For around $200 you can buy a top-of-the-line infrared thermometer. When diagnosing brake drag problems, this tool can be indispensable.
The thermometers generally have a maximum accurate distance so they can’t be too far from the object being measured or the accuracy of the reading will be affected. Most manufacturers will list “angle of accuracy.”
Make sure to read the operating instructions for the unit being used. The biggest challenge in using one of these tools is what to do with the information. The information provided by these tools can be even more vague or elusive than hydraulic and clamping pressure readings. Here are some of the reasons why:
• No specifications provided;
• No way of knowing how much front-to-rear temperatures should vary;
• On side-to-side differences, it can be difficult to determine which reading is the problem; and
• Some side-to-side differences can be expected under normal brake operation.
Here are some pointers to follow when taking temperature measurements:
• Take the measurements close to the object being measured and as soon after the test drive as possible.
• Compare side-to-side readings. Look for symptoms of excessive heat such as bluing of the rotor. This will help determine if a wheel is running too hot or too cold.
• Excessive heat on one wheel can be caused by a wheel being overworked, a lack of release or an excessive side-to-side difference in rotor thickness.
• Don’t always condemn the high-side reading; it is possible that the low side isn’t working enough.
• Remember that excessive heat is a symptom of something else wrong in the system.
