Infrared Thermometer

I got one from harbor freight a few years ago for about $30. seems to work well enough. I agree that what you are looking for is one brake, tire, or hub that is significantly different than the others. I was able to diagnose a brake that was not working as well as the other three on a trailer. Had one cold drum and the other three warm and within a few degrees of each other. Besides it's fun to point the thermometer at lots of other things, like the electric heater, extension cords that are overloaded, the dog's belly.....lots of fun uses. It's a neat educational tool also for kids and grandkids.