Does CO2 deflate faster?
secretsam
Posts: 5,120
OK, daft question - I read somewhere that if you are massively lazy and use a CO2 cannister to pump your tyres, they go down quicker 'cos CO2 is "smaller" than regular air so leaks faster - is this true?!?!?!?
(Apologies for lack of technical language)
(Apologies for lack of technical language)
It's just a hill. Get over it.
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It has been many years since I did A level chemistry, and I didn't get a particularly good result, but this sounds like cobblers.
CO2 molecules are bigger than the N2 molecules that are the primary constituent of the earth's atmosphere (and so most of what goes into your tyres with a regular pump).
They would have a point it you were inflating your tyres with Hydrogen or Helium though, as these are very small and difficult to contain, presenting real challenges in storage for airship makers, and hydrogen fuel cells (hence why the Hydrogen fuel-cell economy hasn't really taken off...)0 -
It's not the size of the molecules but that butyl rubber is soluble with CO2, so it just passes straight through the tube.0
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I carry CO2 for roadside punctures, but I always empty the tyre and reinflate with air when I get home.0
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If I remember my A Levels correctly CO2 is much more soluble in water than O2 or N2 (which are the main constituents of air) - if you have inflated with a normal pump many times and slowly you have got a fair amount of water condensed out inside the tube itself then I suppose that more CO2 would dissolve
edit / Back of envelope calculations would be that
- 1g of water could dissolve 2.5e-3g of CO2
- this is about .00005 of a mole
- which is just under 1.2cm^3 at one bar
- which will be about .2cm^3 at six bar
So no difference at all unless you have a decent amount of water in there. Not sure if CO2 would react to the rubber in some way - but I think this is very unlikely0 -
OK, daft question - I read somewhere that if you are massively lazy and use a CO2 cannister to pump your tyres, they go down quicker 'cos CO2 is "smaller" than regular air so leaks faster - is this true?!?!?!?
(Apologies for lack of technical language)
IME it is certainly true that a tyre pumped with CO2 loses pressure much faster than one pumped with atmospheric air. Don/t know why.0 -
No. A CO2 molecule is larger than oxygen or nitrogen molecules.OK, daft question - I read somewhere that if you are massively lazy and use a CO2 cannister to pump your tyres, they go down quicker 'cos CO2 is "smaller" than regular air so leaks faster - is this true?!?!?!?
(Apologies for lack of technical language)
Gasses can permeate through membranes, but inner tubes are pretty thick and the real world effect is small.
This sort of notion comes from using latex tubes (a much more open structured polymer than butyl, and the tubes themselves are also generally far thinner).
Hypothetically, CO2 has polar qualities that could be relevant to its membrane permeability. However, you would be looking at a small change in a small effect, as compared to oxygen and nitrogen (and for that matter I have no idea in which direction).0 -
Confirmation bias?[url=http://www.bikeradar.com/forums/viewtopic.php?p=19772226#p19772226]Greg66 Tri v2.0[/url] wrote:OK, daft question - I read somewhere that if you are massively lazy and use a CO2 cannister to pump your tyres, they go down quicker 'cos CO2 is "smaller" than regular air so leaks faster - is this true?!?!?!?
(Apologies for lack of technical language)
IME it is certainly true that a tyre pumped with CO2 loses pressure much faster than one pumped with atmospheric air. Don/t know why.0 -
It's not the size of the molecules but that butyl rubber is soluble with CO2, so it just passes straight through the tube.
Ah - didnt know that! Confirmation below
http://velonews.competitor.com/2009/02/bikes-and-tech/technical-qa-with-lennard-zinn-large-molecules-and-short-frames_871750 -
Whenever this subject has been discussed in the past the consensus is always yes, co2 does deflate noticeably faster than air.
Using co2 is not a sign of being massively lazy, it's more convenient and a couple of carts in with the spare tube & patches is neater than a pump attached to the frame. A phone or cash for a taxi covers the unlikely chance of too many punctures on a ride.0 -
Interesting stuff. I've never really used CO2 so hadn't had a chance to notice!
More Convenient = better for lazy peopleUsing co2 is not a sign of being massively lazy, it's more convenient and a couple of carts in with the spare tube & patches is neater than a pump attached to the frame. A phone or cash for a taxi covers the unlikely chance of too many punctures on a ride.
There's plenty of room for a decent pump in my bag so I carry one on the commute, I'm a tightwad and it's free to use... Other rides I frame mount and to hell with the ugliness.0 -
Edit: That article has a few issues. It points to an academic discussion forum answer relating to a natural rubber balloon - which is neither (necessarily) the same material as a latex tube, or butyl. An inner tube is also orders of magnitude thicker than a balloon and so the gas permeation rate will be commensurately smaller for an inner tube. Also, the "expert" says, "...and is thus not constrained to normal permeation loss, it can transfer straight through the bulk rubber.." What's "normal" permeation loss then, if it is not "transfer through the bulk rubber? He is making a distinction where there is none, which might infer that he has no idea what he's talking about.It's not the size of the molecules but that butyl rubber is soluble with CO2, so it just passes straight through the tube.
Ah - didnt know that! Confirmation below
http://velonews.competitor.com/2009/02/bikes-and-tech/technical-qa-with-lennard-zinn-large-molecules-and-short-frames_87175
He is also proffering an explanation which doesn't really fit the observations. You will note that the original question in the Velonews article mentions that the pressure initially drops rapidly and, "Since then, it has not dropped significant pressure in a week."
I would take some convincing to be persuaded that such leakage from an inner tube is anything other than substantially due to the metal/rubber interfaces at valve and valve stem. One highly significant difference between inflating a tube with a canister as opposed to a pump or compressor, is temperature. CO2 goes in cold. Very cold. So you have the added factors of the freezing of and condensation on, sealing surfaces, which one subsequently press together to hold the gas in. Not ideal for sealing against a high pressure differential.0 -
It's easier and quicker to get a tube to 90-100psi with a cart than a minipump at the roadside, and if you buy the things from leisure & catering suppliers they're effectively free - I paid < £20 incl p&p for a box of 32 a few years ago and still have most of them. It's as good as a lifetime's supply for one small outlay, as opposed to 3 for a tenner in a blister pack in Evans.Interesting stuff. I've never really used CO2 so hadn't had a chance to notice!
More Convenient = better for lazy peopleUsing co2 is not a sign of being massively lazy, it's more convenient and a couple of carts in with the spare tube & patches is neater than a pump attached to the frame. A phone or cash for a taxi covers the unlikely chance of too many punctures on a ride.
There's plenty of room for a decent pump in my bag so I carry one on the commute, I'm a tightwad and it's free to use... Other rides I frame mount and to hell with the ugliness.0 -
Interesting stuff. I've never really used CO2 so hadn't had a chance to notice!
More Convenient = better for lazy peopleUsing co2 is not a sign of being massively lazy, it's more convenient and a couple of carts in with the spare tube & patches is neater than a pump attached to the frame. A phone or cash for a taxi covers the unlikely chance of too many punctures on a ride.
There's plenty of room for a decent pump in my bag so I carry one on the commute, I'm a tightwad and it's free to use... Other rides I frame mount and to hell with the ugliness.
You stick with wanking your pump, I'll stick with being able to pop my tyres back to pressure very quickly and then cracking on with the ride. I know I'd rather be getting fitter legs than forearms
Trail fun - Transition Bandit
Road - Wilier Izoard Centaur/Cube Agree C62 Disc
Allround - Cotic Solaris0 -
I have a pump about the size of two CO2 canisters. It gives me access to an unlimited amount of compressed air. I just can't get my head around the concept of substituting that for a limited about of CO2, certainly when it comes to commuting.
It's easier and quicker to get a tube to 90-100psi with a cart than a minipump at the roadside, and if you buy the things from leisure & catering suppliers they're effectively free - I paid < £20 incl p&p for a box of 32 a few years ago and still have most of them. It's as good as a lifetime's supply for one small outlay, as opposed to 3 for a tenner in a blister pack in Evans.Interesting stuff. I've never really used CO2 so hadn't had a chance to notice!
More Convenient = better for lazy peopleUsing co2 is not a sign of being massively lazy, it's more convenient and a couple of carts in with the spare tube & patches is neater than a pump attached to the frame. A phone or cash for a taxi covers the unlikely chance of too many punctures on a ride.
There's plenty of room for a decent pump in my bag so I carry one on the commute, I'm a tightwad and it's free to use... Other rides I frame mount and to hell with the ugliness.
I always seem to get a flat when its wet and dark. Its somewhere between impossible and pot luck as to whether I can find the microscopic piece of glass that caused a puncture amongst all the other sh!t on my gloves and tyres. So I'll normally patch a tube first in case I've missed the cause and I certainly wouldn't want to use up my only inflator under those circumstances.
Plus CO2 leaks way faster.0 -
I have a pump about the size of two CO2 canisters. It gives me access to an unlimited amount of compressed air. I just can't get my head around the concept of substituting that for a limited about of CO2, certainly when it comes to commuting.
I always seem to get a flat when its wet and dark. Its somewhere between impossible and pot luck as to whether I can find the microscopic piece of glass that caused a puncture amongst all the other sh!t on my gloves and tyres. So I'll normally patch a tube first in case I've missed the cause and I certainly wouldn't want to use up my only inflator under those circumstances.
Plus CO2 leaks way faster.
Each to their own, but I find minipumps are Ok for getting you up to say 60psi, but anything beyond that and you need to be Popeye, and frankly it's a massive PITA. Perhaps I should dig out a proper frame-fit pump, which I recall were half-way decent!
It's just a hill. Get over it.0 -
You do it your way First, I'll do it mine. I get a couple of punctures a year on average [except for a flurry on some wafer-thin tyres a couple of years ago]. The last two involved one as I left the office, and one as I rolled onto my drive at home so neither mattered. The last non-commute flat was a brief interruption as the thorn was readily identifiable, the guy I was riding with hadn't seen co2 before and was well impressed at the speed, simplicity and lack of grunting that would be needed to get a pump the size of a parsnip to push enough air into a 23c tube. One cart, remove thorn, swap tube, a quick psssssssttttt and we're away. It also reduces the possibility of breaking the valve stem in the final few pushes as the effort required intensifies to get it up to a decent pressure.
I keep a track pump here in my office and at home and replace co2 with air as soon as is reasonable. As stated co2s are free - £20 some years ago is an irrelevance now. It may all go wrong one day and I'll find myself with no carts left - if so I'll deal with it, but it hasn't happened yet.0 -
I only run about 85psi normally anyway and 60-70psi is fine for the end of a ride/commute and way better than zero. The big PITA is flatting, figuring out why and fixing it. The 2 mins it takes to put 150-200 pump strokes phnarr into a tube is neither here nor there. But I am good with a pump.I have a pump about the size of two CO2 canisters. It gives me access to an unlimited amount of compressed air. I just can't get my head around the concept of substituting that for a limited about of CO2, certainly when it comes to commuting.
I always seem to get a flat when its wet and dark. Its somewhere between impossible and pot luck as to whether I can find the microscopic piece of glass that caused a puncture amongst all the other sh!t on my gloves and tyres. So I'll normally patch a tube first in case I've missed the cause and I certainly wouldn't want to use up my only inflator under those circumstances.
Plus CO2 leaks way faster.
Each to their own, but I find minipumps are Ok for getting you up to say 60psi, but anything beyond that and you need to be Popeye, and frankly it's a massive PITA. Perhaps I should dig out a proper frame-fit pump, which I recall were half-way decent!0 -
Ah, now, there was a thread somewhere here about pointless innovations in cycling.You do it your way First, I'll do it mine. I get a couple of punctures a year on average [except for a flurry on some wafer-thin tyres a couple of years ago]. The last two involved one as I left the office, and one as I rolled onto my drive at home so neither mattered. The last non-commute flat was a brief interruption as the thorn was readily identifiable, the guy I was riding with hadn't seen co2 before and was well impressed at the speed, simplicity and lack of grunting that would be needed to get a pump the size of a parsnip to push enough air into a 23c tube. One cart, remove thorn, swap tube, a quick psssssssttttt and we're away. It also reduces the possibility of breaking the valve stem in the final few pushes as the effort required intensifies to get it up to a decent pressure.
I keep a track pump here in my office and at home and replace co2 with air as soon as is reasonable. As stated co2s are free - £20 some years ago is an irrelevance now. It may all go wrong one day and I'll find myself with no carts left - if so I'll deal with it, but it hasn't happened yet.
When I were a lad, bike pumps came with a little flexible threaded hose sored in then end to connect the pump to the valve. Then there came the new innovation of pumps with a rigid quick release connector, which help the user to bend the valve end.
More recently, I've seen pumps with threaded flexible hoses stored inside them to avoid such problems. :roll:0 -
One small saddle bag containing a tube, a couple of patches + glue + sandpaper, and a couple of co2 carts and the valve. I put the bag on whichever bike I'm riding (mounting clip on each see?). On the extremely rare event that a tyre flats, it's an easy job to resolve it and get going again. It's not life changing, there is no right answer just whatever suits an individual. Personally I prefer to get the tyre up to full pressure quickly and easily and get going again, rather than use a pump and announce "that'll do" and do the rest of the ride hoping not get a pinch flat, or having to do a Charles Atlas to get enough pressure in. I prefer to enjoy cycling, and a co2 adds to it if a flat happens - it's a neat quick solution, albeit one with limitations that I haven't yet hit. If suddenly after years of not being bothered about the odd puncture I start having lots, I'd probably rethink my tyre choice, puncture repairing abilities or reading of the road rather than revert to a pump hanging off the bike. Each to their own though.0 -
This is a further part of the equation for me - I'm a big bastard and 90-100psi on a road tyre is inadequate - well, ok at the front but certainly inadequate for the rear for any distance. I use a hybrid pump (knockoff of a topeak morph) and 120psi is achievable without much bother.
It's easier and quicker to get a tube to 90-100psi with a cart than a minipump at the roadside, and if you buy the things from leisure & catering suppliers they're effectively free - I paid < £20 incl p&p for a box of 32 a few years ago and still have most of them. It's as good as a lifetime's supply for one small outlay, as opposed to 3 for a tenner in a blister pack in Evans.Interesting stuff. I've never really used CO2 so hadn't had a chance to notice!
More Convenient = better for lazy peopleUsing co2 is not a sign of being massively lazy, it's more convenient and a couple of carts in with the spare tube & patches is neater than a pump attached to the frame. A phone or cash for a taxi covers the unlikely chance of too many punctures on a ride.
There's plenty of room for a decent pump in my bag so I carry one on the commute, I'm a tightwad and it's free to use... Other rides I frame mount and to hell with the ugliness.0 -
Perhaps I'll give CO2 a go for weekend rides and sportives....
I've had 4 flats this winter already. Okay, so my tyres were old, but the main reason is that I live in Scotland and Irn Bru still comes in glass bottles.0 -
OK, daft question - I read somewhere that if you are massively lazy and use a CO2 cannister to pump your tyres, they go down quicker 'cos CO2 is "smaller" than regular air so leaks faster - is this true?!?!?!?
(Apologies for lack of technical language)
Do you mean when at home? That would be seriously dumb and expensive, as stated before co2 leaks through rubber and should only be used by the roadside.
As for TW question about pressure a 16g cartridge should be good for 120+ psiRule #5 // Harden The Feck Up.
Rule #9 // If you are out riding in bad weather, it means you are a badass. Period.
Rule #12 // The correct number of bikes to own is n+1.
Rule #42 // A bike race shall never be preceded with a swim and/or followed by a run.0 -
Whatever the reason, CO2 definitely leaves tyres softer the night after you put it in. Like others, I always empty the tyre and refill with air on returning home.
And CO2 is a fab way of doing this. Frankly I've seen far more problems (both my own but mostly others) caused by pumps - the direct-connecting ones busting valves and the pumps with hoses taking the valve out after all the work. These days I ride regular rides with 2 cartridges and no pump. I'll take a pump with me on epic rides and only if no-one else has.ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH0 -
Oh god, this should be in the my rants thread, but why oh why do some tubes come with screw in valve bodies? I can get them back in using my chain tool but one day I'll be arrested for breach of the peace when it happens.Whatever the reason, CO2 definitely leaves tyres softer the night after you put it in. Like others, I always empty the tyre and refill with air on returning home.
And CO2 is a fab way of doing this. Frankly I've seen far more problems (both my own but mostly others) caused by pumps - the direct-connecting ones busting valves and the pumps with hoses taking the valve out after all the work. These days I ride regular rides with 2 cartridges and no pump. I'll take a pump with me on epic rides and only if no-one else has.
You are making me seriously consider the 2xtube and 3xcanister option for longer dry rides. Not for a commute through zero mobile coverage areas though.0 -
I did a ride with Rapha in NL last year. Horrible wet day, we got 7 punctures between 4 of us. The ride lead managed to unscrew the valve 3 times - I learned some new Dutch swear words ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH0
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aren't they just English swear words but with a lisp?I did a ride with Rapha in NL last year. Horrible wet day, we got 7 punctures between 4 of us. The ride lead managed to unscrew the valve 3 times - I learned some new Dutch swear words0
