Saturday, January 23, 2016

Co2 Inflation Devices for Motorcycles

My family operates a bicycle repair and accessories business so we are very familiar with Co2 tire inflation devices. I've always thought of them as "bicycle accessories" and as "bicycle operators" we also carry and use them when out on the trails or roads. So you'd think that I'd be able to answer the question about whether these Co2 cartridges would be useful for motorcycles. Honestly, without doing any testing, my knowledge/experience would suggest to me that they would not be effective. But again, I haven't done the testing...until now.

There are a number of motorcycle-specific Co2-based repair kit offerings. One example I recently came across is the BikeMaster Tire and Tube Flat Repair Kit.  This kit seems very comprehensive and has a $50 price tag. I sort of appreciate that it is a repair kit for both tube and tubeless as I personally have two motorcycles; one is tubed and the other is tubeless. As shown in the photo below, the BikeMaster Kit includes 4 Co2 cartridges. However, their website is silent as to the size of the cartridges or what the user can expect from them.

Another repair kit I found was by well-known motorcycle accessory supplier, Pit Posse. The contents of their kit, which goes for $25, is similar to BikeMasters (above) but has only three cylinders. Pit Posse states on their website that each cartridge will inflate a standard front or rear tire. Lastly, some offerings skip the tire repair tools and just sell the inflator and cartridges. An example of that is Tusk, which offers an inflator valve and two cylinders for $12. They state on their website that most motorcycle tires require 1 1/2 cartridges and ATV tires require 2 cartridges.

Again, I've used these inflators and cartridges for years and, as a result, I seriously question these claims that one or two 16g cartridges will inflate a motorcycle tire.

But let's back up with some background info based on what I know from our bicycle business. Everybody rides bicycles, so it provides some useful perspective to the capabilities of the cartridges.

Co2 cartridges generally come in three popular sizes and contain "liquid state" Co2 that is under a great deal of pressure (600-900 psi) in the cartridge. The weight of the liquid-state Co2 is measured in grams (or "g'). When it is opened and released to the atmosphere the Co2 turns to its gaseous state.

The three sizes and how we apply them to bicycling are as follows:
  • 12g Cartridge: Suitable for inflating one small mountain bike tire.
  • 16g Cartridge: Suitable for inflating one medium sized mountain bike tire.
  • 25g Cartridge: Suitable for inflating one road bike, or 700c and or large 29r mountain bike tire.
My current road bicycle is a 2012 full carbon Litespeed C1 as shown in the stock photo below. This bicycle has the very thin 700c tires/tubes that I run normally at the manufacturer recommended 100-110 psi. I carry 25g cartridges and have had to use them on several occasions when I blew out a tire. The 25g cartridges will only fill one of those tiny tubes up to about 60 psi.

Given the nature of how the Co2 cartridges apply to bicycle tires of different sizes, it really seems that a motorcyclist is going to need a bunch of them to get their motorcycle tires inflated. This is simple ... a motorcycle tire requires much more volume of air (or other gas ... Co2, Nitrogen as examples) than bicycle tires. So if a 16g cartridge only fills one medium sized mountain bike tire, how on earth can it fill a motorcycle tire as claimed above!!!!????

As mentioned above, the BikeMaster kit does not indicate the size of its cartridges. However, they offer replacement cartridges that are 16g, so I think it's safe to assume the cartridges in the kit are 16g as well. The Pit Possee and Tusk state that their cartridges are 16g. However, I thought the better test would be to emulate the 4 cartridge BikeMaster kit.

So I gathered up 4, 16g cartridges (same as BikeMaster) and put them to the test on one of my motorcycle tires. We offer and I am using cartridges from the Air Kiss Kit made by Planet Bike. The kit cost about $15 and spare cartridges are anywhere from $10-25 for 3-packs depending on size. The air valves may look different, but they do the same thing...serve as a conduit for the air from the cartridge to the tire/tube.

I had four tires (from two motorcycles) to select to test the cartridges, and I picked the rear tire on my 2015 Kawasaki Versys 1000 LT. It's the biggest tire of the four at 180-55-17, it's tubeless and the spec pressure is 42 psi.

The first thing to take note of is the orange pad on the Air Kiss Cartridge. When the Co2 is discharged from the cartridge, it discharges so fast that the physical cartridge freezes. I'll show a photo of one all frosted after discharge later. I've heard some suggest that it gets so cold that it can burn bare skin. Maybe so, but the pad is a good feature and wearing gloves is a good idea.

Also, I note that the BikeMaster Kit doesn't include a cartridge pad such as the Air Kiss's, but the Tusk does.

The way the device works is the valve is screwed tightly onto the cartridge. Then the inflator valve is slid onto the valve stem and the  locking lever is raised. Finally, the cartridge is discharged by sliding the barrel of the inflator valve backward. The photo below shows the track that the valve barrel slides along. With that there's a wooosh, then it takes about 8-10 seconds for the air to stop flowing. Keep in mind that the Co2 is in liquid state in the cartridge and turns to gas in the atmosphere (or at a very high ambient temperature). When discharging into the tire/tube it may sound like the gas stopped flowing but it will take all of those 10 seconds to empty the cartridge.

You don't have to worry about the Air Kiss popping off. The lever locks it pretty well in place on the valve stem.

So, how much air did cartridge number one discharge in terms of PSI? 5 psi

Cartridge number two? 6 psi

Cartridge number 3? 5 psi

Cartridge number 4? 6 psi (note the frosted cartridges)

And the official results are:
  • Grams per cartridge = 16g
  • Average PSI per cartridge = 5.5 psi
  • Total grams/4 cartridges = 64g
  • Total PSI/4 cartridges = 22 psi
That would seem to at least confirm my suspicions that the Pit Posse and Tusk claims that one or one and a half cartridges will fill a rear motorcycle tire were a little ... uh ... let's say, exaggerated.

On the contrary, if 64 grams of Co2 produced 22 pounds of pressure in an "average" motorcycle tire, it would require 122 grams to inflate the tire to the spec 42 psi. That would mean 8-16g cartridges (actual calc is 7.6), 10-12g cartridges or 5-25g cartridges.

Another way to look at this, based on the test case is:
  • Each 12g cartridge will contribute 4.1 pounds to total psi
  • Each 16g cartridge will contribute 5.5 pounds to total psi
  • Each 25g cartridge will contribute 8.6 pounds to total psi

Okay, back to the original question, which was along the lines of...

"Are Co2 cartridges useful as motorcycle tire repair accessories?"

Here's my personal opinion. Used in an emergency kit that includes at least 4 cartridges, such as the BikeMaster Kit, I think the answer is probably yes. Those cartridges won't fill the tire to spec, but if the tire gets properly plugged or the tube is properly patched, 22 pounds of pressure is probably enough to get the motorcyclist to a filling station where he or she could deploy four quarters and air up your tires to the proper pressures. Adding more cartridges (or larger cartridges) to the kit is probably better; they certainly don't weigh much or take up much room. Use the per/cartridge psi information above to figure out how many cartridges you'd need to put you in your comfort range.

Now, here are some downsides that come to mind.

1--If you didn't get the tire properly plugged or the tube properly patched, you'll have expended your air supply when you have to go back and fix 'em. Both tire plugging and tube patching are kind of hit or miss processes. I don't think it's a great idea to assume it'll get done right the first time.

2--Similar to above, what if your riding buddy gets a flat and you fix it with your air cartridges? Seriously, how many bikers prepare for flat tires? 10-20 percent, less? Your buddy's tire is fixed; your air is gone.

3--The ambient temperature plays a role in how much Co2 is required for your application. The colder it is, the more Co2 would be needed. I did some calculations using our test info above. At 80 degrees Fahrenheit, 8 16g cartridges would be needed. At 50 degrees, 9 16g cartridges would be needed.

4--This is starting to get kind of expensive when you get into the number of cartridges necessary for motorcycles. The kits cost more than the $35 I paid for my Slime compressor that's already lasted half a decade and replacement cartridges are going to run minimally $10 for a three pack. You may see cheaper cartridges in the market place, but it's likely that they're the non-threaded type that are used in pellet guns. The air valves in the repair kits require "threaded" cartridges.

I'm sure there are many other pros and cons for using Co2 cartridges for motorcycles, but I'll bet they probably weigh themselves out. Having completed this little exercise, I would certainly support someone's use of a sufficient number of Co2 cartridges in their motorcycle road trip supply kit. On the other hand, I learned nothing that suggests I should pack away my Slime air compressor and move to cartridges on my motorcycles.


I've come across another motorcycle specific tire repair kit that has 2-45g cartridges. Genuine Innovations's Motorcycle Emergency Repair Kit runs $62 on Revzilla and provides 90 total grams of Co2. That's one 45g cartridge short from being able to fully inflate the rear tire of our test motorcycle. However, be warned, the larger the cartridge, the more expensive. The kit price is pretty high to begin with and two replacement 45g cartridges for the Genuine Innovations Kit run $35 on Revzilla!

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