Remember that the small contact between the BB's and the thermometer means you must wait a while to be sure the thermometer actually has equalled the temp of the BB's. Pour the BB's into the tube and cap the open end. Be sure to hold a hand over each end as you repeatedly invert the tube to let the BB's fall. Pour the BB's into a cup and again measure the temperature. The increase will be small so precision is required.
Auto brakes can get very hot.
Air resistance can vaporize meteors.