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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 01-26-07, 03:31 PM   #1
Hermes 
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CO2 Canisters

I had a flat on my road bike this week and it was my first flat in 7 years (not much debris on the roads) and the first time I used a CO2 canister. Well, I am proficient at fixing a flat on the road with a pump but I was about as proficient as a gorilla using the CO2 canister. I carry two and immediately squandered the first one in my attempt to connect the cartridge to the valve system provided to control the air into the tire. It was high 40s outside and the cold CO2 cartridge, leaking connections and my fumbling left my fingers very cold and I did not have the tire on the back on the rim yet. I completed the fix and then used the second cartridge to get some inflation. Off I went but with very little pressure in my tire .

Lessons learned:

1. The cartridges get very cold upon discharge so use one’s glove to hold it to protect skin from potential leaking CO2 and cold cartridge.
2. Have at least two cartridges and I now carry three. One cartridge provided about 40 psia.
3. Practice once in controlled conditions.
4. All cyclists that went by offered assistance.
5. The CO2 that is now in the tire will leak out in a couple of days. After one returns, release the CO2 from the tire and re-inflate with air.

Question:

How many canisters does it take to inflate a tire on a tandem up to 120 psia?
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Old 01-26-07, 03:53 PM   #2
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I've been using CO2's for 10+ years and just recently went back to using full size frame pumps again. Just the thought of not running out of air on those long rides is worth the trouble of carrying a good pump. Twice last year I ran out of cartridges when I flatted multiple times during long rides.
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Old 01-26-07, 04:00 PM   #3
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1. Yep (I wear thin glove liners while changing the tire in cold weather)
2. I get about 95# out of a 16g cart in a 650C tire (that's my road bike; I carry a pump on my tandem)
3. Yep, though I've never wasted a cart yet after about 20 uses.
4. Most cyclists are nice people.
5. I pump my tires before every ride so don't care if the CO2 leaks out.

I changed a flat Wednesday in 23F weather and was glad to be using CO2. I was back on the bike in under 5 minutes which is a good thing in cold weather. The first thing I do when changing a flat when it's that cold is to put the cart in a warm place (use your imagination) to warm up while getting the tire ready.
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Old 01-26-07, 04:06 PM   #4
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Quote:
Originally Posted by The Fixer
I've been using CO2's for 10+ years and just recently went back to using full size frame pumps again. Just the thought of not running out of air on those long rides is worth the trouble of carrying a good pump. Twice last year I ran out of cartridges when I flatted multiple times during long rides.
Great point...Multiple flats are a reality and I was not happy with the amount of air pressure in the tire using the CO2.
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Old 01-26-07, 04:27 PM   #5
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Topeak Road Morph, aka "The Smug Pump" -- as in, "here, step aside everyone and quit screwin' around... use my Road Morph."



-Greg
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Old 01-26-07, 04:30 PM   #6
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A 12g cartridge will get you to about 80psi
A 16g cartridge will get you to about 130psi

To extend the range of the 80psi, one of the tricks is to also carry a frame pump and use it to fill the tire part way and then use the C02 to top off and eliminate the more difficult pumping job.

FWIW: I'm a frame pump guy; gotta love the unlimited supply of air.
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Old 01-26-07, 04:43 PM   #7
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We use the Topeak Mt. Morph (bit shorter/lighter than the road version).
Also carry one CO2, in case pump fails (have broken/busted pumps, but never a Topeak).
Free air is hard to beat! 100 pump strokes gets us 100 lbs in 700x25 tandem rire. 120 strokes/120lbs.
No flats in 7 years? Yipes you either must not ride much or have great karma!
On a cold day CO2 discharge will not warm you . . . but 100 pump strokes will!
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Old 01-26-07, 04:59 PM   #8
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Quote:
Originally Posted by TandemGeek
A 12g cartridge will get you to about 80psi
A 16g cartridge will get you to about 130psi

To extend the range of the 80psi, one of the tricks is to also carry a frame pump and use it to fill the tire part way and then use the C02 to top off and eliminate the more difficult pumping job.

FWIW: I'm a frame pump guy; gotta love the unlimited supply of air.
Thanks T'Geek. On the tandem, I have both pump and canister. When I switch to my roadie mode, I go minimalist. However, until last week, I did not use the canister in practice and after my result; I was not sure how much pressure in practice one could achieve. There is a simultaneous thread in general cycling on CO2 canisters with similar experiences to mine. I have several frame pumps in the garage from which to select and accumulating recommendations from this thread if I want one. However, I like the pump up and top off story for the tandem.
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Old 01-26-07, 07:32 PM   #9
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Quote:
Originally Posted by gregm
Topeak Road Morph, aka "The Smug Pump" -- as in, "here, step aside everyone and quit screwin' around... use my Road Morph."



-Greg
Thanks for the tip.

I see that there is also a Road Morph G with a pressure gauge. Does anyone reccommend this as a viable primary pump to pack with an S&S coupled tandem?
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Old 01-26-07, 09:43 PM   #10
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Quote:
Originally Posted by TandemGeek
A 12g cartridge will get you to about 80psi
A 16g cartridge will get you to about 130psi
Wow, I must be doing something wrong. You're getting more in a 700C than I am in a 650. My cart supplier must be cheating.
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Old 01-26-07, 11:25 PM   #11
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You can use the Topeak Morphs as a primary pump; no need to haul around a big floorpump on trips.
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Old 01-27-07, 08:08 AM   #12
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Quote:
Originally Posted by Trsnrtr
Wow, I must be doing something wrong. You're getting more in a 700C than I am in a 650. My cart supplier must be cheating.
Perhaps it's faulty memory on my part, it's possible that the 16g get you about 100-120psi and the 25g the >135psi (really meant for MTBs). However, as best as I can recall, these are something like nominal performance on a 700x23 for a clean-fill. A "little leak" during the fill process seriously reduces their effectiveness.

Again, afer fiddling around with them for one season I elected not to use them. If I was racing and had to fix my own equipment on the road or trail, that would be a different story.

For those "sport" and "recreational" riders who want to use the C02 carts, I still suggest carrying a pump and using it to get the tire filled enough to get the bead properly seated (i.e., enough to verify the tube isn't pinched) and to make sure the stem is firmly seated before using the cartridge. These two steps usually produce the best results with a C02 cart and eliminate the need for a "do-over" or the use of a second cart to get you home.

FWIW: ...and please don't challenge me on or ask me to dig up science behind this last item, as already mentioned by the OP the word on the street is after using a C02 inflator to get you back on your way, once you have access to a floor pump you'll want to deflate the tire and then reinflate it with the pump to mitigate C02's faster bleed down times vs. the junk we breathe. I read what the chemists have to say on this and it makes sense. At the same time, I can't confirm the bleed down effect because I top off tires every time I ride and, again, only used them on my personal bikes for one season.

Last edited by TandemGeek; 01-27-07 at 11:12 AM.
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Old 01-27-07, 08:33 AM   #13
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I agree that the road morph is one fine pump. Seems like in the long run it works, unlike most others. The kids have the one with the built in gauge and though its not super accurate its close enough. The built in gauge is a plus if you have a hard time judging how much pressure in the tire.
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Old 01-27-07, 08:49 AM   #14
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Quote:
Originally Posted by lordoftherings
Lessons learned:

1. The cartridges get very cold upon discharge so use one’s glove to hold it to protect skin from potential leaking CO2 and cold cartridge.
Good physics here. The sudden reduction of pressure reduces the temperature. This is the basis of (most) refrigerators. You can also notice frost developing on the neck of a CO2 fire extinguisher when it is being used.

Glenn
Physics Prof.
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Old 01-27-07, 09:09 AM   #15
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We also carry CO2 carts and frame pump and follow tandemgeek's system. In central California we get one flat a week in the late summer and fall (puncture vine) and one flat a month the rest of the year (man-made debris) in average. We like having the two systems at hand as backups and complements to each other. We are hooked on CO2 because we are usually in groups and do not want to keep the group waiting unnecesarily. Unless we could carry an endless supply of CO2 carts, which we can't, we try not to ride without the frame pump... our record is five flats in a 60 mile outing.
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Old 01-27-07, 09:11 AM   #16
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Quote:
Originally Posted by TandemGeek
FWIW: ...and please don't challenge me on or ask me to dig up science behind this last item, as already mentioned by the OP the word on the street is after using a C02 inflator to get you back on your way, once you have access to a floor pump you'll want to deflate the tire and then reinflate it with the pump to mitigate C02's faster bleed down times vs. the junk we breathe. I read what the chemists have to say on this and it makes sense. At the same time, I can't confirm the bleed down effect because I top off tires every time I ride and, again, only used them on my personal bikes for one season.
I've never experienced this issue since I haven't used CO2 carts, but I believe the permeation rate of CO2 through polyisobutylene (aka butyl rubber used in inner tubes) is more than 10x higher than for air (mostly N2 and O2). So the pressure drop over time is certainly going to be quicker with CO2. You could just keep topping off with your hand pump over a few days (week(s)?) until the CO2 concentration is reduced significantly or you could be more efficient and get it over with by bleeding down the tire and refilling.
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Old 01-27-07, 09:54 AM   #17
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We carry both on the tandem, 2 co2 cylinders for ease of use, and a frame pump for backup. On my singles I usually go with 2 co2's, with a cell phone backup. I get about 110 lbs on a good fill, 80 on a screw up.
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Old 01-27-07, 10:04 AM   #18
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We've got the little Sigma that converts to a mini floor pump, complete with gauge. I used Co2 once on my single, and found that I prefer to use a pump instead.
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