Emergency Tyre Repair: Foam Sealants vs Spare Tyres

The spare wheel has been disappearing from new cars for over a decade. Manufacturers eliminate it to save weight, cost, and boot space — and because the prevalence of mobile phones and breakdown services has reduced the number of drivers who can or will change a tyre themselves. Run-flat tyres and tyre foam kits are offered as alternatives.

For many drivers in urban areas with good mobile coverage and breakdown membership, the absence of a spare wheel is a manageable compromise. For drivers who regularly travel in remote areas or who aren't comfortable relying on a call-out service, it's a more significant concern.

Tyre foam kits — typically consisting of a can of sealant and a compressor — work by injecting a latex-based foam into the tyre through the valve stem. The foam coats the inside of the tyre and seals small punctures as the tyre is inflated and driven on. They're quick to use and require no physical effort to deploy.

The limitations are significant, however. Foam sealants only work on tread punctures — they cannot seal sidewall damage or blowouts. They work best on punctures up to about 4mm in diameter. Once used, the tyre is contaminated with sealant and typically cannot be repaired — it must be replaced. TPMS sensors can also be damaged by some sealants.

If your car came without a spare wheel and you're concerned, consider purchasing a space-saver spare wheel and tyre to store in the boot — many vehicles have a spare wheel well that accommodates a space-saver even if the manufacturer didn't include one. It provides more flexibility than foam alone, particularly for longer journeys.

At a minimum, ensure your tyre foam kit is not expired (the sealant has a shelf life — check the can) and that your compressor works. Know how to use the kit before you need it in a stressful roadside situation. And always have a breakdown membership or roadside assistance plan as a backup.