Using Ultrasonic Thickness Gauges for Measuring Drum Brakes

Maintaining the appropriate thickness of brake drums on your commercial vehicles not only keeps them performing optimally, but can help prevent serious consequences while driving, like shattering or failure to stop. To protect the safety of drivers, Ontario adopted a new standard for commercial transportation requiring brake drum thickness measurements be made and recorded.

Ultrasonic Thickness GaugeOne the most effective and accurate devices to measure drum material thickness is an ultrasonic thickness gauge, like the REED TM-8811, ideal for technicians to meet the new automotive inspection requirements. Ultrasonic thickness gauges don't require access to both sides of the sample, can be engineered to cope with coatings, linings, etc., accurate (0.1 mm and less), can be easily deployed and does not require laboratory conditions. Previously, the measurement and recording of drum brake linings for commercial motor vehicles - trucks, trailers, buses, accessible vehicles and school purpose vehicles - were not required in accordance with Ontario inspection standards. To ensure matters dealing with licensing, registration and control of motor vehicle transportation and highway safety, including the thickness level of brake drums, critical to motor vehicle safety, Ontario adopted the National Safety Code Standard, effective July 1, 2011. The National Standard outlines these inspection criteria for Safety Standard Certificates, Annual Inspections and Semi-annual inspections, for hydraulic brake systems and air brakes:

Visual inspection of the following hydraulic brake components/systems:

  • Drum Brakes - requires drum removal in almost all cases; drums to be measured and an operational check performed.
  • Disc Brakes - requires rotor thickness to be measured and an operational check performed.

Visual inspection of the following air brakes components/systems:

  • Drum Brakes - requires lining thickness measurements to be taken and recorded.
  • Disc Brakes - requires rotor and pad thickness to be measured and recorded.

Ultrasonic thickness gauges determine drum material thickness by measuring how long it takes sound to travel from the transducer through the material to the back end of a part, and then measures the time which the reflection takes to get back to the transducer. The ultrasonic thickness gauge then calculates the data based on the speed of the sound through the tested material and determines how thick the metal is.

Unlike traditional drum micrometers and similar tools, the non-destructive technology of the TM-8811, features impressive accuracy (0.1 mm and less,) and the fact that it does not require the inspector to access both sides of the sample, makes it a single-solution for measuring and recording drum brake linings. Other Reed TM-8811 Ultrasonic Thickness Gauge product features include:

  • Broad band receiving sensitivity means the meter can read probes of different frequencies
  • 4-digit, 25/64 inches high LCD readout
  • Automatic material calibration
  • Selectable metric or imperial
  • Includes hard carrying case and batteries
  • Display sounds velocity at the touch of a button
  • Range: 0.06 to 8"/1.5 to 200mm
  • Resolution: 0.001"/0.1mm
  • Accuracy: +/- 0.5 percent + 0.2"/0.1mm
  • Velocity Range: 500 to 9000 m/s
  • Power Supply: 4 x 1.5V "AA" batteries
  • Measures 6-19/64" length by 2-11/16" width by 1-1/4" depth.

Looking for a REED distributor in Toronto Great Area? As a Reed Instruments distributor, we sell a wide variety of Reed Ultrasonic Thickness Gauges in Canada, from our Brampton (Toronto area) warehouse. Buy this most effective and accurate REED TM-8811 device from us.

For the complete inspection requirements for commercial motor vehicles from the Ministry of Transportation, visit

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