Joined: Oct 2008
Posts: 4,423
Likes: 4
From: wessex
Bikes: breezer venturi - red novo bosberg - red, pedal force cg1 - red, neuvation f-100 - da, devinci phantom - xt, miele piste - miche/campy, bianchi reparto corse sbx, concorde squadra tsx - da, miele team issue sl - ultegra
a puncture doesn't indicate that the tire is worn out necessarily. it means that it is either under inflated or you ran over something sharp and poked a hole in your inner tube.
a sidewall cut, compromised casing from a puncture, or the casing showing through the threads indicates time for replacement.
btw, preventatively replacing your tires won't ensure you flat-free riding. but proper inflation, checking the tires for embedded debris and such can help reduce the risk.