One of the A riders in the club posted on the Yahoo group that he was making the move to CO2 cartridges, after many years of resisting them. That started online discussions that took two separate tracks.
Another member asked, “How many pounds of pressure does a 12 gram cartridge impart to a 700×23 tire? I use 16g cans and still have trouble getting home with the optimum 92-94 lbs onboard.”
The Internet is a wonderful thing. It doesn’t take long before answers start rolling in. Multiple answers.
“I’ve never checked the actual pressure,” answered a fast rider, “but my 23′s are quite firm after using a 12 gm cartridge. I just did a bit of research and it appears that you get about 100 psi in a 23mm tire from a 12 gm cartridge and about 125 from a 16 gm.”
But that doesn’t allow for individual differences. The fellow who posted that probably doesn’t weight more than 130 pounds soaking wet. The original poster followed up:
“Am I the only one who rides 25 mm tires? What did your research say about the pressures in the larger road tire?”
Cripes. We haven’t answered the cartridge size question yet, and now we’re introducing tire size variations? It’s gonna get confusing.
“I ride 25s too,” chimed in another member, “and am somewhat heaver than Steve so you probably will not be surprised to hear that I only roll with the 16s on the road bike. However, I also put some Gatorskins on the wheels so I don’t get flats very often any longer [although I just jinxed it and am sure to get a flat on my next ride] so the extra cheese spent on the threaded 16 gram cartridges isn’t a big deal. If you use less than 6 of these a year, it’s not a major expense.” But he also had a practical suggestion.
“Go buy a 12 gram and a 16 gram cartridge. Let all of the air out of your rear tire, fill it up with the 12 gram cartridge, and go for a ride. Repeat with the 16 gram. Which did you like better?”
I imagined pffffft! sounds coming from garages all over the neighborhood as cyclists took him up on that idea.
Then, of course, there’s that complication you get with CO2:
“Bear in mind that CO2 bleeds out of a tire much faster than pumped air,” wrote the 130-pounder, “so if you fix the flat in the early part of a three-hour ride, you will find a lower pressure when you get home. This is why, after fixing a flat on the road with CO2, I always deflate the tire and refill it with a pump at home. However, unless it gets down in the low 80 lbs range, you shouldn’t have any problems short of a pinch flat if you hit a big pothole or rock.”
Okay, this is all good information. But one member had a great idea: Go right to the source. The Genuine Innovations website has a link to an inflation chart.
“Unfortunately there isn’t a measure for the 25mm tire,” said the guy who suggested experimenting. “But there is one for 23 and 28. You should be right in the middle. It looks like a 12gm will get you 90psi in the 23mm tire and 62psi in the 28mm tire or about 80psi in the 25mm. If you want a higher pressure, go with the 16.”
What was the second discussion track? Cost, of course.
The original poster wrote: “If you buy cartridges from a bike shop they can be pretty expensive. I just checked online and it appears that you can get them reasonably cheap if you get a bunch of them. For example you can get a box of 50 16 gram non-threaded cartidges for $50 including shipping. And different prices for different amounts. but 50 for $50 seems about the best.”
Another replied, “Buy a box of 12 gram cartridges at Walmart in the BB/paintball gun section. 15 for $7.97.”
“+1 on that recommendation,” said a third. ”I buy mine in bulk from a discount sporting goods store. The only thing is that these do not have the threads to screw into some of the smaller nozzles. I had to use it this weekend and a single Crossmark CO2 cartridge inflated my tire in one shot.”
Well, that was settled pretty quickly. Looks like a bunch of my club pals are headed for Wal-Mart to get their CO2. But one of the previous commenters signed off with some wise advice:
“Even though I’ve had good luck with cartridges, I still have a frame pump attached to my bike just in case Mr. Murphy is drafting.”