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PostPosted: Fri Dec 23, 2016 7:55 pm 
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I couldn't believe air does add weight to the bike, so tested it out myself, and :shock: Bike with both real 25mm tyres at around 90psi vs complete flat tyres made a whopping difference of 20gr! Not that you could win something in real usage, but it's a trick if you are just a few gr above 6kg and really want a scale pic at sub 6kg f.ex :mrgreen:

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Posted: Fri Dec 23, 2016 7:55 pm 


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PostPosted: Fri Dec 23, 2016 9:00 pm 
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Joined: Tue Aug 12, 2014 3:50 pm
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Location: FIN
pump with Helium ;)

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PostPosted: Fri Dec 23, 2016 9:35 pm 
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The "weight" of air is highly variable.


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PostPosted: Sat Dec 24, 2016 3:06 am 
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Joined: Thu Feb 12, 2015 9:40 am
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Location: Pom living in Australia
I put new tyres on the other day and did the same out of curiosity, air added 10gr.

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PostPosted: Sat Dec 24, 2016 3:11 am 
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Location: bottom edge of Australia
Low tyre pressures = WW trick! :P


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PostPosted: Sat Dec 24, 2016 2:56 pm 
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Joined: Tue Nov 15, 2016 8:13 am
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Also to note is if you are at altitude and pump your tyres up to the same pressure as at sea level. The bike will "weigh" more at sea level than at altitude.

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PostPosted: Sat Dec 24, 2016 9:09 pm 
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Joined: Fri Sep 25, 2015 5:13 pm
Posts: 250
This is true WW :D


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PostPosted: Sun Dec 25, 2016 5:06 pm 
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Joined: Tue Jan 20, 2015 3:43 pm
Posts: 116
So if you aren't too fat, you can run lower psi, more weight savings

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PostPosted: Thu Dec 29, 2016 6:01 pm 
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Joined: Thu Dec 29, 2016 5:16 pm
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Location: Bentonville, Arkansas USA
It isn't so much a change in weight as it is a change in density... You are adding more air molecules into the relatively same volume of space.

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PostPosted: Fri Dec 30, 2016 7:26 am 
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TeslaOsiris wrote:
It isn't so much a change in weight as it is a change in density... You are adding more air molecules into the relatively same volume of space.


That is a good technical correction and reminder of the physics at work.


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PostPosted: Sat Jan 07, 2017 4:36 pm 
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TheKaiser wrote:
TeslaOsiris wrote:
It isn't so much a change in weight as it is a change in density... You are adding more air molecules into the relatively same volume of space.


That is a good technical correction and reminder of the physics at work.

No, it's tautologous gibberish. By definition a change in density for the same volume is a change in weight, assuming constant gravity.


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PostPosted: Sat Jan 07, 2017 5:21 pm 
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Location: Bentonville, Arkansas USA
964Cup wrote:
TheKaiser wrote:
TeslaOsiris wrote:
It isn't so much a change in weight as it is a change in density... You are adding more air molecules into the relatively same volume of space.


That is a good technical correction and reminder of the physics at work.

No, it's tautologous gibberish. By definition a change in density for the same volume is a change in weight, assuming constant gravity.

I think the word you are looking for is "mass", not weight ;) Density is a ratio of mass:volume... Weight is a measurement of gravitational attraction. But what does my tautologous gibberish know? (That's not even a tautology is, FYI)

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PostPosted: Sun Jan 08, 2017 2:10 pm 
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TeslaOsiris wrote:
I think the word you are looking for is "mass", not weight ;) Density is a ratio of mass:volume... Weight is a measurement of gravitational attraction. But what does my tautologous gibberish know?

Apparently your tautological gibberish doesn't know that we all live on the surface of the earth, therefore when you increase the mass of a bike you increase the weight by exactly the same degree, always. The word 'weight' is equally as valid as the word mass. If there's anything worse than being that pedantic it's being that pedantic and wrong :roll:

This applies equally to your original point. Air has weight. Adding more air to tyres adds more weight. This statement is no less valid because the density of the air in the tyres has also increased. It's not a situation where one or the other is true. They are both equally true at the same time.


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PostPosted: Fri Jan 20, 2017 3:29 pm 
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TeslaOsiris wrote:
964Cup wrote:
TheKaiser wrote:
TeslaOsiris wrote:
It isn't so much a change in weight as it is a change in density... You are adding more air molecules into the relatively same volume of space.


That is a good technical correction and reminder of the physics at work.

No, it's tautologous gibberish. By definition a change in density for the same volume is a change in weight, assuming constant gravity.

I think the word you are looking for is "mass", not weight ;) Density is a ratio of mass:volume... Weight is a measurement of gravitational attraction. But what does my tautologous gibberish know? (That's not even a tautology is, FYI)


I wonder why I said "assuming constant gravity" in my original post? And it is a tautology, because you are saying the same thing twice. Adding more molecules into the relatively same volume of space [sic] is indeed a change in density which is precisely as much a change in weight. They are (for a constant volume in constant gravity) exactly the same thing. (Even more amusingly, and tautologically, our common measures of mass are also measures of weight at Earth-normal gravity.)

[/pedant mode]


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Posted: Fri Jan 20, 2017 3:29 pm 


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