Tire Inflation with C02 in the cold...

[Dirt]

I re-discovered something interesting last night. When it is cold out, CO2 cartridges don't put near as much pressure into your tires. I kept thinking I had a slow leak and it was just because I had changed a flat and used CO2 to fill the tire instead of a pump.

Note to self, carry a pump in the winter.

Peter

[Squirrel Girl]

Works for *you* but now that I'm tubeless (no, I didn't say *clueless* -- which is probably more accurate), I don't think a pump will work for me.

However, as I scientist, I'm intrigued by your statement. We know that automobile tires will expand during driving on a hot summer day. And I think that I once had a tube pop when I'd overfilled it on a cold morning, then rode it in the warm afternoon. Or maybe it went kerpow without being ridden.

Anyway, now I'm thinking about the ideal gas law, PV=nRT and all that. Does anyone know the volume of a tire? I imagine somewhere I could look this up or actually even calculate it with my long-forgotten geometry. But if someone knew off-hand, that would make it easier.

Barbara

[crashmore]

If you're running tubleless you should still be carrying tubes and a pump in case you get a flat. It's not practical to patch and reseat a tubless tire out on the trail. You should also consider running a cup of Stans in each tubless tire as a backup. That saved me a couple times.

On a side note I run tubeless tires on my Scalpel and regular tubes on my Blur. I thought I'd miss the tubeless but I'm really not. Actually with the standard setup being lighter I'm starting to consider staying with a standard setup when I upgrade the wheels on the Blur.

[Dirt]

On a side note I run tubeless tires on my Scalpel and regular tubes on my Blur. I thought I'd miss the tubeless but I'm really not. Actually with the standard setup being lighter I'm starting to consider staying with a standard setup when I upgrade the wheels on the Blur.

I've ridden a few bikes with tubeless and I don't like it that much.


Anyway, now I'm thinking about the ideal gas law, PERVERT and all that.
Barbara


I'm not familiar with that law.

Peter

[Squirrel Girl]

OK, here it is. I got a co-worker to give me a formula for determining the volume of a tire.

Here are my assumptions:
26 x 2.1 inch tire
25 g CO2 cartridge
CO2 acts as an ideal gas

At 85 degrees, the tire will be at 44.7 psi.
At 32 degrees, the tire will be at 40.4 psi.

Isn't science fun? :)

[Dirt]

CO2 acts as an ideal gas

I think there's a song in there somewhere. :)



Isn't science fun? :)

Actually it is. :) Lets just say that I really felt the difference in pressure... enough that I'm carrying a pump these days.

Thanks for the info.

Peter

[mark w]

Pressure, schmessure

get yourself some big heavy tires and you need not worry about such things. :D I much prefer volume to high tire pressure in the pursuit of flat prevention.

I cant remember the last time I ran over 35 psi in any of my XC bikes. I have been having mixed feelings about tubeless lately. I seem to be getting far more sidewall cuts up here than I ever did in Blacksburg. Not the big, ride-ending cuts that we all fear, just little ones that are far enough up to give the goop in my tires the slip. I've had much more success with tubeless on my DH bike as the tires are thicker and have even more volume.

[Dirt]

Very true, Mark.

I'm a fair amount heavier than you and I run 38 psi in my XC tires.

The original problem was that I didn't get near that much from my CO2 cartridge. The back tire was flopping when I'd go through the corners.

Peter

[TrailVictim]

I run Panaracer XC Pro 2.1 UST with a squirt of Stan's and I haven't had a flat all year. We'll if you count the lame curb hop I did that blew out my tire and mashed a nice flat spot on my Crossmax, I guess you could chalk that up as a flat.

[Dirt]

I think part of the reason that the CO2 thang was such a revelation to me is that I so rarely get flats. I'm always helping other people out with theirs, but they always turn down my offer of CO2. I guess that makes them the smart ones. ;)

This is my second flat this year. That is more than twice my annual average.

Now I jynxed myself. I'm sure I'll have flats in every ride from now till January.

Oh well. I gotta run find a live chicken to sacrifice.

Peter