I believe it's from the olden days of buying an automobile - people kicked the tyres to see if a wheel was wobbly or had a shot bearing or whatever (I mean, the wheels were basically re-purposed horse cart wheels at the very beginning).
I thought it was from people who didn't know anything about cars, so would kick the tyres to see if they were pumped up. Thus making it look like they knew what they were looking for.
I believe it's from the olden days of buying an automobile - people kicked the tyres to see if a wheel was wobbly or had a shot bearing or whatever (I mean, the wheels were basically re-purposed horse cart wheels at the very beginning).