Run-Flat Tires: Pros and Cons

What a run-flat tire is

A run-flat tire is built to keep supporting the vehicle for a short time after it loses some or all of its air. The industry association USTMA describes the goal as letting you drive a limited distance, at reduced speed, after a puncture or other pressure loss.

The most common type is self-supporting. Trade press describes these as using stiffer, tougher sidewall rubber that can carry the vehicle's weight at low or zero pressure. A second design uses a support ring inside the tire, mounted on a special rim.

You can usually spot a run-flat by a marking after the size on the sidewall. USTMA lists 'RF', 'RunFlat' and 'Extended Mobility' as examples.

What you can and cannot do after pressure loss

Run-flats are for limited service. USTMA says the speed and distance must be limited according to the tire and vehicle makers' recommendations.

It adds that they are usually limited to no more than 50 mph and no more than 100 miles, and that the restrictions vary by product and application. The 2022 Ram 2500/3500 owner's manual, for example, gives 50 miles at 50 mph for that vehicle. The right number for you is in your owner's manual.

Treat the limit as a ceiling, not a target. USTMA says driving the shortest distance at the lowest possible speed may improve the chance that the tire can go back into service.

Handling changes when a tire loses pressure, especially in corners. USTMA advises avoiding hard cornering and hard braking. If you feel unusual vibration or handling trouble, release the accelerator, slow down gradually and stop as soon as you reasonably can.

Operating past the recommended limits can lead to sudden tire destruction, according to USTMA. After a tire has been run low or flat, it should not be touched right away because it may be very hot.

The pros

You may not have to stop at the roadside

USTMA's own wording is that run-flats let drivers avoid stopping to change a tire or restore and re-inflate it in an oftentimes dangerous location at the side of the road. You can drive on to a service location instead, within the limits above.

Some vehicles are designed without a spare

Vehicles that come with run-flats may not carry a spare tire. Your owner's manual shows what your vehicle has. USTMA notes that if you replace run-flats with conventional tires, you may need to acquire a spare, a jack and a lug wrench, or a sealant-based kit to keep any emergency mobility.

The cons

They require a working TPMS

Because a run-flat can keep going without air, you may not notice a problem. USTMA says a functioning tire pressure monitoring system must be used with run-flats to warn you when a tire is running underinflated. If your vehicle was not built with TPMS, USTMA says one has to be retrofitted before you fit run-flats.

You still need a gauge

TPMS does not replace manual checks. USTMA says to check pressure with a gauge at least monthly and before every long trip, using the pressure on the door placard or in the owner's manual.

Repair is limited

USTMA says no tire is indestructible, and run-flats can be rendered unusable by a puncture or by being run in low or zero-inflation mode. Some, but not all, tread-area punctures may be repaired under specific procedures. Some run-flats must be replaced after low or zero-inflation operation.

Once a tire has been run low or flat, USTMA says it must be removed from the wheel and inspected by a tire service professional. That inspection decides whether it can be repaired or must be replaced. The 2022 Ram 2500/3500 owner's manual states that a run-flat tire is not repairable.

Ride and cost can differ from a regular tire

A 2016 Tire Review article said the stiff sidewalls of a self-supporting run-flat result in a harsher ride. It also said run-flats cost one-third more on average than conventional tires.

That is a 2016 figure, and ride and price vary by tire and vehicle. Ask your installer for current specifics.

Replacement rules are stricter

USTMA recommends replacing all four run-flats at the same time with four run-flats when they wear out. It says never to mix run-flats with conventional tires except in an emergency on a limited, temporary basis. It also advises against mixing different run-flat technologies.

If you buy a replacement, the wheels must be compatible too. USTMA notes that some manufacturers require special rims, such as extended-hump rim contours, and that sensors must be compatible.

Switching between run-flat and regular tires

From run-flat to regular

USTMA recommends run-flats be replaced with run-flats. If you want regular tires instead, it says to consult the vehicle and tire makers first. It lists these consequences:

• You lose run-flat capability, and emergency mobility is negated unless you carry other equipment.
• TPMS displays, alarms and logic designed for run-flat operation may be affected.
• Handling, stability and performance may be affected.
• The owner's manual references to run-flat fitment may no longer apply.

From regular to run-flat

USTMA says run-flats may be acceptable replacements for conventional tires, depending on the tire, vehicle, wheel and TPMS. It also says a vehicle or tire maker may advise against certain run-flats on vehicles that did not originally have them. The vehicle must have an operational TPMS, and the wheels must suit the tire.

A run-flat uses the same inflation pressure as a conventional tire with the same size code, load index and speed rating, per USTMA.

What a run-flat means for your warranty

Warranty terms differ, but they can include run-flat specific conditions. Bridgestone's 2019 US warranty manual lists exceeding the run-flat speed or distance limits as an exclusion. It also says run-flat adjustments are made only at certified run-flat retailers.

Choosing: a short checklist

Use these questions when you compare options.

• What does my owner's manual say about run-flat tires, and what are its limits?
• Does my vehicle have a working TPMS that the replacement tires will work with?
• If I pick a regular tire, how will I handle a flat?
• Will the shop repair a punctured run-flat, or replace it?
• Do my wheels and sensors suit the tire?

Run-flats come in the same size designations as regular tires. If you want to compare a different size, use the tire size calculator. To search sizes, use the tire finder, and confirm the size on your sidewall or the driver's door placard before you buy.