I have a 1996 model bike with the original tires. There is very little wear on the tires, but they are showing some cracks due to age. No bulges, though.

Most folks would say to toss 'em, but I respect Sheldon Brown's view that cracks in the tire are harmless. I'm guessing the theory is that the belts in the tire hold it together, not the rubber, so the integrity of the rubber is not that important.

There's also the view that the cracks will let the weather in to degrade the belts and the tire will soon become unsafe.

So what do you think?



Sheldon Brown says:

Many cyclists waste money replacing perfectly functional tires simply because they're old, or may have discolored sidewalls. If you just want new tires because the old ones look grotty, it's your money, but if you are mainly concerned with safety/function, there are only two reasons for replacing old tires:

1. When the tread is worn so thin that you start getting a lot of flats from small pieces of glass and the like, or the fabric shows through the rubber.
2. When the tire's fabric has been damaged, so that the tire has a lumpy, irregular appearance somewhere, or the tube bulges through the tire.

Cracks in the tread are harmless. Small punctures in the tire such as are typically caused by nails, tacks, thorns or glas slivers are also harmless to the tire, since the tire doesn't need to be air-tight.
Gum-wall tires sometimes get unsightly blistering on the sidewalls from ozone damage. (This is frequently caused by storing the bike near a furnace--the powerful electric motors in typical furnaces can put a fair amount of ozone into the air.) This blistering is ugly, but doesn't actually compromise the safety/reliability of the tire in the least.

https://www.sheldonbrown.com/tires.html

This is the word of Sheldon and it is good.

You know, most of the time Shedlon is right. It would take an unusual circumstance for a crack to turn into a catstrophic tear, at say 45 mph, dumping you and mangling your body.

Personally, I wouldn't even consider it.

they're definitely dangerous on your car...tons of heat builds up with all the friction and can cause a blowout (happened to me).

but i doubt enough heat could build up in a bicycle tire for it to end up catastrophically.

It really all depends on severity. If there some slight cracking going on I'm not going to panic over it, but the closer they get to looking like the Grand Canyon, the more concern I have.

As for 45mph on my bike... Ha! I'm lucky to see 20 going downhill thith a tail wind and my pockets filled with lead weights.

I just replaced a set on my road bike. They were pretty cracked up ... then the rubber started flaking off in chunks. I can see that being problematic while cornering