Randochap said:My tyres are usually retired long before the tread has actually worn through, due to nicks and cuts from road detritus.
I do keep cheaper/heavier winter tyres for my bikes though (and a winter bike for that matter) and repair bigger cuts with Super Glue.
I find this only works sucessfully if the tyre is cleaned thoroughly and washed down with something that evaporates completely, ie Ethanol Absolute.

Scwalbe city jet on my old rockhopper, with slime inners, 3500 mls, 1 "p", still wear left!