kids laugh at you! :D

this is the best way to mount a tire, nice explanation.

also using talcum powder, or baby powder on the tube will allow the tube to settle into it's position faster and reduce the chance of a pinch flat, not only that but it's been discovered that a liberal amount of that powder on the tube reduces rolling friction to close to the level of latex tubes...anyway that's what I read a month or so ago, not sure how accurate the info was.
 
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Mr. Beanz

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Aug 18, 2015
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this is the best way to mount a tire, nice explanation.

also using talcum powder, or baby powder on the tube will allow the tube to settle into it's position faster and reduce the chance of a pinch flat, not only that but it's been discovered that a liberal amount of that powder on the tube reduces rolling friction to close to the level of latex tubes...anyway that's what I read a month or so ago, not sure how accurate the info was.


OH yeah, powder. I failed to mention that I carry my 2 extra tubes in my seat pack, double baggy and some powder inside the baggies to keep them dry etc. So they usually have powder on them.

I didn't know about the resistance thing. Not sure how much that would help me anyway! :D