A clicking sound from the rear of the bike suggested something was amiss as I rolled up the driveway after a recent ride. Spinning the rear tire produced this alarming sight:
Pulling it out of the gash shows it’s the base of a W5W (or something similar) automotive bulb:
Which seems perfectly designed to cripple a bike tire:
The gash cuts all the way across the tire tread:
The blue stuff is Schwalbe’s rubber / latex / plastic SmartGuard layer, all 5 mm of it hard at work separating the glass from the inner tube.
I cleaned the wound, filled it with silicone rubber, topped it with some duct tape, and it’s still holding air after a 13 mile ride. I think the gash cut through the rubber tread and SmartGuard layer, but didn’t affect the cords in the tire carcass, so keeping further road debris out of the gash should let the tire wear out more-or-less normally.
Putting duct tape on the tread will certainly help …