RossHelen editorial/Alamy
Why are the front wheels of my car always much dirtier than the rear ones?
Guy Cox
Sydney, Australia
I suppose Rob Janes [who posed this question] normally drives forwards, so the front wheels of his car encounter all the muck and slush on the road first and either accumulate it or swish it out of the way. We could plan a scientific experiment here: would he be willing to drive only in reverse for a month to see what happens to his wheels?
David Muir
Edinburgh, UK
The vast majority of particulate pollution from modern cars comes from friction…
