13 hours ago
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Having a spare tyre is becoming an increasingly complex ask. Manufacturers have done away with the extra wheel to save space and weight, with some electrified cars simply not having the boot space for such a thing.
While some brands offer a tyre repair kit that has what’s called a plug, which we have covered here, some brands offer a sealant spray or tyre goo – best known by its brand name 'Fix-a-Flat'.
The idea is simple: you get a puncture, you spray the goo or sealant into your tyre, inflate it as much as you can, and while you drive, this goo is essentially going to work plugging the gap.
But how does it do it, and does it actually work?
How does tyre sealant work?
Each brand has a different formula that they hold very close to their chest, but the best way to think of it is like a craft glue. It's incredibly malleable when wet, but fast drying and weirdly flexible when it does dry.
The idea is that you dump a heap of this tyre sealant into the valve stem on your wheel. While you drive, the centrifugal force will spread it across the inside of the tyre, plus the escaping air will attract the goo to that specific spot.
Going more in-depth, some tyre sealants that use an earlier formula of a latex base have a liquid that enlists the help of leaking air to essentially dry out the latex or react with ammonia to plug a hole and quickly dry the formula.
Now, a fair few modern sealants use a glycol base that the Institute of Making, a research club for real-world materials, in the United Kingdom does a good job of explaining the complex nature of it.
“Glycol-based tyre sealants last a lot longer as they don’t rely on a chemical change to solidify them, so they can stay liquid for longer, and they can function down to -37°C. Sealants like this one are made up of hundreds of tiny fibres and inorganic fillers that are suspended in a carrier of either propylene glycol or ethylene glycol and water," the Institute of Making's website says.
“When a hole forms in the rubber tyre, the pressure of the air escaping the tyre pushes the sealant into the cavity. The hundreds of tiny fibres in the sealant snag on the rubber and each other, intertwining and bonding to the rubber cavity. As the tyre rotates, the rubber flexes and more fibres are packed into the hole until no more will fit.”
Some brands offer a product that is a preventative measure rather than a fix. There are a few renditions. Some that you spray into an already fitted tyre and allow it to solidify while you drive, and others that use a machine to spray it into the tyre before it is fitted.
They’re all similar properties; a sticky silicone-based spray that 'self-heals' small punctures. This technology isn’t readily available in Australia as of yet and has not been locally tested.
Does tyre sealant spray work?
It works well for a short period of time to at least slow the air leak from your tyre. However, for it to work correctly, the puncture must occur within the tread line.
If the sidewall or wheel has damage, then you should stop immediately to get the wheel or tyre replaced.
The idea of a tyre sealant is that it is supposed to get you to the nearest tyre shop to either replace or plug the punctured tyre. Because you are essentially spraying a thin film in to hold air, and it is certainly no replacement for a plug kit that adds more rubber material into the tyre.
Zane Dobie comes from a background of motorcycle journalism, working for notable titles such as Australian Motorcycle News Magazine, Just Bikes and BikeReview. Despite his fresh age, Zane brings a lifetime of racing and hands-on experience. His passion now resides on four wheels as an avid car collector, restorer, drift car pilot and weekend go-kart racer.
