Hey Dave. From what the pic seems focused on - that is a puncture rather than a crack. No steel belts, baby! You wouldn't want that!
The Conti GP 4000s is one of my fave tires. I don't discard them unless there is a definite flat area worn or when the tip of the 'shark fin' siping begins to erode at the tip. That's the pointy area in the rearward-facing groove on the sidewall. The grooves are 'siping'.
As long as your tire shows no visible damage such as "ballooning" near a cut or puncture, the belting/casing is fine. It is when you can see threads that you need to worry.
Wheelies don't pop themselves. (from a QBP fortune cookie)
Thanks for replying! You mean seeing threads because the tread is worn really thin, correct? I can look through some of the cracks and see something like threads, but I'll have to look again to be sure. I'll see what I can do getting a picture through one of the cracks...maybe my dying camera will cooperate for one more picture...
Yes, though another indicator of wear is if you find grip is non-existent, means the tyre's worn down pretty far. Most tyres in my experience tend to become un-ridable long before threads start appearing through the rubber!
Oh and I've got holes bigger than that in my MTB tyres, they aren't really a problem. If you're concerned though, whack a couple of layers of Duct tape on the inside of the tyre.
Has anyone ever had a catastrophic tire failure? I don't want to be descending at 40+ mph and have the tread come off in a turn. Sounds like it would hurt... might take more than beer to mouth application to feel good after something like that
My mate had near enough one (though this was mountain biking)
He came down a really rough descent and this sharp rock ripped about a 1" square lump from his rear tyre and made a mess of his rim.
TBH a catastrophic tyre failure other than those assisted by the ground would probably only occur with VERY worn out tyres (the kind with thread poking out I'd imagine). It would most likely be the rear one as well. Rear tyres tend to wear out faster.
I think you'd be incredibly unlucky to get tyre failure, you've still got most of your tread left by the looks of it!
The big cut is definitely a puncture. If you got a flat tire when that hole was made, it means it goes through the rubber tread as well as the casing. Small enough not to worry about, but probably cut the thread under the tread. On little holes like this, not a bad idea to put something inside the tire to reinforce the hole so the tube doesn't try to push itself through the opening.
The little cracks are not so much "wear" as the resiliency of the rubber breaking down due to exposure to UV light and ozone in the air. In and of themselves, they're no worry. But they do mean that the side wall casing is probably also loosing its strength and may start cracking too. It may also mean you don't get the same traction you did when the tire was new. In rough terms, the rubber is hardening up.
For riding around on casually, I would definitely keep riding this tire as long as I didn't see big cracks appearing in the sidewall. But if I was regularly bombing down hills at 40+, I'd get new tires.