Run-flat tires explained
A run-flat has a reinforced sidewall so it can be driven a limited distance at reduced speed after it loses pressure. The exact limit is the one for that tire and vehicle, and a punctured run-flat may not look flat.
Updated
What “run-flat” actually means
A run-flat tire has a reinforced sidewall so it can carry the vehicle for a limited distance after it loses pressure, at a reduced speed. The distance and the speed are set by the tire maker and the vehicle maker. They are not one number for every run-flat. Read the guidance for the tire that is on the car. Do not borrow a figure from a different brand.
The size still looks like a normal size, such as 225/45R18. Run-flat construction is marked separately on the sidewall. Brands use their own names. The letter R in the size still means radial, not run-flat.
A run-flat may not look flat
Because the sidewall holds the car up, a punctured run-flat can look almost normal. The pressure warning is the signal. Keep to the speed and distance in the vehicle’s instructions and go to a Shop. Driving farther because the car “feels fine” is how the sidewall, and sometimes the Wheel, gets destroyed.
Many cars that came on run-flats have no spare. That is a design choice, not a sign that the tire can be ignored.
Repair and replacement are brand-specific
Some tire makers allow one tread-area repair on a run-flat under strict conditions. Others say a run-flat that has been driven at zero pressure must be replaced. Follow the brand that made the tire. A shop that agrees with you against the brand’s rule is not doing you a favour.
Not every shop will demount a run-flat. The bead is stiffer. Ask before you arrive, and say it is a run-flat. Tire-Finder does not know which shops will take the job unless that shop recorded run-flat service on its listing, and even then you should confirm.
Replacing them
Match the size, load index, and speed rating. If the car was designed for run-flats and has no spare, replacing them with ordinary tires leaves you without the run-flat backup the car was built around. That can be a valid choice if you carry a spare or a plan, but it should be a choice you make on purpose.
Common questions
How far can I drive on a flat run-flat?
Use the distance and speed in the instructions for that tire and vehicle. There is no single limit that covers every run-flat, so this guide does not print one.
Can any tire shop repair a run-flat?
No. Some brands do not allow a repair after the tire has been driven flat, and some shops will not demount run-flats. Ask the shop and follow the tire maker.