How Exactly Does A Run Flat Tire Work?

For car enthusiasts, tires are more than just rubber hoops — they're the final link between machine and tarmac. (Here's a list of the best tires for your car, SUV or truck.) Among the many technologies vying for attention in the modern tire world, run-flats spark some of the most polarized debates.

At the core of a run-flat tire's function is its ability to support a vehicle even after losing air pressure — a feat accomplished by structurally reinforced sidewalls. Unlike conventional tires that collapse under the vehicle's weight when deflated, run-flats use robust rubber compounds and thicker sidewall architecture to bear the load for limited distances. The most common systems — self-supporting run-flats — can typically operate for 50 miles at up to 50 miles per hour post-puncture, letting drivers safely limp to a tire shop without busting out a jack on the shoulder of the road.

Enthusiasts might recognize three main run-flat technologies: self-sealing, self-supporting and auxiliary-supported. Auxiliary support includes internal support rings like Michelin's PAX system, while the most common examples of run-flats — often found on premium vehicle brands — rely on self-supporting sidewall technology. The first, self-sealing, is built to attend to tread punctures immediately thanks to tire sealant added as an extra lining inside the tire.

The biggest advantage of run-flat tires is peace of mind. In the event of a puncture, you don't have to pull over immediately — you can keep driving to a nearby repair shop, avoiding roadside hazards or the need for a spare tire. Many premium automakers have adopted them as standard equipment in vehicles without a spare.

However, the downside lies in the stiff sidewalls, which can make the ride noticeably firmer. Enthusiasts often criticize the reduced compliance over potholes and less precise road feedback, especially on sports sedans and coupes. Run-flat tires are also more expensive than their conventional counterparts — they often sell for $40 to $65 more than conventional tires — and they're not always repairable after a puncture. 

Drivers looking to push their performance car like the BMW M3 often replace original-equipment run-flats with sticky rubber from Michelin Pilot Sport line — which doesn't come in a run-flat variant. (Here's why new tires have all those little tiny hairs.)

For manufacturers, it's a tidy solution: no need to carve out space for a spare tire, and a safer, more consistent product for everyday drivers. But for the driving enthusiast, the calculus shifts. Performance driving demands grip, communication, and consistency — three things run-flats tend to compromise compared to traditional summer or ultra-high-performance tires.

For a daily driver where spirited driving is limited to highway ramps or the occasional backroad, run-flats might make sense. They offer real-world security and convenience. But if your weekends include autocross, canyon carving, or track sessions, they're probably holding your chassis back. The weight, stiffness, and tread-compound compromises simply can't keep up with a well-sorted set of Michelin PS4S or Bridgestone Potenza RE-71RS tires.

There's also the matter of availability. Not all tire shops carry run-flats, especially in less populated areas, and options can be severely limited in niche sizing. If you're rocking staggered 19s or ultra-low-profile setups, you'll likely find more choice (and better value) by switching to conventional tires and keeping a mobility kit or compact spare in the trunk.