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How many 16 gram CO2 cylinders for a 17" tire?

  
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M. MacDonald

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Since: Feb 08, 2006
Posts: 23



(Msg. 1) Posted: Mon Sep 17, 2007 1:26 pm
Post subject: How many 16 gram CO2 cylinders for a 17" tire?
Archived from groups: rec>motorcycles>tech (more info?)
Regarding those CO2 tire inflator kits, anyone know how many cylinders it
takes to get a rear 180x70x17 tire back up to 40 psi?

Dealer says a lot, maybe 7-8 cylinders.

Anyone need to use one?

Tia.

Mack

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Rick Cortese

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Since: Feb 27, 2004
Posts: 189



(Msg. 2) Posted: Mon Sep 17, 2007 10:05 pm
Post subject: Re: How many 16 gram CO2 cylinders for a 17" tire? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
M. MacDonald wrote:
> Regarding those CO2 tire inflator kits, anyone know how many cylinders it
> takes to get a rear 180x70x17 tire back up to 40 psi?
>
> Dealer says a lot, maybe 7-8 cylinders.
>
> Anyone need to use one?
>
> Tia.
>
> Mack

My excuse is this is a technology group. Been a while so double check
for mistakes.

CO2 => MW of 44g/mole.

1 mole of gas at STP is 22.4 liters => 16g will make 8.1 liters. Imagine
something like an empty garbage bag that wouldn't increase the pressure
the gas was under when you inflated it to hold the gas. STP is standard
temp and 1 atm of pressure. If you don't have a feel for liters, ~2 gals
of dead air.

Gases volume are inversely proportional to pressure. Of course it
depends on how big of a tire you are inflating but take 4 liters as an
model. The first cylinder will inflate it to 15 lbs: 8 liters at 1
atmosphere squeezed into a 4 liter space => two atmospheres or ~30 PSI
or 15 lbs greater/differential then outside.

From there it should go up 30 PSI for every extra cylinder. That is,
when you have 2 => 16 liters in 4 liters of space or 4 atms or 60 psi or
45 psi greater then sea level pressure.

As some people have pointed out, the volumes for some tires is much
greater then 4 liters and it would require proportionately more
cylinders to get to a usable pressure. I can't see someone on a cruiser
finding them useful.

On the other hand, those little Mickey Mouse pumps like Mark talks about
are useful to a point. I mean their gages may go to 200 PSI but you are
lucky to get 20 PSI out of the one I own. The one good thing about the
CO2 cylinders is they will go to something like 180 PSI. If you can
afford the room/weight, you may want to carry the pump for getting the
tire up to a marginal inflation level and the cylinders to a safe
operating level.

Rick

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Rob Kleinschmidt

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Since: Jun 07, 2007
Posts: 71



(Msg. 3) Posted: Mon Sep 17, 2007 11:59 pm
Post subject: Re: How many 16 gram CO2 cylinders for a 17" tire? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
On Sep 17, 12:26 pm, "M. MacDonald" <mmacdon... DeleteThis @bc.cc.ca.us> wrote:
> Regarding those CO2 tire inflator kits, anyone know how many cylinders it
> takes to get a rear 180x70x17 tire back up to 40 psi?
>
> Dealer says a lot, maybe 7-8 cylinders.
>
> Anyone need to use one?

I don't think you need 7-8 cylinders, but a pump
would be less bulky if you did.

I normally use a $10 Walmart tire inflator with
the plastic housing and fan removed. At a rally
last weekend, I saw the same $10 Walmart pump
reworked a little more elegantly than I'd bothered
with selling for ~ $45.

Wire an ordinary lighter socket into the electrics
to provide an outlet to plug the pump into. Also
very useful for quickly inflating your air mattress
at night when you pitch camp.
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The Older Gentleman

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Since: Jan 05, 2007
Posts: 1132



(Msg. 4) Posted: Tue Sep 18, 2007 2:45 am
Post subject: Re: How many 16 gram CO2 cylinders for a 17" tire? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
M. MacDonald <mmacdonald.TakeThisOut@bc.cc.ca.us> wrote:

> Regarding those CO2 tire inflator kits, anyone know how many cylinders it
> takes to get a rear 180x70x17 tire back up to 40 psi?
>
> Dealer says a lot, maybe 7-8 cylinders.
>
> Anyone need to use one?
>
Not yet. I think BMW packs two or maybe three in their puncture kits
(I'd have to check), and so I'd assumer they know the reality, and pack
that many.


--
BMW K1100LT 750SS CB400F CD250 CB125 SL125
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
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The Older Gentleman

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Since: Jan 05, 2007
Posts: 1132



(Msg. 5) Posted: Tue Sep 18, 2007 2:45 am
Post subject: Re: How many 16 gram CO2 cylinders for a 17" tire? [Login to view extended thread Info.]
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Mark Olson <olsonm RemoveThis @tiny.net> wrote:

> So, I have a mini 12V air compressor in my toolkit, it does the trick,
> it was less than $10 and it takes up no more space or weight than a
> handful of CO2 cartridges.

Genius idea.

I'm off to the shops to get one today.


--
BMW K1100LT 750SS CB400F CD250 CB125 SL125
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....
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Ken Abrams

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Since: Aug 01, 2006
Posts: 107



(Msg. 6) Posted: Tue Sep 18, 2007 8:17 am
Post subject: Re: How many 16 gram CO2 cylinders for a 17" tire? [Login to view extended thread Info.]
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"Mark Olson" <olsonm.TakeThisOut@tiny.net> wrote

> Ken, have you ever used CO2 cartridges to inflate a motorcycle tire?
> If not, why is your guess any better than the dealer's guess?
>

It isn't any better......without qualification, that is
..
I hadn't considered seating the bead on a tubeless application.
My only experience was with a patched tube.

Sounds like those with experience in that arena much prefer a
mini-compressor but even with that, I can't help but wonder if getting the
bead seated might be more a matter of luck than skill, as I doubt that the
air flow would really help much.
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Mark Olson

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Since: Jul 18, 2003
Posts: 1532



(Msg. 7) Posted: Tue Sep 18, 2007 11:29 am
Post subject: Re: How many 16 gram CO2 cylinders for a 17" tire? [Login to view extended thread Info.]
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Ken Abrams wrote:

> I hadn't considered seating the bead on a tubeless application.
> My only experience was with a patched tube.
>
> Sounds like those with experience in that arena much prefer a
> mini-compressor but even with that, I can't help but wonder if getting the
> bead seated might be more a matter of luck than skill, as I doubt that the
> air flow would really help much.

The mini compressors are useless for seating a tubeless tire bead. There
just isn't enough airflow. It's possible that a large CO2 cartridge might
have an advantage there, but since I've never used one I won't speculate.
To be clear, the one guy who did talk about seating a bead with a CO2
cartridge was talking about a tubed tire, where a mini compressor would
work just as well. To seat a tubeless tire once the tire's come off, you
need to either wrap the tire's circumference with a band or rope and/or
have a pretty decent amount of airflow to overcome the leakage. I managed
it one time with the wheel in place on my GL1200 after a flat, but it
was a bastard of a job with three guys working on it simultaneously, and
we had a proper air compressor with a good sized tank.

--
'01 SV650SK1 '99 EX250-F13 '98 ZG1000-A13
OMF #7
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Ron Gibson

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Since: Sep 15, 2007
Posts: 31



(Msg. 8) Posted: Tue Sep 18, 2007 2:48 pm
Post subject: Re: How many 16 gram CO2 cylinders for a 17" tire? [Login to view extended thread Info.]
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On Mon, 17 Sep 2007 23:59:35 -0700, Rob Kleinschmidt wrote:

>> Dealer says a lot, maybe 7-8 cylinders.

> I don't think you need 7-8 cylinders, but a pump would be less bulky if
> you did.

I use a regular Kmart bicycle pump for 110/90-18. Might take a bit of
time pumping one up that was completely flat but I can go from 30 to 40
PSI in about 3-4 minutes or about 8-10 pump strokes.

--
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Ron Gibson

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Since: Sep 15, 2007
Posts: 31



(Msg. 9) Posted: Tue Sep 18, 2007 3:15 pm
Post subject: Re: How many 16 gram CO2 cylinders for a 17" tire? [Login to view extended thread Info.]
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On Mon, 17 Sep 2007 22:05:17 -0700, Rick Cortese wrote:

> My excuse is this is a technology group. Been a while so double check
> for mistakes.

Use the Ideal Gas Law...PV=nRT

http://wiki.answers.com/Q/What_is_the_Ideal_Gas_Law

You'll have to do some dimensional conversions especially for the cans
and determine the volume of the tire. Maybe not though because some
values may cancel out. Might be able to use the form...

P(1)*V(1)/P(2)*V(2)=N(1)*T1(1)/N(2)*T(2)

The R cancels and off the top of my head so should the T's but unless I
start crunching numbers I can't be sure. My specialty is HVAC so I don't
use the Ideal Gas Law a lot anymore but it should work.

You could use the volume of a torus to approximate the volume of the
tire...

The specific formula is here...

http://en.wikipedia.org/wiki/Torus#Geometry

General info...

http://en.wikipedia.org/wiki/Torus

Again off the top of my head that approximation should get you within
90%+ of the true tire volume. If you're a math whiz kid you can refine
the volume further after making the first approximation. But I'd just
but one extra can to cover myself. It's too much work refining the volume
numbers further unless I'm getting paid Smile

--
Linux Help: http://rsgibson.com/linux.htm
Email - rsgibson DeleteThis @verizon.borg
Replace borg with net
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Rick Cortese

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Since: Feb 27, 2004
Posts: 189



(Msg. 10) Posted: Wed Sep 19, 2007 11:52 am
Post subject: Re: How many 16 gram CO2 cylinders for a 17" tire? [Login to view extended thread Info.]
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Ron Gibson wrote:

> On Mon, 17 Sep 2007 22:05:17 -0700, Rick Cortese wrote:
>
>
>>My excuse is this is a technology group. Been a while so double check
>>for mistakes.
>
>
> Use the Ideal Gas Law...PV=nRT

I did. The 22.4 liters/mole is the derived part from n and R so the only
thing left is atmospheric pressure and temperature which falls out most
places you can operate a motorcycle i.e. ~sea level and 20C.
<snip>
> You'll have to do some dimensional conversions especially for the cans
> and determine the volume of the tire. Maybe not though because some
> values may cancel out. Might be able to use the form...

Not in this particular case because the CO2 in the cylinder is probably
liquid/gas. The 16 grams is the only thing you can count on for
quantity. I should go to the handbook of chemistry and physics to make
sure about my 180 PSI at ~20C but feeling a bit lazy.

Rick
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Ron Gibson

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Since: Sep 15, 2007
Posts: 31



(Msg. 11) Posted: Thu Sep 20, 2007 12:10 am
Post subject: Re: How many 16 gram CO2 cylinders for a 17" tire? [Login to view extended thread Info.]
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On Wed, 19 Sep 2007 11:52:53 -0700, Rick Cortese wrote:

> Not in this particular case because the CO2 in the cylinder is probably
> liquid/gas. The 16 grams is the only thing you can count on for quantity.
> I should go to the handbook of chemistry and physics to make sure about my
> 180 PSI at ~20C but feeling a bit lazy.

Yeah, I know what you mean.

Did the link on the volume of the torus help? If you use that what I'd
do is calculate the volume for a torus that completely enclosed the outer
dimensions of the tire and wheel, which would be a bit too big. Then I'd
calculate the value of the largest torus that would fit inside the the
tire and wheel.

Then your true volume would have to be between the two values. I'd take
a simple average of the two volumes and that ought to be awfully close
to the true volume.

Another sneaky method would be to fill a tub with water and have an
overflow tray under it. Submerge the mounted tire in water and measure
how much water overflowed. Then do the same for just the wheel.

Then the gas volume would be = Volume Full Tire - Volume of the wheel

If you really want to be precise immerse just the tire alone and
subtract that volume from what you got above. If you are careful that
should be accurate within 1%-3%

That's a lot of work though.

--
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