Procedure and Equipment for Measuring Tire Air Pressure

We recently received a DVER that placed our vehicle out-of-service for a flat tire. The violation noted that the tire had 53 psi pressure (max 110 psi). The CVSA Out-of-Service Criteria considers a tire that has 50% or less than the maximum inflation pressure marked on the sidewall to be out-of-service. In February of 2002 an Issue Request for Action was submitted to the CVSA Vehicle Committee, by Sgt. Klausner, Houston TXPD. The question asked was should a tire gauged at 1 psi below the recommended level be placed OOS or should there be a percentage value followed? The response from the committee is as follows: “It was discussed that accurately checking tire inflation is complex and cannot be one without an accurate gauge. Tire inflation values are set on cold-tire conditions. In spite of the complexity of accurately determining tire pressure, flat is flat. When the tire is coming off the rim, smoking hot, or caves in when pushed, the tire is flat and an OOS condition exists. Until such time that there is a method of measuring accurate tire pressure, tire pressure gauges should not be used unless they are intended to be used to confirm that a tire is definitely flat”. There have been no updates on this issue since this request was processed.

CVSA’s Operational Policy 15 gives regulatory guidance that basically states because of the variables in measuring low inflation pressure of tires, 393.75(h) should not be written for an underinflated tire. CVSA’s OOS criteria (Section 11 a. (7) & b. (1)), flat tires, would be in conflict with Ops Policy 15, because it requires measuring low tire inflation. The nonprofit group, Consumers Reports, found when testing 14 different types tire-pressure gauges that accuracy was affected by temperature of the device itself and when dropped to the flood from heights of only 30 inches. Although the NAS Level I Inspection Procedures list "check for proper inflation" of tires, there is no standard on the procedure or equipment used when determining tire air pressure. In the incident mentioned above, our carrier was placed out of service at roadside per the CVSA OOS criteria and received 30- points on the CSA SMS for 3 pounds of air pressure. This measurement of the tire air pressure was performed without uniformity of a standard in the procedure or equipment used.

Change the CVSA OOS criteria to reflect the decision made by the Vehicle Committee reference Issue No. 02-001-VEH by removing the statement, "or has fifty (50) percent or less of the maximum inflation pressure marked on the tire sidewall" until such time as a valid method (procedure and equipment used) of measuring tire air pressure can be provided.