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Motorcycle Tire Reviews
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Motorcycle Tire Air Pressure Conversions

Motorcycle Tire Air Pressure Conversions

Motorcycle tire performance is critical, and the air pressure of the tire is crucial.

Some owner’s manuals or other information lists motorcycle tire air pressures in various units of measurement.

This chart (below) converts pounds per square inch, or psi, into the SI unit.

The official SI unit for pressure is the Pascal (Pa = N/m2 = kg/ms2) or kiloPascal (kPa = 1000 Pa).

SI is an abbreviation for Système International d’Unitès, or the International System of Units.

MMore on Air Pressure

  • Explanation of the SI system from the National Institute of Standards and Technology (NIST) in the U.S.A. and other governmental standards organizations
  • The NIST publication SP811 is an excellent and detailed “guide to the SI, with a focus on usage and unit conversions”; it can be downloaded for free as a .pdf file and there are also other interesting links regarding measurement systems and their history on this page
  • The NIST Metric Style Guide (NISTLC 1137) is a brief description of metric units and how they should be used in print.

Formulas

Note: Pressure is any force which acts against a surface. The formula to define pressure is P = F/A where F is force and A is surface area.

Some motorcycle tire pressures are listed in psi (pounds-force/square inch), and others in kPa. Atmospheric pressure is approximately 100 kPa. The use of “kg/cm2” is a non-standard measurement.

Motorcycle Tire Air Pressure Conversions
kPa = psi * 6.89476
kg/cm2 = psi * 14.223343
bar = kg/cm2 * 0.980655
psi kPa kg/cm2 bar
20 138 1.4 1.4
21 145 1.5 1.4
22 152 1.5 1.5
23 159 1.6 1.6
24 165 1.7 1.7
25 172 1.8 1.7
25.5 176 1.8 1.8
26 179 1.8 1.8
26.5 183 1.9 1.8
27 186 1.9 1.9
27.5 190 1.9 1.9
28 193 2.0 1.9
28.5 197 2.0 2.0
29 200 2.0 2.0
29.5 203 2.1 2.0
30 207 2.1 2.1
30.5 210 2.1 2.1
31 214 2.2 2.1
31.5 217 2.2 2.2
32 221 2.2 2.2
32.5 224 2.3 2.2
33 228 2.3 2.3
33.5 231 2.4 2.3
34 234 2.4 2.3
34.5 238 2.4 2.4
35 241 2.5 2.4
35.5 245 2.5 2.4
36 248 2.5 2.5
36.5 252 2.6 2.5
37 255 2.6 2.6
37.5 259 2.6 2.6
38 262 2.7 2.6
38.5 265 2.7 2.7
39 269 2.7 2.7
39.5 272 2.8 2.7
40 276 2.8 2.8
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