Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Done with Co2.

Reply

Old 09-10-06, 11:08 AM
  #26  
roadfix
hello
 
roadfix's Avatar
 
Join Date: May 2003
Location: Los Angeles
Posts: 18,597
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 122 Post(s)
I've never experienced an O ring problem and I've been using CO2's since the mid nineties.
roadfix is offline  
Reply With Quote
Old 09-10-06, 11:12 AM
  #27  
Blaireau
Senior Member
 
Blaireau's Avatar
 
Join Date: Jul 2006
Posts: 1,309
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I ride on Armadillo tyres with oversized thorn resistant tubes, heavy as hell, yes --but I don't even have to worry about the whole Co2. vs Pump debate :-) ...I could ride on a flat in the unlikely event I had one
Bonus: some of the weight gained by the tyres and chambers is lost by ditching the pump/Co2. apparatus....
Blaireau is offline  
Reply With Quote
Old 09-10-06, 11:17 AM
  #28  
humble_biker
so much for physics
 
humble_biker's Avatar
 
Join Date: Aug 2006
Location: over there
Posts: 562

Bikes: Scott CR1 team, Fuji track pro, NYCbike, Cannondale, Free Spirit, GT Edge

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Originally Posted by operator
Not for the gram counters.
It's not a race. I carry a very small pump, two tubes, Park tool patches, and two CO2 cartridges. No way am I walking or hitching a ride. Or anybody I ride with, or see on the road stranded. Unless I'm training, then I can't stop to help. Don't want my heart rate to fall below 185bpm. <;^)
Incidentally CO2 is compressed air, meaning that when it exits the cartridge and enters the tube it expands to larger than the normal CO2 molecule(!). It usually takes the molecules around 24 hours to shrink to normal size. That is why you will have a flat or soft tire the next day after using CO2.
humble_biker is offline  
Reply With Quote
Old 09-10-06, 11:28 AM
  #29  
khuon
DEADBEEF
 
khuon's Avatar
 
Join Date: Aug 2002
Location: Catching his breath alongside a road near Seattle, WA USA
Posts: 12,234

Bikes: 1999 K2 OzM, 2001 Aegis Aro Svelte

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Originally Posted by humble_biker
Incidentally CO2 is compressed air, meaning that when it exits the cartridge and enters the tube it expands to larger than the normal CO2 molecule(!). It usually takes the molecules around 24 hours to shrink to normal size. That is why you will have a flat or soft tire the next day after using CO2.
?!?!?!?!?!?!?!?!?!?! WHAT ?!?!?!?!?!?!?!?!?
__________________
1999 K2 OzM 2001 Aegis Aro Svelte
"Be liberal in what you accept, and conservative in what you send." -- Jon Postel, RFC1122
khuon is offline  
Reply With Quote
Old 09-10-06, 11:30 AM
  #30  
roadfix
hello
 
roadfix's Avatar
 
Join Date: May 2003
Location: Los Angeles
Posts: 18,597
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 122 Post(s)
Originally Posted by khuon
?!?!?!?!?!?!?!?!?!?! WHAT ?!?!?!?!?!?!?!?!?
That was my reaction too.....
roadfix is offline  
Reply With Quote
Old 09-10-06, 12:07 PM
  #31  
DrPete 
Dirt-riding heretic
 
DrPete's Avatar
 
Join Date: Aug 2005
Location: Gig Harbor, WA
Posts: 17,415

Bikes: Lynskey R230/Red, Blue Triad SL/Red, Cannondale Scalpel 3/X9

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Originally Posted by humble_biker
Incidentally CO2 is compressed air, meaning that when it exits the cartridge and enters the tube it expands to larger than the normal CO2 molecule(!). It usually takes the molecules around 24 hours to shrink to normal size. That is why you will have a flat or soft tire the next day after using CO2.
Uh, no. Just no.
__________________
"Unless he was racing there was no way he could match my speed."
DrPete is offline  
Reply With Quote
Old 09-10-06, 12:22 PM
  #32  
Talewinds
Senior Member
 
Talewinds's Avatar
 
Join Date: Oct 2005
Posts: 1,154

Bikes: (2) 2004 Trek 1500, Team Colors:2004 Cannondale Ironman w/ Renn and Zipp: 2005 Kestrel Talon SL: 2001 GT Agressor: 2001 Schwinn Moab: 2001 Specialized S-Works M4 Festina Team Bike: 2002 Pinarello Prince: 1980 Schwinn Voyageur 11.8

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Originally Posted by humble_biker
Incidentally CO2 is compressed air, meaning that when it exits the cartridge and enters the tube it expands to larger than the normal CO2 molecule(!). It usually takes the molecules around 24 hours to shrink to normal size. That is why you will have a flat or soft tire the next day after using CO2.
OHHHH MYYYYYY GODDDDDDDD!
Probably majored in the arts.
Talewinds is offline  
Reply With Quote
Old 09-10-06, 12:47 PM
  #33  
merlinextraligh
pan y agua
 
merlinextraligh's Avatar
 
Join Date: Aug 2005
Location: Jacksonville
Posts: 30,329

Bikes: Wilier Zero 7; Merlin Extralight; Co-Motion Robusta; Schwinn Paramount; Motobecane Phantom Cross; Cervelo P2; Motebecane Ti Fly 29er; Calfee Dragonfly Tandem

Mentioned: 12 Post(s)
Tagged: 0 Thread(s)
Quoted: 865 Post(s)
CO2 does leak out of a tube faster than ambient air which is mostly nitrogen. However, that isn't the explanation for why.
merlinextraligh is offline  
Reply With Quote
Old 09-10-06, 01:30 PM
  #34  
DrPete 
Dirt-riding heretic
 
DrPete's Avatar
 
Join Date: Aug 2005
Location: Gig Harbor, WA
Posts: 17,415

Bikes: Lynskey R230/Red, Blue Triad SL/Red, Cannondale Scalpel 3/X9

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Damned infernal shrinking molecules...
__________________
"Unless he was racing there was no way he could match my speed."
DrPete is offline  
Reply With Quote
Old 09-10-06, 02:40 PM
  #35  
Boss Moniker
It's an old photo
 
Boss Moniker's Avatar
 
Join Date: Aug 2006
Location: Entropia
Posts: 774

Bikes: Cannondale R500, Specialized Hardrock

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
CO2 isn't air, merely a component of air (carbon dioxide), that accounts for like 2% by volume. Air is primarily Nitrogen (like 78%, but I forget the actual figures), and Oxygen. I don't know where you got that description, but it appears to be wrong on all counts (although I'm no expert).

The Co2 in the canisters is compressed under pressure to a liquid, so as it expands it absorbs heat. Each molecule doesn't "expand", merely the spaces in between, when the CO2 goes from a high pressure environment to a lower one.

Of course, this doesn't necessarily explain why the C02 leaks quicker than anything else. I'm relatively certain air isn't a molecule (merely a gaseous mixture), so we can't really compare the "sizes" of molecules.

And you know, the O-ring failure might be a result of the ring being cooled rapidly as the Co2 flows by, which would dry it out and crack it. I guess oiling it heavily with silicone or something might help, or just keep a spare packet of o-rings that you use once each.
Boss Moniker is offline  
Reply With Quote
Old 09-10-06, 04:51 PM
  #36  
khuon
DEADBEEF
 
khuon's Avatar
 
Join Date: Aug 2002
Location: Catching his breath alongside a road near Seattle, WA USA
Posts: 12,234

Bikes: 1999 K2 OzM, 2001 Aegis Aro Svelte

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Originally Posted by humble_biker
Incidentally CO2 is compressed air, meaning that when it exits the cartridge and enters the tube it expands to larger than the normal CO2 molecule(!). It usually takes the molecules around 24 hours to shrink to normal size. That is why you will have a flat or soft tire the next day after using CO2.
I suppose I should say something insightful rather than simply reacting...

Okay. Let's start with the Ideal Gas Law which is:

PV=nRT

Where:
  • P = Pressure
  • V = Volume
  • n = number of moles
  • R = Universal gas constant
  • T = Temperature
We assume for now that this is a closed system which is not entirely true as we will see later. Thus we have:

Pcyl Vcyl / ncyl R Tcyl = Ptube Vtube / ntube R Ttube

Now n is a constant and is fixed (ncyl = ntube) as of course is R, thus our relationship becomes:

Pcyl Vcyl / Tcyl = Ptube Vtube / Ttube

Initially Pcyl > Ptube. As the gas from the cylinder flows into the tube, Ptube starts to go up and Pcyl starts to decrease. However, bear in mind that Vtube also increases. Because Vcyl is fixed, in order to preserve the relationship, Tcyl must decrease. This is why the cylinder gets cold.

The gas expands from a smaller volume in the cylinder to a larger volume in the tube. The ratio of this expansion combined with the initial pressure in the cylinder directly governs the final pressure inside the tube when everything has come to equilibrium. The molecules of the gas do not expand or shrink. The space between them does. All molecular sizes are governed by the composition of their atoms and their atomic bonds.

Now we come to why tyres filled with CO2 go flat faster than with air. CO2 molecules are more permeable and soluable in butyl rubber than other molecules in air. Thus when a tube is filled with air, the CO2 molecules will tend to permeate and leak through the rubber faster than the other components of other gases in the air. This leaves other gasses such as Nitrogen and Oxygen (amongst others) to linger around longer. When a tube is filled with just CO2, the rate of leakage is the same as that of the CO2 leaking out through the tube filled with air but since there's only CO2 to leak, the tube will go flat faster.

BTW, CO2 doesn't necessarily leak through rubber faster because of its size but because of how the molecules in rubber attract CO2 better than Oxygen or Nitrogen. As a result, the CO2 permeates the rubber which then swells and thus allows more molecules to escape.

Note - Writing equations with vBcodes sucks!
__________________
1999 K2 OzM 2001 Aegis Aro Svelte
"Be liberal in what you accept, and conservative in what you send." -- Jon Postel, RFC1122
khuon is offline  
Reply With Quote
Old 09-10-06, 05:00 PM
  #37  
roadfix
hello
 
roadfix's Avatar
 
Join Date: May 2003
Location: Los Angeles
Posts: 18,597
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 122 Post(s)
Originally Posted by khuon
Okay. Let's start with the Ideal Gas Law which is:

PV=nRT
Thanks, now I understand why my coke goes flat sitting out after a couple of hours....
roadfix is offline  
Reply With Quote
Old 09-10-06, 06:50 PM
  #38  
DieselDan
Senior Member
 
DieselDan's Avatar
 
Join Date: Mar 2003
Location: Beaufort, South Carolina, USA and surrounding islands.
Posts: 8,522

Bikes: Cannondale R500, Motobecane Messenger

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Always carry a pump. For all you weight weenies out there, a pump can weight less then 1 lb., but the bike weight upwards of 16-23 pounds, which you will have to carry or push with the flat, when you don't carry a pump.
DieselDan is offline  
Reply With Quote
Old 09-11-06, 08:23 AM
  #39  
DrPete 
Dirt-riding heretic
 
DrPete's Avatar
 
Join Date: Aug 2005
Location: Gig Harbor, WA
Posts: 17,415

Bikes: Lynskey R230/Red, Blue Triad SL/Red, Cannondale Scalpel 3/X9

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Originally Posted by The Fixer
Thanks, now I understand why my coke goes flat sitting out after a couple of hours....
Not completely--maybe if you ask nicely khuon will put together a nice summary of vapor pressure and gases in solution.
__________________
"Unless he was racing there was no way he could match my speed."
DrPete is offline  
Reply With Quote
Old 09-11-06, 08:52 AM
  #40  
Phantoj
Certifiable Bike "Expert"
 
Join Date: May 2005
Posts: 5,647
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Hey, you anti-CO2 guys, have you ever experienced a mechanical failure of the pump you've brought along? That would be equally incapacitating.

I've always been a pump user, but I'm thinking about switching over to CO2, not so much for the weight, but because it's quite a bit smaller. Where's a good place to put a pump on a modern road bike?
Phantoj is offline  
Reply With Quote
Old 09-11-06, 09:55 AM
  #41  
'nother
semifreddo amartuerer
 
'nother's Avatar
 
Join Date: Oct 2004
Location: Northern CA
Posts: 4,599

Bikes: several

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Originally Posted by Phantoj
Hey, you anti-CO2 guys, have you ever experienced a mechanical failure of the pump you've brought along? That would be equally incapacitating.

I've always been a pump user, but I'm thinking about switching over to CO2, not so much for the weight, but because it's quite a bit smaller. Where's a good place to put a pump on a modern road bike?
I'm pro-CO2, but I have experienced a mechanical failure on a pump...it was the impetus for me switching to CO2
'nother is offline  
Reply With Quote
Old 09-11-06, 10:31 AM
  #42  
Surferbruce
Senior Member
Thread Starter
 
Surferbruce's Avatar
 
Join Date: Jul 2004
Location: Los Angeles/Aveyron France
Posts: 5,308
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
well sure, all mechanical things can fail, but i'm going off experience. one time i can handle but twice, same thing, is enough to change my habits. the title of post probably should've been "done w/ co2 as my only means...". i'm sure next time i'm in the shop i'll more closely inpect the nozzle designs on the inflators, and if i see something that looks better will probably try it, but only along with a pump out on the road.
Surferbruce is offline  
Reply With Quote
Old 09-11-06, 10:35 AM
  #43  
DrPete 
Dirt-riding heretic
 
DrPete's Avatar
 
Join Date: Aug 2005
Location: Gig Harbor, WA
Posts: 17,415

Bikes: Lynskey R230/Red, Blue Triad SL/Red, Cannondale Scalpel 3/X9

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Genuine Innovations has a pretty cool device out called the "Second Wind" that's basically a CO2 system with an integrated backup pump. Only pumps to a max of 90 psi, but it's enough to limp home.

This was the 1st link to come up: http://www.performancebike.com/shop/....cfm?SKU=16497

Then you'll never be stranded, even when your CO2 molecules shrink
__________________
"Unless he was racing there was no way he could match my speed."
DrPete is offline  
Reply With Quote
Old 09-11-06, 10:39 AM
  #44  
Al1943
Senior Member
 
Join Date: Feb 2005
Location: Oklahoma
Posts: 9,438

Bikes: Trek 5500, Colnago C-50

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Originally Posted by Phantoj
I've always been a pump user, but I'm thinking about switching over to CO2, not so much for the weight, but because it's quite a bit smaller. Where's a good place to put a pump on a modern road bike?
That's why I switched to CO2 back in '98, bought a CF bike that had no pump pegs. Now I'd never go back.

Al
Al1943 is offline  
Reply With Quote
Old 09-11-06, 10:41 AM
  #45  
DrPete 
Dirt-riding heretic
 
DrPete's Avatar
 
Join Date: Aug 2005
Location: Gig Harbor, WA
Posts: 17,415

Bikes: Lynskey R230/Red, Blue Triad SL/Red, Cannondale Scalpel 3/X9

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Originally Posted by Phantoj
Where's a good place to put a pump on a modern road bike?
The jersey pocket.

I have a Silca 2-step Alloy pump that's ridiculously small and works really well. I take it with me on my rides further from civilization, or if the team car (AKA Mollie, my fiancee) isn't available for support in the event of a CO2 failure.
__________________
"Unless he was racing there was no way he could match my speed."
DrPete is offline  
Reply With Quote
Old 09-11-06, 12:15 PM
  #46  
CyLowe97
Up on the Down Side
 
CyLowe97's Avatar
 
Join Date: Mar 2005
Location: Chicago(ish)
Posts: 6,330
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Originally Posted by ovoleg
REAL men use pumps
...And take an extra 5 minutes to get the tire pumped up, while the CO2 user is a mile down the road....

I've got a combo Genuine Innovations Second Wind [as mentioned by Dr. Pete above]. The pump is small, but enough to get the tire inflation started so that an inexpensive unthreaded 12g CO2 can finish the job, or can hand pump it just enough to ride should I for some reason run out of CO2. And it fits in the saddle bag or jersey pocket, no problem.
CyLowe97 is offline  
Reply With Quote
Old 09-11-06, 12:48 PM
  #47  
curiouskid55
Senior Member
 
curiouskid55's Avatar
 
Join Date: Dec 2004
Location: SoCal Baby
Posts: 2,137

Bikes: o5 Specilized roubaix Comp, 06 Tequilo

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Hey here's another possibillity based solely on conjecture (nothing). The valve freezes and expands when the CO2 is released . When you tighten it, it is still cold. When it warms up to ambinet it is a little loose and does not hold pressure as effectively.
curiouskid55 is offline  
Reply With Quote
Old 09-11-06, 01:10 PM
  #48  
GP 
Senior Member
 
GP's Avatar
 
Join Date: May 2004
Posts: 7,625
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
How do you maintain the o-ring in the inflator? Dab of silicone grease?
GP is offline  
Reply With Quote
Old 09-11-06, 01:34 PM
  #49  
Pedal Wench
Senior Member
 
Pedal Wench's Avatar
 
Join Date: Jul 2004
Posts: 2,048
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
I use the Crank Brother's Power Pump. It fits into a small saddlebag with no problems. Used it yesterday to help out some stranded cyclists who used up both of their CO2 cartridges on a tire they pinched while replacing.
Pedal Wench is offline  
Reply With Quote
Old 09-11-06, 01:34 PM
  #50  
Doid23
Senior Member
 
Doid23's Avatar
 
Join Date: Aug 2004
Location: Westchester NY
Posts: 578

Bikes: Merlin Cyrene, 1989 Nishiki International, Specialized Stumpjumer M2 Hardtail, ProFlex 856 Full Suspension

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I'm sorry, I've got to be honest, his explanation was a lot more fun than yours. I'm sticking with the expanding molecule explanation.

Originally Posted by khuon
I suppose I should say something insightful rather than simply reacting...

Okay. Let's start with the Ideal Gas Law which is:

PV=nRT

Where:
  • P = Pressure
  • V = Volume
  • n = number of moles
  • R = Universal gas constant
  • T = Temperature
We assume for now that this is a closed system which is not entirely true as we will see later. Thus we have:

Pcyl Vcyl / ncyl R Tcyl = Ptube Vtube / ntube R Ttube

Now n is a constant and is fixed (ncyl = ntube) as of course is R, thus our relationship becomes:

![/B]
Doid23 is offline  
Reply With Quote

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service