Is it true that you cannot patch run-flat tyres after they have been punctured?
In some cases, patching is still possible. If patching cannot be done and the only solution is to buy a new tyre, then the running cost of such tyres would be higher than that of conventional tyres. Usually, you must change at least two tyres when this happens.
As the name suggests, run-flat tyres allow the car to be driven despite a partial or even total loss of air pressure. This is possible because the tyres are constructed with specially reinforced side walls so that the tread continues to maintain surface contact with the road, providing a sufficient level of grip and stability.
But there are limitations to how far and how fast you can drive with a punctured run-flat tyre. Currently, the makers that offer such tyres warn not to exceed a specified maximum speed and distance.
The tyre can be repaired in the conventional way by patching up the puncture "wound". However, this will largely depend on just how old the tyre is. If it is already halfway near replacement point, it is best to just replace it.
With run-flats, you will never be stranded with a puncture. And you will not need to carry a spare and a jack.
But they do cost more than regular tyres. And they are often less comfortable than regular tyres.