How Run-Flat Tyres Work
A standard tyre relies entirely on air pressure to support the weight of the vehicle. When that pressure drops to zero — from a puncture, a nail, or a slow leak — the tyre collapses and the vehicle becomes undriveable. Run-flat tyres solve this problem through a fundamentally different construction.
The key difference is the reinforced sidewall. Run-flat tyres incorporate a thick, heat-resistant rubber insert in the sidewall that can support the vehicle's weight even when there is no air pressure inside the tyre. This allows the driver to continue travelling at a reduced speed for a limited distance, giving them time to reach a safe location rather than stopping immediately in a dangerous position.
There are two main technologies used. The most common — called Self-Supporting Run-flat (SSR) — uses the thickened sidewall insert described above. A less common variant uses a support ring fitted inside the wheel that the deflated tyre can rest on. Both serve the same purpose: keeping the vehicle stable and steerable after a loss of tyre pressure.
Because run-flat vehicles do not need to carry a spare tyre, manufacturers — particularly BMW, Mini, and Rolls-Royce — have fitted them as standard equipment for many years. The saved weight and boot space are considered significant advantages for these brands.
How Far Can You Drive on a Run-Flat Tyre?
The industry-standard guideline is a maximum of 50 miles at no more than 50 mph after a complete loss of tyre pressure. However, this varies between manufacturers. Some run-flats are rated for shorter distances or lower speeds — always check your vehicle handbook for the specific limits that apply to your tyres.
Your tyre pressure monitoring system (TPMS) will alert you when pressure drops. The moment the warning light activates, reduce your speed immediately. Do not attempt to maintain normal motorway speeds on a run-flat tyre in deflated mode — doing so risks overheating the sidewall insert and causing a sudden loss of control.
The 50-mile limit is a maximum under ideal conditions. London stop-start driving, speed bumps, and pothole-heavy roads will reduce the effective range. As soon as you can stop safely, call for assistance.
Why Most Run-Flat Tyres Cannot Be Repaired
This is the most important thing London drivers need to understand about run-flat tyres, and it is the point where most people are caught off-guard.
When a run-flat tyre is driven in deflated mode, the reinforced sidewall flexes under a level of stress and heat that it was not designed to sustain indefinitely. This causes internal structural damage — to the rubber compound and the fabric reinforcement layers within the sidewall — that is not visible from the outside. The tyre may look perfectly intact externally, with no visible cracks or deformation, yet the internal structure has been compromised.
Repairing a puncture in such a tyre and returning it to service would conceal this hidden damage, creating a tyre that could fail catastrophically at speed. For this reason, the British Standard BS AU 159 — which governs tyre repairs in the UK — effectively prohibits repair of run-flat tyres that have been operated in run-flat mode.
The only exception is a run-flat tyre that has not been driven on while flat. If, for example, your TPMS alert activates while you are stationary or moving at very low speed and you stop immediately — and the damage is a small nail in the central tread area — a tyre professional may assess the tyre as a candidate for repair on a case-by-case basis. This is a narrow exception, not the norm.
How to Identify Run-Flat Tyres
Run-flat tyres are marked on the sidewall, but the marking varies by manufacturer. Look for one of these codes:
- RFT — Bridgestone's run-flat designation
- ROF — Run On Flat (used by several manufacturers)
- SSR — Self-Supporting Run-flat (Continental)
- EMT — Extended Mobility Tyre (Goodyear/Dunlop)
- ZP — Zero Pressure (Michelin)
- RSC — Run-flat System Component (Bridgestone OEM)
If your car does not have a spare tyre and no tyre inflation kit is present in the boot, it is almost certain your vehicle came factory-fitted with run-flats. If you are unsure, your vehicle handbook will confirm it, or call us and we can advise based on your registration number.
Cost of Run-Flat Tyre Replacement
Run-flat tyres cost approximately 20 to 40% more than an equivalent standard tyre from the same manufacturer. This premium reflects the more complex construction and higher-grade materials used in the sidewall reinforcement. For a popular BMW 3 Series size such as 225/45 R17, a mid-range run-flat tyre typically costs £90 to £130 per tyre, compared to £65 to £95 for a standard equivalent.
Fitting time is broadly the same as for a standard tyre. FixMyTyreNow carries run-flat stock for most popular vehicle fitments and can replace your tyres at your home, workplace, or roadside location across all 32 London boroughs. Our run-flat replacement service starts from £110, including fitting and wheel balancing.
Frequently Asked Questions
How far can I drive on a run-flat tyre?
Most run-flat tyres allow you to drive up to 50 miles at a maximum speed of 50 mph after a loss of pressure. This varies by manufacturer — always check your vehicle handbook. The run-flat warning light will activate when pressure drops, at which point you should reduce speed immediately.
Can a run-flat tyre be repaired after a puncture?
In most cases, no. Once a run-flat tyre has been driven in run-flat mode (with zero or near-zero pressure), the internal reinforced sidewall sustains heat and stress damage that is not visible externally. Repairing the tyre would conceal this damage, making it unsafe. Only run-flat tyres that have not been driven flat — with a small nail in the central tread — may be candidates for repair on a case-by-case basis.
How do I know if I have run-flat tyres?
Look for the letters RFT, ROF, SSR, EMT, or ZP on the tyre sidewall, or check your vehicle handbook. Run-flat cars do not have a spare tyre. If your car came without a spare and has no tyre inflation kit, it almost certainly has run-flats fitted.
Are run-flat tyres more expensive to replace?
Yes. Run-flat tyres cost approximately 20–40% more than equivalent standard tyres due to the reinforced sidewall construction. Fitting time is similar. FixMyTyreNow carries run-flat stock for most popular vehicles and can replace them at your location across London.