How to Calculate the Volume of a Bicycle Tire
&
Pressure of Mountain Biking Tires
at Different Temperatures and CO2 Cartridge Sizes

Length = circumference
C = πd
C = 3.14159 x 26 in x 0.0254 m/in
C = 2.0747 m
Cross-sectional area (of a circle)
A = πr2
A = 3.14159 x ((2.1/2) in)2 x (0.0254 m/in)2
A = 3.14159 x 1.1025 x 0.00064516
A = 0.0022346 m2
Volume = Area x Length
V = A x C
V = 2.0747 x 0.0022346
V = 0.004636 m3

Moles of CO2
C, 12.0107 atomic mass units
O, 15.9994 amu
CO2 = 44.0095 g/mol
16 g cartridge
mol = 16 g x 44.0095 g/mol
mol = 0.3636 mol of CO2
25 g cartridge
mol = 25 g x 44.0095 g/mol
mol = 0.5681 g/mol

PV = nRT
P = (nRT)/V
16 g cartridge at 32° F
P = ( (0.3636 mol) (8.3145 (m3 Pa)/(mol K)) (273 K ) / 0.004636 m3
P = 178024.3 Pa
P = 178024.3 Pa x 0.0001450 psi/Pa
P = 25.8 psi
16 g cartridge at 85° F
P = ( (0.3636 mol) (8.3145 (m3 Pa)/(mol K)) (302.4 K ) / 0.004636 m3
P = 197196.1 Pa
P = 28.6 psi
25 g cartridge at 32° F
P = ( (0.5681 mol) (8.3145 (m3 Pa)/(mol K)) (273 K ) / 0.004636 m3
P = 278150.7 Pa
P = 278150.7 Pa x 0.0001450 psi/Pa
P = 40.3 psi
25 g cartridge at 85° F
P = ( (0.5681 mol) (8.3145 (m3 Pa)/(mol K)) (302.4 K ) / 0.004636 m3
P = 308105.4 Pa
P = 44.7 psi