Tyre Pressure with CO2

buckmulligan
buckmulligan Posts: 1,031
edited February 2013 in Road general
Had my first puncture of 2013 at the weekend and (rather sadly) I was quite happy since I used my emergency CO2 pump for the first time :oops: Its a Lezyne Trigger Drive with a 16g cartridge and got my 23mm tyres up to a decent enough pressure, rode for another 40-odd miles without any concerns or strange feelings from the front end. Great piece of kit, so much easier than heaving away with a mini pump for 5 mins in the freezing cold :D

Checked it this morning though and it's pretty flat (20-40psi maybe) :? Don't think it's a slow puncture, I found and removed a great big thorn from the tyre which obviously caused the first flat. Just wondering what kind of pressure it would have gotten it up to at the roadside? I know manufacturers claim 90+ PSI, but is this like their rather optimistic component weights? And does CO2 leak out of the tubes faster than normal air? Thanks.

Comments

  • ShutUpLegs
    ShutUpLegs Posts: 3,522
    90 psi
  • Have a read of this thread for a discussion on the effects of inflating tubes with co2

    viewtopic.php?f=40012&t=12798742
  • Dave_P1
    Dave_P1 Posts: 565
    If you've lost that much pressure over night then I expect you have a slow puncture or fault valve. I would remove the tube and double check before heading out again.
  • I've used a co2 a number of times.

    And I checked with a track pump when I got home, pressure was just over 110psi. (This is using a hand pump to get a little air in to help seat the tube) I've heard some stories where people don't seat the tube correctly and because of how fast the tube inflates under co2 it causes pinch flats.
    “If you worried about falling off the bike, you’d never get on.”

    @mattbeedham
  • Scrumple
    Scrumple Posts: 2,665
    I've wasted a few cartridges with the valve freezing up and the tyre going flat instantly!

    I'd check your valve, and make sure it is screwed shut. Or replace the tube.
  • diplodicus wrote:
    Have a read of this thread for a discussion on the effects of inflating tubes with co2

    viewtopic.php?f=40012&t=12798742


    CO2 leaking faster than air sounds unlikely to me. CO2 has a molecular diameter of 3.87E10^-10, nitrogen molecules, the main component of air are 2.40E10^-10 (O2 is even smaller) so CO2, being larger, is less likely to leak from an inner tube.
  • sungod
    sungod Posts: 16,522
    it's not molecule size that counts, co2 is attracted to the butyl molecules, in effect it dissolves into the butyl, permeating it and evaporating the other side

    n2 and o2 do not behave this way, so they stay put longer

    according to this...

    http://ve4ep.com/a/20june/ScienceDirect ... atings.pdf

    co2 will escape butyl rubber about four times faster than o2, and 16 times faster than n2
    my bike - faster than god's and twice as shiny
  • Strith
    Strith Posts: 541
    ^this.
    I used to use co2 and yeah the pressure would drop a fair bit by the next day. I check my tyres everyday anyway so it was never an issue for me.
  • sungod wrote:
    it's not molecule size that counts, co2 is attracted to the butyl molecules, in effect it dissolves into the butyl, permeating it and evaporating the other side

    n2 and o2 do not behave this way, so they stay put longer

    according to this...

    http://ve4ep.com/a/20june/ScienceDirect ... atings.pdf

    co2 will escape butyl rubber about four times faster than o2, and 16 times faster than n2

    Ok, teaches me not to be a smart r's
  • Gizmodo
    Gizmodo Posts: 1,928
    I agree, not sure about the science, but from experience of using CO2 in the past, the next day it's almost all gone. When you get home, or before your next ride, you need to empty out the CO2 and replace with air from a track pump.

    I had to use my CO2 again today, if I remember I'll post here what pressure I have tomorrow.
  • Gizmodo wrote:
    I agree, not sure about the science, but from experience of using CO2 in the past, the next day it's almost all gone. When you get home, or before your next ride, you need to empty out the CO2 and replace with air from a track pump.

    I had to use my CO2 again today, if I remember I'll post here what pressure I have tomorrow.

    +1 always been my experience too.
  • priory
    priory Posts: 743
    I love co2 cylinders but never fail to take a pump, and usually I fill the tyre with the pump until some effort is needed then harden it with co2. rock hard instantly no effort. But yes, it needs topping up next day.
    take a pump in case you get more problems than you have cylinders, which will definitely happen if you don't.
    Raleigh Eclipse, , Dahon Jetstream XP, Raleigh Banana, Dawes super galaxy, Raleigh Clubman

    http://s189.photobucket.com/albums/z122 ... =slideshow