When I came home today from by bike ride I found my tire like this:
I understand that I'll need to change my tire. My question is how urgent is this? Can I just keep using the tire until it stops holding air, or is this dangerous, and the it might pop when I'm on the bike?
That’s really bad. Replace that tire immediately, before the next ride for sure.
When you can see the cloth skeleton of the tire, that means it’s finished. The cloth is nowhere near as abrasion resistant as the rubber, and you’ll soon rub through it. When that happens, the tire is likely to fail dramatically in something known as a “blowout”. This is a very sudden event that leads to a high risk of crashing. Don’t tell yourself that you’re skilled enough to ride it out, it’s just not worth the risk.
Furthermore, see how the side of the tire is fuzzy? That means the cloth on the sides is damaged. If it tears, again, your tire might explode and you will likely crash. Do not try to risk it.
Edit: Realize that it is not the tire which holds air. The tire itself is porous. From a pneumatics viewpoint, it only serves as the mechanical device resisting the 70+ psi outwards force from the air. Inside the tire, there is another rubber donut, which is an impermeable bladder known as your “inner tube”. This inner tube is not strong enough to hold that amount of pressure by itself. Henceforth, when you wear through enough of the outer tire, it will fail to be strong enough to resist that 70psi and subsequently tear. The weak inner tube will then expand through the tear and burst because it isn’t being contained by the tire anymore. Although it will become easier to puncture the tube as the tire wears down, it will not give you any major advance warning (you might hear cloth ripping and threads breaking, or you might not. Depends on your luck and the exact cause of tire failure. Hitting something like a sharp rock definitely will not give any warning) before it lets go altogether. Since it is only the inner tube which holds air, the tire will keep on going until it instantly rips apart.
Congratulations for riding so much you’ve worn a tire out though! That’s awesome!
I understand that I'll need to change my tire. My question is how urgent is this? Can I just keep using the tire until it stops holding air, or is this dangerous, and the it might pop when I'm on the bike?
Seeing the cords in the tire casing is THE sign that the tire needs to be replaced. (Some tires have wear indicators, but they are overly cautious, so you should use the "do you see the cords?" test if you want maximal tire life.) It your case, you probably should have replaced the tire a bit earlier as the cords have been visible quite a lot of time judging from the size of the hole. But it's not too late.
The hole showing the cords is so large that you are living on borrowed time. The cords will wear. Eventually, the tire will burst, because the cords can no longer hold the pressure after being damaged, and the explosion will cause the tube to burst. A tube bursting in such a way cannot be patched easily.
I would not use the tire for anything except 1km shopping run, if following these procedures:
These will extend the safe life of the tire a kilometer at a time. It is unlikely that if the tire holds 7 bars of pressure before riding a kilometer, that the cords would wear so much that it can't hold 5 bars of pressure after riding a kilometer.
In my opinion, doing this safety check every kilometer is unacceptable, so it's best to simply replace the tire.
When replacing the tire, put the new tire to the front, and move the old front tire to the rear if it was the rear tire that was worn out. Front tires wear so little that the tire will die of old age instead of dying due to wear. You will always want to have the better tire in the front, or else the front tire wears so little it's at danger of disintegrating due to old age. A front tire blowout is much more dangerous than a rear tire blowout.
