What is a run-flat tyre? How runflats work, codes and limits

A run-flat tyre (also written runflat or RFT) is a tyre with reinforced sidewalls that keep carrying the weight of the car after it loses air. Instead of going flat, it lets you keep driving for a limited distance, usually about 80 km at up to 80 km/h, so you can reach a workshop instead of changing a wheel where you lost the air.

That is the short answer. Below is how they work, how to tell if your car has them, the limits each maker gives, and what to do after a puncture.

How does a run-flat tyre work?

A normal tyre is held up by the air inside it. When the air goes, the sidewalls fold and the car sits on the rim.

A run-flat has much stiffer sidewalls. Michelin describes "reinforced sidewalls that help support the car's weight". Continental says a "specially designed reinforced sidewall supports the tire" after a puncture. Goodyear describes reinforced shoulders and highly resilient rubber inserts that support the weight of the car.

Makers call this a self-supporting tyre. Continental's name is SSR, short for self-supporting runflat. Pirelli calls its version Self-Supporting RUN FLAT.

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

Look at the tyre sidewall, next to the size. Each maker uses its own marking:

Michelin's guide also lists SST and BSR among the codes used. Other makers use their own symbols, as Goodyear notes, so if you see an unfamiliar code next to the size, check it with the tyre maker.

Two other clues: run-flats are fitted with a tyre pressure warning on the dashboard, and the car often has no spare wheel. Our guide on how to read your tyre size shows where the markings sit.

How far and how fast can you drive on a run-flat?

Every maker gives a limit. They are close, but not the same:

These are upper limits, not targets. Michelin says the figures vary by tyre profile and maker, and that the real range depends on the load in your car, the outside temperature and the road. Goodyear says to follow your vehicle handbook where it gives different figures, and warns that going further or faster causes excessive wear and heat.

Why do run-flats need a tyre pressure warning?

Because you may not feel the puncture. A run-flat holds its shape with no air in it, so the car can feel almost normal.

Michelin, Goodyear and Continental all say a car on run-flats must have a tyre pressure monitoring system (TPMS). The dashboard warning is how you know a tyre has lost air. When it comes on, slow down, stay within the maker's limits, and get the tyre checked as soon as you can.

Can a run-flat tyre be repaired?

Sometimes. Michelin says its run-flats can be repaired once, by a professional, unless the sidewall says otherwise, and not in every case. Goodyear says not all makers' run-flats can be repaired, though some of its own can be, by a qualified tyre professional.

Continental advises having the tyre checked by a specialist as soon as possible after a puncture. A tyre that has been driven on with no air has worked hard, so let a professional decide whether it can go back into service.

Can I fit run-flats to any car?

Not always. Michelin says run-flats should only go on rims with a double hump and on cars where the car maker has approved them, and it does not recommend fitting them to a car that was not designed for them. Michelin recommends a full set of four.

Continental says its SSR tyres fit all standard rims and are developed especially for low-profile tyres. Goodyear says run-flats can be fitted to normal alloy wheels, but only on a car with TPMS.

The safe route is to follow your car maker's handbook, and to ask a tyre professional before you switch to or from run-flats.

Advantages of run-flat tyres

You keep moving after a puncture. Pirelli's line is that you can drive home safely, within the 80 km and 80 km/h limits. You avoid changing a wheel on a busy road or in the dark.

No spare wheel. Michelin and Continental both say a spare is no longer needed. That frees boot space, which Continental puts at up to 80 litres, and Michelin and Pirelli note the weight saved.

Handling. Continental says that under normal conditions its SSR tyres have no impact on driving or handling.

What run-flats do not do

They do not stop punctures, and they are not a permanent fix. Michelin is clear that you cannot ignore a puncture on a run-flat: you still need to visit a workshop soon. Once you are past the maker's limits, a run-flat is a flat tyre like any other.

Run-flat tyres or normal tyres with a Multiband?

Run-flats are one way to deal with a flat. Another is to keep normal tyres and fit a Tyron Multiband inside the wheel. The band keeps a flat tyre locked on the rim, so you keep steering and brakes and can drive a medium distance at reduced speed to a safe stop. It does not let you drive on to the next town the way a run-flat can.

We compare the two side by side in run-flat tyres vs normal tyres with a Multiband. If your car is on run-flats now and they are due for replacement, see replacing run-flat tyres with normal tyres.

Quick answers

Is runflat the same as run-flat? Yes. Runflat, run flat, run-flat and RFT all mean the same type of tyre.

What does ZP mean on a tyre? ZP is Michelin's marking for its run-flats. It stands for Zero Pressure.

What does ROF mean on a tyre? ROF, or RunOnFlat, is Goodyear's marking for its run-flats.

What does SSR mean on a tyre? SSR is Continental's name for its run-flats: Self-Supporting Runflat.

How long can I drive on a run-flat after a puncture? Most makers give about 80 km at up to 80 km/h. Load, temperature and the road can shorten that, and your vehicle handbook has the final say.

Do I need a spare wheel with run-flats? Michelin and Continental say a spare is no longer needed with run-flats.

Do run-flats need TPMS? Yes. Michelin, Goodyear and Continental all say the car must have a tyre pressure monitoring system.