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Spare tire blew up

The unused new spare tire on the side of my horse trailer blew up yesterday. It has been really hot (100+ for 2 weeks) up to 109, but it shouldn’t blow up, should it? I took photos. What else should I do? Should I replace the 4 tires on the trailer (same brand, 1000 miles on them).

How old was it? If it was a LT tire, they can hold pressures of 60 psi or more. Couple that with a sun-baked spare tire that was over 10 years old and I can see this happening. Did it look like it had small cracks in it before it blew?

If the other tires are also more than 10 years old and/or show signs of UV damage like sidewall cracks, then, YES, replace those tires, too.

It was new 7/08. It has max psi of 80 and I had 55# in it. It didn’t have any visible cracks (and neither do the ones on the ground).

Yeah, but what is the age of the tires? Especially the spare? Look on the sidewall for the manufacturing date. Check this page to determine the age of the tires:

Was there an actual explosion, or did it just finally split open because of sun damage? This is what happens to old tires that sit in the sun too long. Has it been exposed to sunlight every day since you bought it? The tires on the trailer are under a fender, right? If so, they get less than half the sun exposure.

Oh, I assumed a new tire would be “new”. I read your referal. I just got in from chores and it’s dark outside. I took a flashlight and went out to the trailer but couldn’t find/read the small print. I’ll try it again tomorrow morning in the daylight. Thanks for the info.

You should post your photos!

It exploded. The trailer is normally parked under a tree but it had been parked on the asphalt in front of the barn for the past 2 really hot weeks, with tire fully exposed on south side. KaBoom.
Thanks to you guys and Google, I’m learning alot about tires. After researching, I found that my tire was mfg in China (it’s a “Carlisle ST 225/75R15 Load Range D AQ15DOT AQHH”. The AQ is mfg Meiyan Tire Co, LTD, Miexian, Guangdong in CHina. It does not have a mfg date on it. Nor a treadwear, traction, or temperature indicator.
I also read on that “in 3 years, 1/3 of the (ST) tire’s strength is gone” and “3-5 yrs is the projected life of a normal trailer tire” (regardless of tread depth or appearance"). Also that tires should be protected from direct sunlight (uv rays). Nowhere did any of the tire guides say anything about tires blowing up,but I did find references to spares blowing up in trunks of people’s cars. So it happens.
I also found that I should keep the tires fully inflated (psi is 65#, not 80 - a mistype- but I did have them underinflated. (It seems odd to me that they would be MORE likely to be damaged when underinflated than when fully inflated when hot(wouldn’t underinflation be “protective”?).

Sounds like a simple defective tire to me…An 8-ply rated tire should NEVER “blow up” unless it was damaged (bruise break) or defective…

I have an old Dodge water truck I keep down in Mexico… It has six twenty year old nylon cord 10 ply tires on it and they are all doing fine…It’s 110 degrees down there right now…

Keeping tires properly inflated is important because an under-inflated tire runs hotter and is much more prone to blowing out when used. The spare blowing out, especially when under-inflated, tells me that tire had a defect. Do the others also have a defect? Chinese products are not know for good quality control. Google ‘Chinese Tire Recall’ to see some of the quality problems that have been in the news.

I’d seriously consider replacing them all.

Running tires with less pressure than specified leads to extreme flexing of the sidewalls of the tire. This flexing causes a buildup of heat within the sidewalls, which are the weakest part of the tire. The heat leads to degradation of the tire’s cords, and a weakening of its structural integrity.

To make a long story short, there was probably a flaw in the tire’s sidewall. Whether that was the result of the “traditional” Chinese quality control (very poor) or whether it resulted from chronic underinflation is academic at this point, but hopefully the OP has learned at least two lessons:

Buy good-quality tires (rarely will these be Chinese-made products)
Inflate the tires to the specified pressure