Popular Mechanics has put up two very useful short articles about what causes tires to blow out, and how to deal with the situation when they do. You’ll find them at these links:
Dealing with a blowout is NOT intuitive, and the technique isn’t what you’d expect. Highly recommended reading for all drivers.
Peter
Check the air in a mini spare tire regularly.
They lose air through the tire carcass, so they never have enough pressure. Most require 60 psi, but I found they typically only have 15-20 psi when you need them. It will fail very quickly at highway speeds with so little pressure.
In 4+ years of patrolling the freeways here in CA, I only found 3 of them with the correct pressure, and that includes rental cars.
After you mount one of them, slow down! They have a speed limit of 50mph, IIRC. And if you are transporting a load, get off the highway and go even slower. They are intended only to get you to the closest tire service you can find.
I used to drive gasoline tankers. The company taught us to immed hit the throttle if we got a blowout – to counteract the physics of the vehicle being pulled in the direction of the blowout. Then gradually move to the right while slowing. Of course, the fact that you were hauling liquids contributed to the slosh effect. Made me 'get religion' more than once…