Run-flat tires have been around since the 1980s, but it is now that they are becoming commonplace as optional and even standard equipment. But even though we’ve heard of it, do you know what a run-flat tire is? If we’re good at English, we’ll find the track in its name.
A run-flat tire is a tire that doesn’t become “flat” when we have a puncture on the road. In other words, it is a tire that can circulate even when the air pressure decreases. But you can’t drive with them indefinitely. Its usefulness is given by being able to drive several kilometers to find a workshop or get home.
As a temporary spare, they have a speed limit that is generally set at 80 km/h, and a set distance of around 80 km. In either case, it depends on the manufacturer’s specifications. Some car companies suggest a distance double that figure, but tire manufacturers do not.
Warning: Never touch a punctured wheel because it will heat up significantly. Wait for the tire to cool down before handling it.
How does a run-flat tire work?
There are two types of run-flat tires available on the market, but the idea behind them is the same. In the tire there is a structure that allows it to maintain its shape even after a partial or total loss of air pressure.
The most common type of run-flat is one with a reinforced sidewall that prevents the rubber from deforming, allowing it to be driven after a puncture. Then there are others with an inner ring of rubber or some other type of material that serves as support. This ring sits inside the wheel and helps support the weight of the vehicle if the tire is punctured; it essentially rests on this structure.
It is recommended that Run Fat tires be fitted to a tire type called EH2 (Extended Hump), which acts as a non-slip block between the metal and rubber when the tire is at zero inflation pressure. Standard wheels are known as H2, and can be fitted with run-flat tires, but do not guarantee the same safety standard.
Since they continue to operate even though they lose pressure, all run-flat tires can only be used in a vehicle equipped with a Tire Pressure Monitoring System (TPMS). The TPMS alerts the driver when one of his tires starts to lose air. Without it, you may not be able to tell when you’re rolling with a flat tire.
Warning: Never attempt to repair a run-flat tire. It’s a sacrifice kit. It is designed to cover a limited distance and not a single tire manufacturer recommends repairing it. You can’t inflate a flat tire once it’s punctured.
You can drive with a flat tire. The main benefit of a run-flat tire is being able to circulate without air in the tube. You don’t have to get out of the car in the cold, either because of the rain, or on a busy road. As in the world of medicine, read the instructions on this tire and consult your dealer.
Better stability after a blowout: Sudden deflation or perforation can drastically destabilize a car. Because this tire can withstand the weight and momentum of the vehicle without air, the direction and dynamics of the car will not change as drastically.
Lower vehicle weight: Without a spare tire and the repair tools to replace it, the weight of the car is theoretically reduced. However, the weight loss in the luggage compartment is compensated by the weight gain per run-flat tire due to its reinforced structure. That said, the elimination of the spare wheel allows engineers to reallocate space for some other purpose, such as increasing interior space.
As well as increasing the useful space of the vehicle, cars equipped with run-flat tires do not have a spare wheel, jack or tools.
They can increase tread wear. A 2013 study by JD Power found that, in North America, people replaced their run-flat tires an average of 9,500 kilometers earlier than owners of conventional tires.
Manufacturers place a softer compound on the tread to maximize grip and comfort. The side effect of this design results in a shortened tread life. However, at present, there should not be a marked difference with conventional tires.
Blowouts are still possible. If a driver does not heed the warnings on the dashboard and drives more than the agreed mileage or above the recommended speed, the tire may begin to disintegrate, with the same destabilizing effects. In addition, if the puncture occurred on the sidewall or the tire hit a bulky object, the driver would have to call a crane.
It’s hard to tell if there’s too little air. Another side effect of a stiffer construction is that the sidewalls do not widen if the air pressure is low. It is therefore essential to have a tire pressure monitoring system and to check the pressure frequently. Otherwise, you would never know you have a puncture.
Price: run-flat tires are more expensive to replace. Prices will vary depending on the type and location of purchase, but it is not uncommon to pay a bill of 90 or more than 100 euros for these types of tires. That’s not counting the tire.
They are heavier and less efficient. Their greater rigidity leads to an increase in mass compared to conventional tires and the average fuel consumption is between 1 and 2%, both on the road and in the city.
What is the service life of a run-flat tire?
We have just read that, conditioned by the search for comfort and resistance, the tread of a run-flat tire is more likely to wear out than its conventional equivalent. That was a fact, until recently. Progress in tire development has led to tires that will be little different from their simpler counterparts.
In general, run-flat tires use the same rubber compounds as conventional wheels, so you can expect similar longevity. Despite their reinforced components, the tread wears at the same rate as standard tires and requires the same level of care and maintenance. Keeping the wheels at their optimum pressure and checking them often will help increase their life before they have to be replaced.
Is a run-flat tire worth it?
The first question that comes to mind is when it comes to price. Are they expensive? In a word, yes. Because run-flat tires are not widely used, they tend to be more expensive than normal tires and can only be installed on certain cars. It combines that with the fact that they can’t be repaired, and they won’t make much sense to most drivers.
There is no doubt that run-flat tires are more expensive than conventional tires (from around 90 euros), and it is clear that they offer a much safer option for traffic. With these shoes on your car, the chances of reducing a puncture accident is reduced to almost zero, as they offer more reaction time to the driver. If the manufacturer allows it to be repaired and we are regular drivers, it can be a good alternative.