No upper limit i belive on cars for the very reason said above, agree on bikes...
But breach of the piece is a possibility, but this has to be a constant.. 5zigens are loud at 4k / under load but under that they are pretty quiet...
As he had no way of proving your speed or have anything on your dec limit, just smile and nod....
PITA though... Bet there was someone being burgled or knived when he spent 10 mins dealing with you...
BTW, you know that 19" add an extra 5ish MPH to your speed.... or so my GPS says...