Commuting - G.I. CO2 recommendation chart even close?

I had an opportunity today to use my Genuine Innovations Ultraflate Plus for the first time since I bought it a year and a half ago. It was my first flat since getting it though I'm not sure how I've managed the streak of fortune. It worked like a champ and I didn't have any issues except for (sort of) one thing. When I got home, I gave my bike the once-over and put a new tube and 12 gram cartridge back in the seat pack. Just for a wag, I checked the pressure on the tire I repaired and was quite suprised to see that it was at 60 psi. I run 700C x 25 front and back.

According to the G.I. website, a 12 gram cartridge will inflate a "27 inch road tire to 90 psi". 90 psi is about where I keep tire pressure so it seemed reasonable that this was the cartridge size of choice for my seat pack. Just to make sure I hadn't used the inflator incorrectly, I repeated the process in my garage, with the same results.

While I realize calling something a "27 inch road tire" is pretty broad and covers a lot of possible sizes, I didn't think a reasonably equivilant 700C x 25 was so much removed in size that I only got 2/3 the "rated" fill.

Where did I screw up my math?

It worked like a champ and I didn't have any issues except for (sort of) one thing. When I got home, I checked the pressure on the tire I repaired and was quite surprised to see that it was at 60 psi. I run 700C x 25 front and back.

Well, now you know! :thumb:

You may want to consider adding a presta/Schrader adapter to your patch kit so you can top the flatted wheel off next time.

60 PSI will get you home, won't it? I would be extra careful to avoid potholes and such to avoid pinch flats, but I doubt even that would be an issue.

I look at CO2 inflators as emergency tools, and thus rarely used. I don't expect foot-pump pressures, and adjust the post-flat part of my trip accordingly.

Unfortunately, I've had a bit of experience with that this year!

For me, a 12 gram cartridge will inflate a 7000 x 25 tire sufficiently to finish a ride, but not to the 110-120 psi that I normally run.

The other thing about CO2 is that it tends to leak or leach out of the tube faster than air does, so what may have felt like sufficient right after you used it may not seem nearly so by the time you get home. I think I read somewhere that the CO2 molecules are smaller than O2, but don't quote me on that.....

I have a frame pump, works with multiple flats and gets good pressure.


and I have probably now guaranteed I will use it on the way home today :)

CO2 molecules are smaller than O2Except you fill your tires with air, of which O2 is only 20% (almost everything else is Nitrogen).