Inner Tubes - Are the sizes stamped on them?

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RideToWorky
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Joined: 23 Oct 2015, 1:14pm

Inner Tubes - Are the sizes stamped on them?

Post by RideToWorky »

Hi All,

Inner Tubes - Are the sizes stamped on them?
would they rub off with riding the bikes?

If no markings, would 700c (25-32), and (20-28) be easy to recognize, if the've been pumped up in 25mm tyres?


Reason why asking:
I'm changing from 25mm to 28mm tyres.

Be good to know what inner tubes are on the bike, when I take off the 25mm tyres.
Can then decide then, if I'll keep the same inner tubes on the bike, or replace with the (25-32) Inner tubes I've also ordered.
They have only been on the bike for say 750 miles so far


Hope you can advise


Regards
Martin
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Paulatic
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Re: Inner Tubes - Are the sizes stamped on them?

Post by Paulatic »

There's usually something printed or embossed on them. Lay them flat beside your new ones and you'll see if there is much difference in size.
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drossall
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Re: Inner Tubes - Are the sizes stamped on them?

Post by drossall »

Tubes that fit 25mm are probably going to fit 28mm anyway. There's a fair bit of latitude in tube sizing.
Roadster
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Re: Inner Tubes - Are the sizes stamped on them?

Post by Roadster »

Can't speak to all brands, but both Michelin and Schwalbe usually have the sizes moulded onto them and there's no chance of the information rubbing off. Even if they don't, you can simply compare them side-by-side with new ones of known size.

Tyres themselves are often different from their nominal sizes, some being larger and some smaller. Because of this variation, I prefer to incorporate a safety margin by using a tube-size which falls in the middle or upper end of the recommended range, rather than one which falls right at the lower end.

At their modest cost, tubes are simply not worth agonizing over: if in any doubt, just use the new ones you've ordered and donate the old ones to your nearest bike recycling centre.
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meic
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Re: Inner Tubes - Are the sizes stamped on them?

Post by meic »

Let me propose a rule of thumb (or Meic's second law of cycling).
That if you measure the width of an innertube laid flat on a surface, it will comfortably fit a tyre which is nominally from 10% less to 20% more than that width.

So my prediction is that when your new 25-32mm tubes arrive, they will be 27/28mm wide.
Your 20-28mm tubes I would expect to be 23mm wide when laid flat.
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Gattonero
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Re: Inner Tubes - Are the sizes stamped on them?

Post by Gattonero »

There's no real need for markings, just a bit of observation.
Lightly inflate the inner tube with the mouth, so that it just barely takes shape, put it over a tyre and you'll see if the diameter is correct.

As far as width, keep in mind that Butyl does stretch a lot, so if the barely inflated tube is bout 25mm you could use it up to 30-32mm.
Just make sure does not stretch too much, i.e. a 35mm would get the tube too stretched, although could be used in emergency.

On the other hand, a 30mm inner tube won't do well in a 23mm tyre, will crease and could get damaged, also will be difficult to fit.

Of course, this applies for standard gauge of inner tubes, lightweight ones have a thin gauge of rubber so is better to use them for the right width of tyre.
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RideToWorky
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Joined: 23 Oct 2015, 1:14pm

Re: Inner Tubes - Are the sizes stamped on them?

Post by RideToWorky »

meic wrote:Let me propose a rule of thumb (or Meic's second law of cycling).
That if you measure the width of an innertube laid flat on a surface, it will comfortably fit a tyre which is nominally from 10% less to 20% more than that width.

So my prediction is that when your new 25-32mm tubes arrive, they will be 27/28mm wide.
Your 20-28mm tubes I would expect to be 23mm wide when laid flat.



You were bang on! 8)
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