Am I running over urine on the road?

[DeadmanDave]

I check my tires for weird smells, and if anything smells off, I take it to the car wash to clean it off. Lately, I've been checking them before heading home from work and finding nothing, and then often after arriving home, finding a urine-like smell on one or two, and then rushing it to the car wash immediately to get it off. Am I actually running over urine or maybe something else on the road?

 

[Ftttu]

Dogs are known to do their business on tires, among other objects.

 

[DeadmanDave]

Apparently, dogs aren't sneaking up to my car. A close friend of mine and my parents' said that I'm going to run over all kinds of stuff and that routinely smelling the tires is going to drive me crazy.