Inner tube sizing

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mark a.
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Inner tube sizing

Postby mark a. » 21 Jan 2015, 2:23pm

I'm sure this has been asked loads before, but search is swamped with irrelevant results.

I have 32mm tyres (700c). For new Continental inner tubes, for example, I can buy 25-32mm, or 32-47mm.

I went for the bigger ones, but I wonder if anyone can notice any difference. Would it just be the bigger ones are heavier and perhaps more puncture resistant (since they won't be stretched as much)?

beardy
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Re: Inner tube sizing

Postby beardy » 21 Jan 2015, 2:48pm

I doubt that it will be any more puncture resistant but it should keep pressure longer as the air takes longer to permeate through the thicker rubber.

There is also the Continental Cross 28 inner tube which is a rather ideal 25-35mm size.

ardeidae
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Re: Inner tube sizing

Postby ardeidae » 21 Jan 2015, 2:53pm

Our venerable lbs man told me, and I believe him, that tubes have better functional strength under actual tension rather than just being blown up to size. Hence I use 18/23 tubes in my 700x28 tyres.

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Vantage
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Re: Inner tube sizing

Postby Vantage » 21 Jan 2015, 3:01pm

I doubt even the most weight conscious of riders would notice any difference in a few grams, but the smaller tubes would make for easier fitting since they are less bulky when squeezing into the tyre.
As for puncture resistance, you might be more likely to spot a difference between manufacturers than sizes. I'm with beardy on the air leaking thing though. Stretch the tube more and you stretch the tubes pores more.
Bill


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Redvee
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Re: Inner tube sizing

Postby Redvee » 21 Jan 2015, 3:19pm

Vantage wrote:Stretch the tube more and you stretch the tubes pores more.


Not the pores but the molecules that make up the tube.

Rhodrich
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Re: Inner tube sizing

Postby Rhodrich » 21 Jan 2015, 3:29pm

One thing worth noting is that a puncture repair on a tube that is too small is likely to be unreliable, in my experience. The patch will stick perfectly, but once the tube is inflated over its design rating, the patch has a tendency to fail.

ardeidae
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Re: Inner tube sizing

Postby ardeidae » 21 Jan 2015, 4:00pm

Rhodrich wrote:patch has a tendency to fail

That would be down to faulty patching technique. My patches bond to the tube.

Rhodrich
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Re: Inner tube sizing

Postby Rhodrich » 21 Jan 2015, 4:34pm

ardeidae wrote:
Rhodrich wrote:patch has a tendency to fail

That would be down to faulty patching technique. My patches bond to the tube.


My patches never fail when they're used in the correct sized tyres. There is a lot of strain on a patch on a tube designed for a 23mm tyre, when it's used in a 28 or a 32 however. Simply put, patches are not as stretchy as tubes.

sreten
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Re: Inner tube sizing

Postby sreten » 22 Jan 2015, 1:42am

Hi,

Of the marginal choice, the bigger tubes wll keep air better.

FWIW given the claim its suitable for 47mm for 32 mm I would
have gone for the smaller of the two choices, given a choice.

rgds, sreten.

mark a.
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Re: Inner tube sizing

Postby mark a. » 22 Jan 2015, 2:19pm

OK, some people like the smaller, some like the bigger.

I happened to go with the bigger mainly because my wife's tyres are 38mm so I needed tubes that'll fit both. Glad I'm not obviously missing out on something crucial by not having the smaller tube in my bike.

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andrew_s
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Re: Inner tube sizing

Postby andrew_s » 22 Jan 2015, 2:34pm

mark a. wrote:Would it just be the bigger ones are heavier and perhaps more puncture resistant (since they won't be stretched as much)?

They probably won't puncture any less often, but many of the punctures you do get will be "slow" punctures that you find when your tyre is flat or soft the next morning, or that allow you to get home by pumping up the tyre every few miles rather than changing the tube.
I had a 1" long thorn through my tyre for a couple of months once - I had to pump a couple of times a week, and found the thorn when I got fed up with doing so.
I generally go for the larger option.