How far can you drive on a punctured run-flat?
Most run-flat tyres are rated for around 50 miles at up to 50mph after losing all their pressure. The exact figure is set by the tyre manufacturer and some are rated for less, so the number printed in your handbook beats any general rule.
The important word is rated, not safe indefinitely. That distance exists so you can get off the motorway and to a fitter, not so you can finish the week on it. Every one of those miles is the reinforced sidewall carrying the entire weight of the car on its own, heating up as it goes.
The other thing to understand is when the clock starts. A run-flat looks and feels almost normal when it is flat, which is exactly the point of it, and it is also the problem: without the tyre pressure monitoring system telling you, you may have no idea you are on the 50-mile allowance at all. If your TPMS warning light comes on in a car with run-flats, treat it as urgent rather than as a nuisance.
Can a run-flat with a nail in it be repaired?
Usually not, and it catches people out because the damage looks so ordinary.
Most run-flat manufacturers do not permit a repair once the tyre has been driven on while deflated, and several do not permit repair of a run-flat at all under any circumstances. The reasoning is sound. The whole design depends on a reinforced sidewall carrying the car without air, and running it in that condition degrades the sidewall internally. That damage cannot be assessed from outside the tyre, and a repair that relies on an intact structure is worthless if the structure has already been compromised.
The general UK repair rules apply on top of that. Under the principles of British Standard BS AU 159, a repair is only permitted for minor damage in the central tread area of a tyre that has not been driven flat. A run-flat that has done its job has by definition been driven flat.
So the realistic answer for most drivers with a nail in a run-flat is a replacement. We would rather tell you that on the phone than turn up and surprise you with it. In the small number of cases where the tyre has not lost pressure, the damage is squarely in the tread and the manufacturer permits repair, we will say so.
How to tell if you have run-flats
Look at the sidewall for one of these markings. They all mean the same thing, with different manufacturers using different letters:
- RFT (Bridgestone, and used generically)
- ROF or ZP (Continental, Michelin, Pirelli)
- RSC (BMW and Mini, “Run-flat System Component”)
- EMT (Goodyear)
- SSR (Continental)
- DSST (Dunlop)
Two other clues: a car on run-flats usually has no spare wheel anywhere in the boot, and it will always have a tyre pressure monitoring system, because the tyre cannot be trusted to tell you itself.
If you are not sure, send us the registration and we will tell you what your vehicle should be running.
Can you switch to normal tyres?
Often yes, technically. Whether you should is a different question.
Points worth weighing before you do:
- Some manufacturers specify run-flats for the vehicle, and switching may affect how the car behaves and how a warranty or insurance question is viewed.
- The car was set up around a stiffer sidewall. Ride quality usually improves on conventional tyres, and handling changes with it.
- There is no spare wheel in the boot to fall back on. If you switch, you need a plan for a puncture, which realistically means a sealant kit and the number of somebody who comes to you.
- Do it as a full set. Mixing run-flats and conventional tyres across an axle gives the car two different sidewall stiffnesses to work with, which is not a sensible place to save money.
We are happy to talk it through rather than just quote you whatever is cheapest. It is your car and your call, but you should make it with the full picture.
Do they have to go in pairs?
There is no law requiring it. On the same axle it is usually the right call, and slightly more so on run-flats than on conventional tyres, because so much of the car’s handling depends on the two sidewalls behaving the same way.
If the other tyre on that axle is recent and has plenty of tread, one is often perfectly fine. If it is half worn, matching them is the better long-term buy. We will tell you which of those you are actually looking at, rather than defaulting to the answer that sells more tyres. Our guide on replacing all four tyres at once goes into when it does and does not make sense.
Getting a run-flat fitted where you are
Run-flats need more force to break off the rim than a conventional tyre and they need balancing properly afterwards. That means a van with real equipment on board, not a compressor and optimism.
Ours carries professional-grade balancing equipment, so run-flats, low profiles, performance tyres and picky TPMS sensors are routine rather than a problem. We cover Dundee, Perth, Angus, Perthshire and Fife, 24 hours a day, at your home, your workplace or the roadside.
Get a price for your car or call Matt on 07449 206 581.