What are Run Flat Tires?

Experiencing a flat tire is a nightmare scenario for just about every motorist.

The inconvenience, dangers, anxiety and panic – there’s never a good time, and one never feels quite prepared to deal with a tire puncture and flat. And even though nearly all modern cars are equipped with either a spare wheel + tire or a flat tire repair (mobility) kit, managing either process is not something that everyone has the know-how and capability to do. Not to mention, roadside tire repairs are quite dangerous even for the mechanically inclined – there’s the threat of ongoing traffic, jacking up the vehicle on imperfect, uneven ground, and other serious hazards.

Run flat tires guard against the flat tire scenario by counteracting tire punctures and damage that would flatten standard tires and disable a vehicle. Instead of a roadside repair, run flat tires keep the vehicle operational, and in most cases, capable of reaching home or the nearest service station.

Here’s the need to know on run flat tires.

What are they and how do they work?

It might sound obvious (at least we think so), but conventional automotive tires require proper inflation and air pressure to function. In the case of a puncture, or other tire damage that causes a loss of air pressure, the tire becomes flat and non-operational.

Run flat tires also require air pressure for proper (full) function; however, their unique construction includes a “backup plan.”

Run flat tires “are designed to resist the effects of deflation when punctured, and to enable the vehicle to continue to be driven at reduced speeds and for limited distances.” - MichelinMan.com

Unlike in the case of a loss of air pressure with a standard tire, run flat tires don’t become conventionally flat. Even in a complete loss of air pressure situation, the reinforced construction of a run flat tire keeps the tire sidewall upright and the tire capable of rolling. The tire sidewall of a run flat tire is capable of supporting the vehicle’s weight even without any air pressure.

A run flat tire without air pressure.

How long can a run flat keep rolling after losing air pressure? Typically up to about 50 miles at a maximum speed of 50 mph. However, depending upon the severity of the tire damage, the maximum speed and/or possible distance may be reduced.

Run flat tires have the added benefit of guarding against dangerous tire blowouts. Every year blowouts cause thousands of accidents, and hundreds of motorists are injured or killed as a result. Run flat tires are probably most known for how they protect against the typical tire puncture and gradual loss of air pressure, but the reinforced tire sidewalls can also help to keep the vehicle stable and under control in the event of a sudden tire blowout, and immediate loss of pressure.

Pirelli Run Flat with reinforced sidewalls

Alternative run flat technology

The reinforced sidewall construction has been at the core of run flat technology for decades, but Pirelli has recently introduced an alternative technology called Seal Inside.

“Pirelli’s Seal-Inside Technology is the new concept of extended mobility that allows you to continue to drive your car safely in case of a puncture.” - Pirelli.com

While not technically a run flat tire that stays functional without any air pressure, Pirelli suggests the new self-sealing technology effectively counteracts 85% of the possible causes of flat tires.

Instead of allowing for a complete loss of pressure and vehicle load transfer onto the reinforced tire sidewall, Seal Inside forms a seal around any foreign object that has punctured the tire, and maintains tire air pressure keeping you mobile.

There are disadvantages

Alternative mobility technologies like Pirelli’s Seal Inside are welcome because despite their many advantages, run flat tires aren’t all positives with no downsides.

Some of the disadvantages include:

  • Harsher ride. A conventional tire sidewall is a source of ride compliance and comfort. The heavily reinforced, stiffened tire sidewall characteristic of run flat tires tends to result in more bumps and road imperfections reaching the vehicle cabin.
  • Run flat tires are a one-shot deal. If you’ve experienced a puncture and called upon the run flat technology to keep you mobile, there’s typically no reusing that particular tire. Other than in the case of severe damage, conventional tires can be repaired after a puncture and loss of air pressure. With run flat tires, even if the puncture is repairable, the structure of the tire may be considered compromised once it’s been used in the run flat capacity (driven on with no air pressure). This means that instead of the nominal fee associated with patching a tire, you’re looking at the expense of an entirely new tire.
  • Higher cost. Run flat tires are generally more costly than conventional tires. While the premium associated with run flat technology has lessened over the years, most run flat tires remain more expensive than standard alternatives, compared to the same type of tire from the same brand.
  • Limited selection. For any given vehicle there are likely many more non-run flat tires that are a fit, which means a greater potential for matching the tires to your vehicle and unique driving circumstances. A prioritization of run flat technology could mean that other tire needs are not fully addressed.

How do I find run flat tires for my vehicle?

If you decide the disadvantages of run flat tires don’t outweigh the strong advantages and safety benefits, you’re not alone. Luxury carmakers often fit run flat tires as Original Equipment (OE) tires, and especially after experiencing a flat tire situation, many motorists have chosen to replace their conventional tires with run flats.

Run flat tires are often immediately identifiable by a run flat designation at the end of the tire name, which varies by tire manufacturer. Examples include:

  • “ZP” (Michelin) e.g., Michelin Pilot Super Sport ZP
  • “RFT” or “Run Flat” (Pirelli) e.g., Pirelli Cinturato P7 All Season Run Flat
  • “SSR” (Continental) e.g., Continental ContiProContact SSR
  • “XRP” (Kumho) e.g., Kumho MX XRP

A search for run flat tires is very straightforward on TireBuyer. After entering in your vehicle details or tire sizes, use the “Refine Search” menu on the left side of the page. Scroll down to “Run Flat” and select the “Yes” checkbox. This action will refine the tire results to include only run flat tire options.

If you want to discuss the pros and cons, or explore run flat tire options for your vehicle, give our customer service experts a call at 866-961-8668.