Why do some tires crack worse than others

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Greetings to all in Bitog land on Saint Stephen's Day! (It's also the day we get to sing about "Good King Wenceslas" - https://www.youtube.com/watch?v=SQVUMG6LZGM).

So, I'm airing up tires this afternoon on my fleet. My compressor is happily humming, inflating all tires in the GreeC fleet to proper pressure.

My neighbor comes over. He has an old car in his driveway that has been sitting there for about three years. The tires are not flat, but low, and he's wondering if he can borrow my nifty compressor to air them up.

"Tell you what" say I, "as soon as I'm done, I'll do it for you."

This is met with approval and as soon as I finish with my own, I head across the street to shoot some air in his tires.

I take my tire pressure gauge with me and discover that the lowest tires has seven pounds and the highest has 13.

I plug my little pancake compressor into his wall socket and begin to pump pounds of air into his almost flat tires.

What I notice is that his four almost flat tires, though worn, don't have a single crack on them. I check the date to determine their age - all of them were made 2007. That's only a year younger than the ones I just pulled off the vehicle formerly known as "Thunder the Wonder Pig." The ones I pulled off my car were loaded with cracks and were starting to split on the sidewalls. His, however, have nary a crack or split on them.

Now, keep in mind, his car has sat for about three years without moving an inch. It's right across the street from where I live so they deal with the exact same weather conditions, (same sun, same rain, same cold and heat, same storms, etc).

Why the difference? Why do his tires look so good while mine are ready for the trash heap, (not because they're worn out. In fact, they still have plenty of tread, but they are cracked to the point of being dangerous)?

I don't remember the brand name, but they're some kind of off brand "all season" radials.

Bitogers, I await your tire wisdom. Meanwhile, I'm finishing a big bowl of collard greens from yesterday's Christmas feast, (cooked with a great big hunk of "fat back").
 
Were your tires Michelins?
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Same sun exposure? I wonder if somehow they get slightly less. Beyond that, different compound. Maybe a low end long life tire?
 
There's an expensive preservative they mix in with the rubber. Yours, they mixed less.
 
Do you run a lot of electric motors near your tires? ozone from the arcing contactors will age rubber pretty fast, but you'd expect only the tire constantly in the closest proximity to be affected.

If the neighbors tires never really flexed that much (no miles) the original oils in the rubber will not have worn out.
 
Cracking in tires is caused by 2 things: Flexing and material properties.

Obviously a tire that isn't flexed is less likely to crack. So it might not be a surprise to find a vehicle that has sat for 3 years not to have cracks.

Material properties? All kinds of interesting things here!

There are types of rubber that are more prone that others to cracking. Some tire manufacturers use the less prone types of rubber in the sidewalls because they don't want them to crack.

Some think it is important that the tire look old and used up when the tire is ..... ah ..... old and used.

Some think this is all about performance, and since the only thing sidewalls are supposed to do is protect the ply cords from physical damage, they don't pay attention about how they look over time.

Cracking is obviously a time dependent thing.

So you will find certain brands that are more prone to cracking than other - and it doesn't mean their tires age better.

Then there is the issue of load. LT tires, which carry a lot more load per their physical dimensions than passenger car tires, use a rubber formulation that is stiff and more prone to cracking. Over the road truck tires are even more so.

So there are a bunch of things that affect cracking, and tires do not age the same way.

But the real problem is trying to gauge how a tire is doing as it ages - and cracking is certainly one way. But absence of cracks is NOT an indication that all is well.
 
In your case use (exposure to road chemicals in the rain) and flexing probably have a lot to do with it. I have a 44 year old original full size spare that has been in my trunk for all of those 44 years that looks like new.
 
Originally Posted By: CapriRacer

Some think it is important that the tire look old and used up when the tire is ..... ah ..... old and used.


Is that why Yokohama's turn almost elephant-skin gray by the fourth year?
 
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