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.