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I have a frame pump that I've used on the road when replacing flats, but I always see CO2 inflators advertised at bike shops. Are they worthwhile for the potential weight savings?

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I won't add this as an answer because I'm not positive it's the case, but I think a tire inflated with a CO2 inflater will deflate quicker, because of the increased difference in partial pressure of CO2 between the inside and outside of the wheel. This depends on how permeable CO2 is through rubber, though - it could very well be the reverse. –  Nick Johnson Dec 21 '11 at 23:09
    
I generally don't see the point of CO2 inflators, but I did encounter one use for them recently. I had a flat and attempted to reinflate the leaky tire with my hand pump in 95F weather, in order to make the last mile home. With the CO2 inflator I'd have known right away, without much effort, that it was a lost cause, vs working up an additional useless sweat with the hand pump. –  Daniel R Hicks Jul 12 '12 at 2:44
    
@freiheit Just a minor quibble with your answer. CO2 is not a smaller molecule than N2. It does leak out, though, due to the partial pressure difference between the inside and outside of the (slowly) permeable tyre. :-) –  user6416 Mar 20 '13 at 1:30
    
i believe that the best realisation for co2 canisters are for city bikers who park up over a day.. Who would want to steal a bike with flat tyres or goto the hassle of pumping up then stealing! Deflate your tyres, park and lock and re-inflate when you come back after work or doing what ever you were doing without a worry! What we would need to do is design a unique nozzle for each valve, kind of like a key that fits in a lock.. that way not anyone with a canister could do the same and still steal..! –  user7843 Aug 18 '13 at 20:53
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@DonaldRoss That would be some expensive theft prevention if you need one (or even more) CO2 canister per day. Above that it doesn't look as if your answer doesn't try to answer the question, if the CO2 inflators are worth the weight savings. –  Benedikt Bauer Aug 19 '13 at 14:14
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13 Answers

up vote 36 down vote accepted

Advantages:

  • Fast - generally these fill up your tire much faster than you could with a pump
  • Less effort - hook up, push button, no pumping
  • Possibly less weight (but I haven't compared weight of smallest pumps to CO2)
  • Lower initial investment - a valve and 2 cartridges generally seems to be cheaper than a good small pump.

Disadvantages:

  • Consumable cartridges - which is a cost issue if you have to fill up often
  • No backup - if you patch a flat and don't get it quite right, you don't have a way to fill up anymore. You could carry extra CO2 cartridges, but then you could lose the weight advantage.
  • Limited on what tires they work with. Big tires will get less pressure.
  • Less friendly - if your friend gets a flat and you've got one cartridge, will you loan it? If you've got a pump it's no problem at all. I've helped out complete strangers with my pump before.
  • Goes low faster. CO2 seeps through the tube a bit faster than air, so you'll have to top off the tire sooner than if you'd used a pump.

One possibility to consider is a combo unit. Generally the pump on those is terrible, but it should be enough to get you home if you run out of CO2. Or carry both a pump and a CO2 valve and a cartridge. That way your first flat can be fixed super-fast and you avoid all the disadvantages (and the weight of a simple valve and one cartridge isn't much).

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This fits pretty well with my experience. Nice answer! –  Neil Fein Sep 4 '10 at 21:32
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Another potential disadvantage: it's very possible to explode the inner tube when using the CO2 cartridges on a road bike. I have done this before, and then you are out of air, and the tube is completely destroyed (you can't patch it). –  kevins Sep 5 '10 at 19:44
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+1 Kevin. So you should also have a seat bag with a spare inner tube. Over the years my bag has grown with its contents; a couple of gels, a couple of CO2 cartridges, multitool, photocopy of my driver's license (so I don't need a wallet in my jersey), $20 bill just in case. –  Jay Sep 13 '10 at 21:41
    
Yep, I generally have at least two spare tubes. Patching a tube on the shoulder in the cold rain or hot sun is not something I enjoy. –  Daniel R Hicks Nov 30 '11 at 18:29
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FWIW, you can inflate mountain bike tires with 12-16g CO2 cartridges without issue. I've also used them for cross tires. The increased volume of air is usually covered since you are not inflating to the same pressure. –  Rob Dec 1 '11 at 0:40
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The main benefit that I get from using a CO2 inflater over using a pump is time savings. The CO2 will fill your tire with air faster than a pump.

I always carry a pump in addition to a CO2 inflater because the pump provides unlimited air. It's a good idea to be prepared to handle at least 2 flats so the pump is a nice backup.

I would consider just carrying a CO2 inflater during a race for the weight savings which negligible.

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How fast is a CO2 and how fast is a pump? Raw numbers may be more useful –  Joe Philllips Sep 5 '10 at 19:11
    
Sorry, I don't have raw numbers. Several variables. For CO2 it would depend on how easy the CO2 adapter is to attach to the valve stem. It's just a matter of seconds to inflate the tire once the CO2 is released into the tire. The amount of time it takes to inflate a tire with a pump depends on the pump. Some pumps provide more air volume per stroke than others. Usually takes me a few minutes using a small portable pump to fill up my mountain bike tire. –  jenglert Sep 7 '10 at 2:46
    
@Joe the CO2 inflaters are almost instantaneous, you'll have a solid 100psi tyre within 1-2 seconds. Faster than any hand pump you could carry with you. –  Unsliced Sep 15 '10 at 9:07
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Not to mention, good luck getting to 100psi with a hand pump. It's tedious even getting to 50psi. –  Stephen Touset Jun 17 '11 at 15:28
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Bike shops advertise them because they're consumable items. Every time you use a cartridge the shop is likely to make another sale. Whereas a good pump should last through many, many flats and is less likely to get good placement in the shop.

For advantages/disadvantages, see freiheit's answer.

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Disadvantage: Environmentally irresponsible.

It seems to me that there is a lot of energy contained within, and required to make, that CO2 cartridge for a single tyre inflation.

I do carry one for emergencies 'in case of pump failure' but I try my best to never use it out of laziness.

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Not that it counter acts all of the negatives, but most cartridges are recyclable. –  Rob Dec 1 '11 at 0:42
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I'm surprised nobody else has mentioned this. Probably the most legitimate purpose of CO2 inflators for bicycles is for inflating tubeless tires. If you need to replace or repair a tubeless tire, chances are you will have zero luck inflating the tire if you try to use a hand pump. You either need to use an air compressor (good luck carrying that with you on your rides) or a CO2 inflator. This is because tubeless tires need a sudden and rapid burst of air in order to become inflated. It's the only way to get a tight enough seal between the rim and tire. Otherwise, when initially inflating the tire, air will escape from the tire as fast (or faster) than you can pump it in by hand.

Once a tubeless tire has sufficient pressure in it to maintain an airtight seal, then a hand pump may be used to inflate it the rest of the way (and to keep it inflated).

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The CO2 inflater is, for me, only an emergency option. It lives in my saddle bag to get me home after a flat.

I haven't rigorously investigated it, but anecdotally I think that tyres inflated with CO2 deflate by themselves more quickly than air-inflated tyres do. Fortunately I haven't punctured too much recently, but the last couple of roadside fixes with CO2 inflation have deflated overnight which, when re-inflated with air, have been fine (i.e. no secondary punctures).

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That depends... I usually carry inflaters AND a pump. I've had problems with both. The CO2 cartridges aren't too crazy expensive, but my most recent flat I used 2 of them and still ended up finishing with the pump. It's really easy to blow the CO2 out without getting it in the tire, and if that happens, you'd better have another cartridge to try, or a pump on standby for backup. The inflaters seem like a good idea and worked fine at home, but in practice when stuck on the side of the road, I'm unimpressed. The small handpumps I've also found difficult to work with. They just don't latch on as well as a regular pump. I'm still looking for a good reliable solution (which I need 'cause I get a LOT of flats).

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get some 'slimers' and kevlar tyres. –  Mark W Feb 7 '13 at 12:31
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I really like using the co2 canisters cause the're quick to pump up. Particularly for road bike, you can't get a road bike to 110psi using a hand pump. Most I've got is around 40psi with a hand pump. That pressure will let you limp home but certainly you can't continue on your merry ride with that pressue for fear of a low pressure flat. I've also now noticed that the co2 caninsters will do a great job to get it to 110psi and allow you to continue your ride as usual, howowever leave the bike overnight and you're tyre will deflate significantly. I though I had another flat tyre the morning after however checked it all and there were no holes. So the only thing why the tyre went down is cause I used a co2 cartridge. You can get bulk packs of cartridges of ebay for $1.75ea (min of 10 cartridges per transaction), so really not that expensive to carry on every ride.

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I can most definitely get a road bike to 110psi with a hand pump. You just need to get the right pump for the job. –  Daniel R Hicks Dec 17 '11 at 12:52
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CO2 inflators can be a life saver in the winter when you want to spend as little time off the bike as possible or you'll start freezing. That being said, it is a good idea to learn how to use the inflator properly... their operation varies by brand. You wouldn't want to be fumbling on how to operate the inflator in sub zero temps.

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Hand pump is more fitness friendly, remember that when you cycle you use much more your legs than your arms, so when you get a flat please give you arm muscles a chance to workout a little bit as well.

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With regard to your question over potential weight savings, I quickly weighed the kit that I normally use to give a comparison. The mini pump that I carry from Lezyne comes in at 83g (has some subtle modifications to stop it rattling); whereas the two unbrnaded 16g CO2 cannisters that I carry come in at 118g and require a chuck to use which is another 21g. So about 56g heavier all in. Not that significant; but not in the favour of using CO2 unless you carry only one cannister and then you'll make the a 6g saving over the pump.

I don't have a full frame pump for comparison weight wise, but I'd expect it to come in quite a bit heavier than the mini one I carry. That said, I've been able to inflate a road tyre to the correct pressure using it, even if it took quite a long time to do so.

Also, when repairing a puncture it's often useful to partially inflate the inner tube, both to find the puncture and to give a replacement some shape and form. Doing this with CO2 is likely to be quite hard given the limited inflation control that most units provide.

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Only time I've carried CO2 is during mtn bike races. Speed and convince. For road racing there was the support vehicle or worse case situation a dnf. Have only run tubed mtn bike tires and tubular road tires. For recreational riding and training it's a pump. New favorite pump is the large version of the Lezyne Road HP. The narrow dimension allows for easy higher psi pumping and the length for less strokes than the lighter mini pumps. Pump is not that heavy at ~110gm. Personal feeling that CO2 are wasteful for just general tubed tire use. Total weight savings is minimal over a couple CO2 & inflation device. Depending on the number of flats experienced the pump may in the long haul be less of an investment. Plus what happens if no pump & you mess up using the cartridge or run one short?

Sitting in the ditch pulling off a tubular tire and mounting up the spare no matter if it's hot, raining or whatever is no fun. Add having to manually pump up the tire adds to the no fun. But flatting is not supposed to be a good time:)

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If u carry a good pump, there is no need for CO2 cartridges. Get the longest frame pump that will fit, and you will get 110psig in 35 - 45 strokes. How much longer does that take than using a CO2 cartridge? Also, i don't believe that the weight of the pump is significant, unless you are racing. I don't remember exactly, but I think that my Zefal XL pump cost less than $30, and it still works flawlessly after 6+ years.

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