Fix-A-Flat: Miracle Or Nightmare?

What you need to know

A flat tire on a car

Ildar Sagdejev/Wikimedia Commons/CC BY-SA 4.0

Fix-A-Flat is marketed as basically being the equivalent to an instant spare tire, an aerosol can containing a mysterious substance that will not only patch a hole in your tire right by the side of the road but inflate it as well! But is it really as good as it claims to be?

We're somewhat unenthused but will admit it has (limited) uses.

Use Caution With Older Cans

Depending on the age of the can, Fix-A-Flat can be:

  • Flammable/Explosive.
  • Toxic.
  • Acidic.
  • Some combination of all of the above.

Older cans of Fix-A-Flat contain either propane or butane as a propellant and tire filler, which can be dangerous, as both substances are flammable and explosive. Somehow the idea that tires heat up when driven, or that deflating the tire might happen in a shop environment where sparks and flames might be present never really seems to have occurred to the people making the stuff. This also led to numerous anecdotes of exploding tires, or corroded or rusted cans left in hot cars exploding in trunks and damaging everything in the vicinity.

The Issue of Propellants

Even with propane or butane no longer being a problem, the issue of propellants still remained. At first, the propellant was a hydrofluorocarbon called HFC-134a, which is nonflammable, but which is a major greenhouse gas. To give an idea of how major: The potential of any chemical to contribute to global warming is called its Global Warming Potential. Carbon dioxide has a Global Warming Potential (GWP) of 1, the standard by which all GWP is measured. HFC-134a has a GWP of 1,300. Now the propellant used is called hydrofluoroolefin (HFO) and has a GWP of 6.

The Liquid Remains in Your Tire

However, that does not solve all problems. The way this stuff works is that the propellant is also a polymer. When that polymer is combined with an acid solution and exposed to oxygen, a catalytic reaction takes place that turns the polymer into an epoxy, which seals small nail holes. Unfortunately, the resulting liquid, which is highly acidic, remains in your tire and must be cleaned out if the tire is not to be further damaged by acid, not to mention that the liquid makes the tire impossible to balance. It's also a smelly, toxic, ugly mess to clean out. Have you ever tried to get liquid out of a tire? Many tire shops will simply refuse to do it at all. Some will simply charge more to do it.

Will Only Fix Nail Holes

Keep in mind that Fix-A-Flat will only fix nail holes. Larger damage, wheel bends, cracks or sidewall issues are not repairable with epoxy. This becomes extremely important when an automaker that uses runflat tires decides that you don't need a spare because Fix-A-Flat will do. It won't, not for all possibilities. If the sidewall is damaged, you're out of luck. If the wheel becomes bent enough to lose contact with the tire, or if the metal cracks due to impact, you're out of luck.

If you absolutely have to use Fix-A-Flat, when you do take the tire in for repair, please don't forget to tell the tire people that you put it in your tire! Don't make them figure it out when they open the valve to deflate your tire and a toxic, acidic liquid comes flying out! We hate it when that happens

Watch Now: Change a Tire - Replacing Flat Tire With a Spare