How many 16g CO₂ Cartridges does it take to inflate a Honda CT125 tyre?

I was putting together my off road repair kit and wanted to know how many 16g CO₂ Cartridges to take. So made a video of how many it takes to inflate the tyres on a Honda Trail/Hunter cub CT125. I thought others might find it useful.

Thanks for testing and sharing the data. Good to know for anyone considering carrying cartridges, especially the note about co2 leaking faster over time.

I just bought a co2 kit. Good to know.

dmonkey said:

Thanks for testing and sharing the data. Good to know for anyone considering carrying cartridges, especially the note about co2 leaking faster over time.

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The tyre lost 3 psi over 24 hrs which is good to know but I still let the pressure out and filled with air.

Another good data point to know! Was that with the stock inner tubes? I ask because the info I found on those is that they're a mix of both butyl (synthetic) and latex (natural) rubber - where butyl rubber is known for being less porous than latex so I would expect the stock tubes to hold overnight better than many of the aftermarket options that prioritize puncture resistance instead.

dmonkey said:

Another good data point to know! Was that with the stock inner tubes? I ask because the info I found on those is that they're a mix of both butyl (synthetic) and latex (natural) rubber - where butyl rubber is known for being less porous than latex so I would expect the stock tubes to hold overnight better than many of the aftermarket options that prioritize puncture resistance instead.

Click to expand...

Stock inner tubes, the bike had 10Klm when I got it and I've only done 270Klm so far - weather and all that

Instinctively, based on MTB tires (because these are the same width as MTB tires but a smaller diameter), I would have said "2, maybe a shade more, but 2 for what I run my tires at".

From a math perspective, I'd have guessed 2 as well. PV=nRT, the ideal gas law. nRT is constant if comparing two tires at the same temperature, inflated from 2 CO2 cartridges. P is lower for 29er tires by 60%, V is lower for CT125 by 60%, so those two cancel each other out. They sell 38g threaded CO2 cartridges to get those large volume tires up to ~20 psi, or tell you to use 2 and a pump.

Fun fact: 3.75" tires were the maximum size a bicycle tire could be made at before Surly Bicycles (subsidiary of QBP) went to Taiwan and reconfigured the tire manufacturing machines so they could produce fat bikes. Now they make up to 4.8" tires.

The 38gm cylinders are mostly designed for and used in life jackets. In the US these have a 3/8 UNF thread but in Europe they are usually 1/2” UNF - be aware if ordering

I wired a 12v pigtail to my battery and carry a pump?