knocking sound (or pinging) is very hard to describe.
if you can hear a metalic sound or if it sounds like "shaking a can of sand/marbles" or a rattling sound ...when u accelerate your engine, then your engine is knocking.
So my fingers and wallet were itchy and was tempted to try those space saver tyres (AKA Sotong Tyres). Purchase a pretty good one as per advice by the chop shop fella and man was I in for a surprised on the work...