cappuccino911

With tires that large and you weighing so little, you can keep the pressure closer to the minimum if you are riding some rougher roads and want a more comfortable ride or you can pump them up closer to max if you've got smooth surfaces to help with speed but arbitrarily pumping them up to max isn't necessarily a good idea. For example, you will have less cornering ability so high speed and less cornering ability general aren't a good mix!

krome

Anecdotal evidence follows: I've used CO2 for years for both my automotive and bicycle tires. The difference in the diffusion rate of carbon dioxide (CO2) vs Atmospheric air vs nitrogen is negligible. I don't think that outside of a very scientific study, you won't notice a difference. High volume tires are less dependent on frequent fillings and low volume tires are very critical with regards to air pressure.

Why do I use CO2? Because it costs me ~$14 to fill a 20# bottle once or twice a year. Because there is liquid CO2 under pressure, the 20# bottle holds a large volume of CO2. I can run an impact wrench off of it out in the middle of nowhere, without electricity, and still have plenty of gas left to inflate all 4 car tires from empty, and then some left over.

Maintenance costs on an noisy air compressor far exceed my costs (for CO2) for my needs. Do I recommend it for everyone? No. But for me, CO2 has been a great alternative to an air compressor.

The downsides? CO2 attracts mosquitoes. In sufficient volume, it can cause asphyxiation, but with CO2 you usually know it when you're in the danger zone. CO2 is the gas that tells your brain to breathe. Also, it is a greenhouse gas, but if you are going to criticize me for that, quit drinking carbonated beverages. I use the same CO2 as beer keggers and soft drink manufacturers and fountains.

As an aside, Off road 4x4 users use CO2 to inflate their tires for differing conditions. They also use it to run air tools like I do. The reason, large volume of gas in a compact form (liquid under pressure).

Now obviously I don't carry a 20# tank for bicycle tire repairs on the road. I usually use a hand pump.

vol

Thanks for the advice. I haven't measured the pressure yet, but just to know for now, what does minimum pressure feel like using fingers? It can squeeze quite a bit?

nhluhr

That's just a really bad way to check. Once you know what proper pressure feels like to YOU, it might be okay, but my fingers might be stronger than yours so the amount I can squeeze it is probably different than the amount you could squeeze it.

Seriously, get a pump with a gauge.

noglider 

You really don't want to use a gauge, do you?

You can calibrate your fingers SLIGHTLY if you know your strength, your tires, and your needs. Use a gauge first, then squeeze. But even then, you may know what 90 psi (for example) feels like in YOUR tires, you won't be able to find 90 psi in other tires, nor will you be able to tell 60 psi or 120 psi in any tires. So get a gauge and use it whenever you can. If you're out on the road and replacing a punctured tube, we'll let you get by without one.

I use a floor pump with a built in gauge. I can't NOT use the gauge. I don't carry a gauge with me on the road.

cappuccino911

i concur, the old hand test works okay with bmx tires that are running lower pressures you need a gauge

bikinfool

Curious, why not just buy a tank of compressed nitrogen for that matter? What are the cost differences?

cyclist2000

On my road bike I have a pump that has a gauge, I don't want problems when limping home.

vol

I'm sure I'll get a gauge before long (probably one that comes with a floor pump) . But if I could be without it, why bother? What I'd like to know is, if you use fingers's feel, what's the big deal if the actual pressure is a little more or a little less than it should be due to the finger mistake?

nhluhr

Well, with overinflation... you just risk a blowout if the tire/rim can't handle it, a flat due to the rim spoke drilling, rough handling, lack of compliance during cornering (skittering around the corner like an unsharp ski on icy snow), discomfort, etc.

With underinflation the main problem is risk of pinch-flats and certainly there could be some adverse handling traits as the tread squirms around since it isn't as stable.

Carbonfiberboy 

I pump at home every time I ride my bike. My tires will lose a little pressure overnight, and become unrideable in a couple weeks. An excellent reason to pump every time is that you'll find out how many strokes are normal. Then you'll know if you have a slow leak before you go out.

My floor pump has a built-in gauge. After a flat, I pump until the on-bike pump handle feels right. How do I know what that is? I tried it at home and checked with my floor pump. One can also inflate one tire until it feels like the other.

If you squeeze, squeeze the sidewall rather than pushing on the tread. For a road bike, your thumb should be able to press in some, but not much. Not at all squishy, but not like a stone, either. Most on-bike pumps can't overinflate a road tire. But some can. If you think those statements are too vague, you're right.

A gauge is probably more important for MTB tires, since they are really hard to tell by squeezing and proper pressure makes a big difference on technical terrain. OTOH, it's easier to find a gauge for MTB tires than road tires, since they're closer to auto and truck pressures.

krome

Because Nitrogen cannot be stored as a liquid under pressure at "normal" temperatures, with normal being temperatures that humans live at. You'd get a lot less volume of gas with a tank of nitrogen than a comparable tank of CO2 because the CO2 liquefies under pressure. Price difference? I don't know, It is probably insignificant, but you'd need a much larger tank to get an equivalent volume of gas.

cyccommute 

A few things. First, while CO2 is a greenhouse gas, the stuff you get from dry ice (solid CO2) or liquified CO2 is separated from the air so the net effect is zero. The CO2 you get from the tailpipe of your fossil burning automobile is bad stuff because that carbon was removed from the atmosphere millions of years ago. The net effect of adding it to the atmosphere is not zero.

CO2 in bicycle tires is not the same as CO2 in car tires. Bicycle tires are usually lighter, have less rubber and use very thin tubes instead of relying on the tire as the barrier. Using thin tubes will allow any gas to permeate out faster. CO2 just happens to be more soluble in the rubber than other atmospheric gases by a factor of about 3 over oxygen and by a factor of 6 over nitrogen. With a thick tire, like a car or even a tubeless off-road tire, the rate of solubility is probably slow enough that you wouldn't notice it. With a thin tube like a road bike tire, it would be very noticeable. Most people report a very large rate of deflation using CO2 in bicycle tires. A few hours is usually enough to go from 100+psi to flat.

krome

Gotta disagree with you there. There are a lot of gases obtained through air liquification, but CO2 is a very small fraction (mostly nitrogen, oxygen, and argon, with small amounts of other gases). Most industrial CO2 does not come from atmospheric gases. At least I'm not "wasting" it on paintballing or something

My skinniest tire is a 27x1-1/4. Maybe that is why I don't notice much leakage. All tires leak, low volume ones are very noticeable. I don't run bikes with really skinny tires.

All I can say is, I've used the stuff for years (in the bulk tanks) and have also used compressed air (from an air compressor) and for the size of tires I run, there is no obvious difference in the amount of times I need to fill my tires. I won't disagree with the permeability of CO2 with regards to other gases. I probably never use latex tubes, they are probably butyl.

Using the gram cartridges of CO2 is probably not a cost effective or wise way to keep your tires inflated. I use a bike pump much of the time for the bicycles, but finding a pump that lasts is another topic. For car tires, I use the CO2 tank. Bike pump broken, CO2 tank. Need to run an impact wrench to get that stuck bottom bracket out, CO2 tank.

nhluhr

You seem to have forgotten the fuel/energy used to separate and liquify it....

dahut

I use a tanked compressor. Set the thing for 100 psi, and shoot the tires when it reaches the gauge setting. The tires come up to tank pressure instantaneously and voila! Tires aired up.

cyccommute 

Atmospheric gases are mostly nitrogen and oxygen. The other gases make up such a tiny amount, that they can be all but ignored except for their importance to science and industry. CO2 comes from mostly industrial sources but it's a byproduct...not the main product so the net effect of using it for other applications is still zero. Even 'wasting it' on paintball isn't contributing to overall global climate change.


Most people report a fast deflation when using CO2 on any bicycle tire. I've used the stuff only one or two times myself...a hand pump is just easier and more convenient...but I did notice a significant pressure reduction overnight.

CO2 is soluble in all rubber compounds. It's particularly soluble in natural latex but the solubility values I reported are for butyl rubber.

I agree that using CO2 is not cost effective. You have other applications for a larger CO2 tank so it fits your needs. For most of us, however, a floor pump or a frame pump is still the best way to fix flats and inflate tires.

Considering all the other things done to produce it...burning fossil fuels in particular...the energy to separate and isolate it is pretty minimal.