How do I know if my car has run-flat tyres?

Check the sidewall for codes like RFT, RSC, ROF, SSR, ZP or EMT. Or check the spare wheel well — if there's no spare and no jack, your car almost certainly came on run-flats.

Can I drive 100 miles on a run-flat tyre?

No. The manufacturer limit is 50 miles at 50 mph. Beyond that, heat damage can cause sudden failure even after the puncture is fixed.

Are run-flat tyres worth it?

For city drivers who'd otherwise be stranded with no spare — yes. For drivers who don't mind a mobility kit and want softer ride quality — switching to standards is often the better call.

Why are run-flat tyres so expensive?

The reinforced sidewall uses specialist heat-resistant compounds and requires more material. Manufacturers also build them to tighter tolerances because failure modes are less forgiving.

Run-Flat Tyres Explained: How They Work & When to Replace

If you drive a BMW, Mini, MG, Lexus or many newer Mercedes, your car almost certainly came on run-flat tyres — and there's a good chance you don't have a spare wheel in the boot. Run-flats let you keep driving after a puncture, but they come with rules most drivers are never told. This is what every London driver should know.

How a run-flat tyre actually works

There are two main types of run-flat in the UK: self-supporting (SST/RFT) and auxiliary-supported. Around 95% of cars on London roads use the self-supporting design.

Self-supporting run-flats

The sidewall is roughly 4–5x thicker than a standard tyre and reinforced with heat-resistant rubber compounds. When pressure is lost, the sidewall doesn't fold — it carries the car's weight directly on its own structure for a limited distance.

Auxiliary-supported (PAX system)

Rare in the UK — found on some early-2000s Renaults. A solid rubber ring sits on a special wheel inside the tyre. If you've got these, you'll know — replacements need specialist fitting.

The 50-mile, 50-mph rule

Every major manufacturer (Bridgestone, Continental, Michelin, Pirelli, Goodyear) publishes the same limit: after a puncture, a run-flat can be driven approximately 50 miles at a maximum of 50 mph. This is enough to get you off a motorway and to a tyre fitter — not enough to finish your commute and deal with it tomorrow.

Can run-flat tyres be repaired?

In almost every case: no. Three reasons:

Once driven flat, the internal structure suffers heat damage that's invisible from the outside.
British Standard BS AU 159 specifically prohibits repair of any tyre run flat or under-inflated.
Bridgestone, Pirelli and Continental explicitly void their warranty on any repaired run-flat.

There are two edge cases where repair may be allowed: the puncture is in the central tread (not the shoulder), AND the tyre was never driven below 15 PSI. A qualified fitter will check both conditions before touching it.

What replacement costs in London

Run-flats cost 30–50% more than equivalent standard tyres. Typical London prices for a 225/45 R18 fitted at the roadside:

Budget run-flat (Linglong, Nankang): £140–£180
Mid-range (Bridgestone Driveguard, Hankook): £180–£240
Premium (Pirelli P Zero RFT, Continental SSR): £240–£340

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The comfort trade-off

Stiffer sidewalls transmit more road noise and impact harshness. On London's tarmac (rougher than most UK cities thanks to constant utility roadworks), some drivers swap their run-flats for standard tyres and carry a tyre-mobility kit instead. This is legal and usually invalidates nothing in your insurance — but check your policy, and never mix run-flats and standards on the same axle.

Can you mix run-flats with standard tyres?

Legally yes in the UK. Practically: never on the same axle, and ideally not on the same car. The braking and handling balance is calibrated for matched tyres. Insurers may push back on a claim if mismatched tyres are deemed a contributing factor.