Holding back yourself from going off-road as you don’t want to end up with a flat tire? Run-flat tires can be the ultimate solution to this issue as they can easily run for 50 miles or more when punctured. But what happens when your run-flat tire goes flat? Can you put air in a run-flat tire?
Yes, you can put air in a run-flat tire. Use a tire inflator or air compressor to put air in run-flats. A manual floor pump like bicycle pumps will work too. Also, your vehicle might come with a repair kit carrying all the necessary tools to inflate run flats in cases of emergencies.
However, you must use a pressure gauge to check the PSI level as run-flats are stiffer than regular tires which makes it impossible to detect visually whether the tire is properly inflated or not. Let’s dive deep and find out everything you need to know about run-flat tires.
What Are Run Flats?
As the name suggests, run-flat tires allow you to keep driving safely even when the tire is flat. The unique design of run flats includes a reinforced sidewall with a steel belt or support rings made of thick rubber.
Consequently, the sidewalls don’t fold when the air pressure decreases due to puncture and the wheel rims of your vehicle remain unharmed. It allows you to drive up to a certain distance giving you sufficient time to find a garage or tire repair shop.
In the United States, around 15% of modern cars feature run-flat tires to reduce the weight of a spare tire and make the vehicle more spacious.
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How to Tell If Tire Is Run Flat?
Checking out the sidewall of the tyre is the easiest way to tell if it’s a run-flat. Different brands use different logos to mark their run-flat tyres. Here are some run-flat markings for most popular tyre brands:
- Goodyear: ROF (short for Run On Flat) / EMT (short for Extended Mobility Technology)
- Continental: SSR (short for Self-Supporting Run-Flat)
- Dunlop: DSST (short for Self-Supporting Run-Flat)
- Michelin: ZP (short for Zero Pressure)
- Pirelli: Run Flat
- Bridgestone: RFT (short for Run Flat Technology) / DriveGuard
- Hankook: HRS (short for Hankook Runflat System)
How do run flats work?
Now it’s time to find out how the magic of run-flat tires happens. Although different manufacturers use different materials and technologies, most run flats fall into two main categories. Here’s how they work-
- Self-Supporting Run-Flat Tires
This type of run-flat comes with Flat Resistance Technology (FRC) and reinforced thick sidewalls. While regular tyres have 1/8″ sidewalls, run flats feature 3/4″ reinforced sidewalls.
The FRC includes a steel belt with foam fillings inside the wheel spine. It prevents the sidewall and tire tread of a flat tire from creasing when the tire gets punctured. Therefore, you can safely drive your vehicle without worrying about additional damage.
- Support Ring System Run-Flat Tires
In regular tires, the weight of the vehicle is carried by the air pressure of the wheels while driving. When you experience a flat tire, such tires lose air pressure. As the wheels alone can’t carry your vehicle’s weight, you can’t drive with flat regular tyres.
To solve this issue, some manufacturers incorporate strong rubber rings in the wheel structure allowing it to safely carry the car’s weight when there’s little to no air pressure. And that’s how run-flat tyres can survive some extra miles with a puncture or low air pressure.
Can You Put Air In A Run-Flat Tire?
Yes, you can put air in a run-flat tire just the way you put air in regular tires. For this, you have three choices given below:
- Air Dispenser
Most gas stations have air dispensers on their outskirts for inflating any type of tire including run flats. You can park your car in a nearby gas station and spend a few cents to a dollar for putting air into your run-flat tire.
- Automatic Air Compressor
Although this tool is expensive, using an automatic air compressor is probably the best option to put air into your run flats. That’s because you can carry the tool anywhere and inflate your run-flat tire free of cost whenever you want.
Also, it doesn’t take much physical effort to run the tool. However, you’ll need a power outlet to switch on the automatic air compressor.
- Manual Floor Pump
If you want something cheap and portable, using a manual floor pump can be an option. Bicycle pumps will work with run-flats, but it takes a lot of physical effort to inflate car tyres with such manual tools. So, we recommend using it when you want to put only a small amount of air to reach the standard PSI level.
Remember, you must choose a Schrader-valve-compatible bicycle pump for this job.
How many miles do run-flat tires last?
In general, run-flat tires can last 30,000 to 70,000 miles given that the tire isn’t damaged or punctured. With proper maintenance and less frequent use, run flats can last 3 to 5 years. But, how long do run flat tires last when it goes flat?
As for deflated or punctured run-flat tires, they can survive up to 50 to 100 miles at 50mph or lower speed. The numbers vary depending on the tire brand, maintenance routine, and usage of the tyre.
Do Run-Flat Tires Need Air?
Yes, run-flat tires need air to carry the weight of the vehicle while driving. Without air or air pressure, it can only support the vehicle’s weight for a certain distance (50 miles or less), thanks to the reinforced rubber sidewall.
Run-flat technology requires air just like any regular tire to create sufficient air pressure that supports the vehicle’s full weight. The strengthened sidewalls alone can’t carry the vehicle for long. So, maintaining a standard air pressure level is must for run-flat tires.
How to Tell If Run-Flat Tire Is Punctured?
As run-flats are thicker than regular tires, it can be a bit difficult to detect a puncture. However, the following instructions might help in this case. Let’s have a look.
Warning Light Tuned On
If your vehicle came with factory installed run flats, it will have a Tire Pressure Monitoring System or TPMS. When the air pressure of your tire lowers, the TPMS turns on and you’ll notice a warning light or alerting message on your dashboard’s computer screen.
Common Damage Signs
Just like any other standard tire, run flats might also display some common signs of damage. For example, you might hear a muffled sound if the car gets punctured while driving.
When you visually inspect the tires, there will be noticeable damage or wear to the rubber. Besides, you’ll hear a hissing sound of leaking air. These are the common indications of puncture in run-flat tires.
Low Air Pressure
Want to be fully sure if your run-flat is punctured? Use a pressure gauge to measure the air pressure of the tyre. Typically, the air pressure of a standard run-flat is 30 to 35 Psi. If the measured air pressure is excessively lower than this level, the tyre is punctured.
Be sure to check the air pressure while the tires are cold as high temperature can mess with the readings.
What to Do When Run Flat Tires Go Flat?
Even your run-flat tires can go flat due to a puncture or other damage. In this case, you can either keep driving or put air to inflate the tire. Here are the details-
> Keep Driving
As run-flats are designed to safely run for about 50 miles when flat, you can keep on driving to reach home or a repair shop. You must maintain the manufacturer-recommended mileage to avoid damaging your wheels. Most manufacturers recommend driving at 30mph- 50mph.
> Put Air in Run-Flat Tires Using Air Dispenser
- Find a gas station with an air dispenser. Place your vehicle near the dispenser so that its hose can easily reach your tire valve. Put coins to start the machine and remove the stem cap on your car’s wheel valve.
- Connect the air hose to the wheel valve and put air until the tire is inflated. If you hear a hissing sound of passing air, the fit isn’t correct. Attach the hose to the valve snugly so that no air can pass.
- To check if the tire is correctly inflated, place a pressure gauge on the tire valve and wait for a few seconds. The reading will be shown on the gauge screen. You can find the standard PSI level for your vehicle on a sticker placed on the driver’s side door jamb. Or, refer to your owner’s manual.
> Put Air in Run-Flat Tires Using Air Compressor
- If you want to fix your flat tire at home, a home automatic air compressor will be a good choice. You’ll need a power outlet to turn on the device. So, plug it into the 12V power outlet of your car. After that, remove the cap from the rubber valve stem of your car wheel.
- The air compressor has a hose that needs to be connected to the car valve. Make sure it fits snugly to prevent air from leaking. Turn on the air compressor switch to put air in your run flats.
- As the air compressor comes with a pressure gauge, you can easily check the PSI level. Although the readings aren’t always accurate, use it to get an overall idea of how long you should keep putting air.
- When you’ve reached the standard PSI level for your car, disconnect the hose from the valve and put the cap back on.
Can Run-Flat Tires be Plugged?
It depends on the damage type and the manufacturer’s recommendation. A tire plug is used to patch punctures and other similar damages of regular tires. Plugging a damaged tire is a widely used method of tire repairing. Although it will work on a run-flat tire, the question is whether you should repair a run-flat tire or not.
According to the USTMA or U.S. Tire Manufacturers Association, you should consult a trained technician for repairs. Besides, the damage should be not be anywhere other than the tread area. Also, if the puncture injury is greater than 6mm or 1/4 inch in diameter, you shouldn’t repair the tire. These guidelines will be applied to run-flat tires as well.
So, what do the manufacturers say about plugging or repairing flat tires? Some manufactures allow repairing their run flats while some don’t. Brands like Bridgestone, Dunlop/Goodyear, Hankook allow repairing their run-flats by expert mechanics. Michelin allows only one repair whereas Pirelli and Continental completely prohibitfrom repairing their run flats.
In any case, you should plug your run-flat tire only as a temporary fix. Replacing the damaged tires is the best option.
Frequently Asked Questions (FAQs)
1. When to Replace Run-Flat Tires?
You should replace your old run flats with new ones once it has passed the 30,000-70,000 miles range. The range will vary depending on the brand, so refer to your owner manual for the exact number. Typically, you should change run flats after 10 years.
Also, if there’s any puncture or noticeable damage to the sidewall and the tire has too many repairs, you should replace it as soon as possible.
2. Can you use Fix-a-Flat on run-flat tires?
No, the manufacturers of Fix-a Flat don’t recommend using it on run flats. That’s because run flats aren’t designed to accept sealants like fixing a flat. Besides,
Fix-a Flat is a liquid sealant. So, if the tyre has foam inserts, it will be soaked into the foam instead of sitting on the surface and sealing the puncture.
3. How long do Pirelli run-flat tires last?
Although Pirelli run-flat tires don’t come with specific warranty, they can last 30,000 to 40,000 miles. It can last up to 50 miles at 50mph with a puncture. However, the manufacturers recommend that you must replace the punctured or flat tire instead of repairing it.
4. Does Audi use run-flat tires?
Yes, many recent models of Audi passenger cars and SUVs come with run-flat tires. According to the manufacturer, Audi run-flats can survive up to 30km at 80km/h mileage with low air pressure.
5. Are run-flat tires worth it?
No, most users don’t think run-flat tires are worth the cost. Run flats are noisy and bumpy which makes it impossible to enjoy a comfortable ride. Some users also reported handling and mileage issues. Moreover, once damaged, you need to replace the tire with a new one which is very costly. So, run-flats aren’t worth the hassle.
To put air in your run-flat tire, head over to a gas station with air dispenser. This is the easiest and lowest-cost option to put air in your run flats. Remember, if your run-flat tire goes flat, you shouldn’t drive with it for more than 50 miles.
Otherwise, you might end up damaging the wheel rims.
Certification: BSc in Mechanical Engineering
Education: Mechanical engineer
Lives In: 539 W Commerce St, Dallas, TX 75208, USA
Rasel is an auto mechanic student and writer with over half a decade of experience in the automotive field. He has worked with top automotive brands such as Lexus, Quantum, and also owns two automotive blogs autocarneed.com and taxiwiz.com.