Schwalbe Marathon Plus vs. W5W Bulb Fragment: Standoff

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:

W5W fragment - on tire - side view
W5W fragment – on tire – side view

Pulling it out of the gash shows it’s the base of a W5W (or something similar) automotive bulb:

W5W fragment - on tire - front
W5W fragment – on tire – front

Which seems perfectly designed to cripple a bike tire:

W5W fragment - millimeter scale
W5W fragment – millimeter scale

The gash cuts all the way across the tire tread:

W5W fragment - tire gash
W5W fragment – tire gash

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 …