Do those fancy cans of “anti-puncture” foam work? If so, why aren’t all tyres treated with this chemical to prevent punctures in the first place? Liz
Keeping a can or two of tyre foam in your toolkit is well worth it. - they can be a godsend in a few situations. However, the benefits are brief and limited.
If you get a small puncture at a dangerous or inconvenient moment, they can get you going again in about one minute – without jacking up the car or removing the wheel or using of any other equipment.
They contain a liquid polymer, compressed gases and sealants which you squirt in through the tyre valve. The process is as simple as pressing the button on a can of insect spray.
The gases restore some inflation to the tyre, and the sealants froth up and flow around the inside of the casing to cover up and plug the hole that caused the flat.
The fix can help you get to a safer place or a repair shop…if the leak is in the tread and not much bigger than the diameter of a thin drinking straw. They are unlikely to be effective for larger holes or for gashes in the sidewall.
A single can will reinflate the tyre of a bicycle or ride-on lawnmower but will only partially reinflate the average (usually tubeless) car tyre.
Several cans would be necessary to get a completely flat tyre of a big 4x4 back into shape. But you can motor for a significant distance – slowly – with an under-pressure tyre as long as it is inflated enough to ensure the wheel rim does not pinch the tyre’s sidewall.
If you spot a “soft” tyre well before it is completely flat, the cause will be either a faulty valve or a “pin-prick” (slow) puncture. Foams will likely reinflate the tyre more fully and cover these the pin-pricks for some time, but the cure cannot be relied on indefinitely. The foam progressively degrades and can eventually crack and become ineffective.
You can follow a foam-fix with a tubeless repair plug without demounting the tyre. It would be helpful to know exactly where the hole is/was, and it would be surer to replace the valve with a new one.
The go-to “extra” equipment is a tubeless puncture repair kit and an air pump that runs off the car battery
Photo credit: Shutterstock
Ultimately, tyre foams can get you out of trouble in an emergency, but the time and effort they save on the spot will come back to bite your watch and your wallet later. When a tube repair is conducted, the casing will be extra messy and have to be cleaned before conventional fix and balance are attended to.
These aerosol foams should not be confused with forms of pre-treatment that claim to make tyres more puncture-resistant – permanently.
These use different chemicals, must be done in a specialised workshop, and are not cheap.
Given that the tyre casing itself is extremely strong and resistant to punctures in the first place, the rationale of pre=treatment concoctions is that they are viscous enough to plug any hole left by a nail or thorn, but also remain liquid enough to flow into that location.
In much of the world, advanced tyre technology and good road conditions have made punctures very rare, to the extent that some cars carry a “skinny” spare wheel to save weight, and others just carry foam (which saves the weight of a spare and the jack).
In Kenya, even the tarmac can be a puncture minefield and safaris on dirt roads and even off-road are common.
The go-to “extra” equipment is a tubeless puncture repair kit and an air pump that runs off the car battery…to go with the standard jack with a block of wood to stand it on (sometimes also a hi-lift jack), and two spare wheels.
For expeditionary (!) motoring, add tyre levers and perhaps a healthy tube as an inner patch.
