TWI

‘Damn, my brand new bicycle tire is already damaged’.
‘That’s a bummer, mate. Did you ride through glass or metal shrapnel?’
‘Nope, I think it was already damaged before I got the bike... it just small damage though’.
‘Ah, are there two small dot-like indents?’
‘Yeah, how do you know?’
‘Cause I’m a part-time cycle-mechanic and those things are your thread wear indicators. If you DON’T see them anymore, then you worry...:’

Picture for reference.