Before committing to run flat tyres, it’s best to read up on how to use them because they can sometimes do more harm than good. Keep reading to find out why and when it’s worth using this technology.

A nail stuck in the tyre

Run flat tyres - what are they?

The history of run flat tyres begins before the second World War. A dynamic development of this technology took place during the war, and further work was carried out in the years after. On a wider scale, this solution has been used in passenger cars since the late 1980s.

Run flat tyres are still gaining in popularity. Most of them allow you to drive around 50 miles at 50 mph (although there are other options) after puncturing your tyre. They can be manufactured with three main methods.

Is it worth buying run flat tyres?

If you're thinking about buying run flat tyres, it's a good idea to look at the advantages and disadvantages of them prior to buying.

AdvantagesDisadvantages    

safety (no risk of losing control of the vehicle after a sudden puncture)		higher price and weight of the tyre
no need to replace the wheel immediately (e.g. in a hazardous area)less comfortable (bumpy and louder)
more space in the boot (no need for a spare wheel)the tyres are more rigid and wear out faster
greater resistance to mechanical damage (e.g. when driving into a hole or hitting a kerb)can't be fixed in every garage
protection against theft of a car on the wheel - if someone tries to stop a car with Run Flat tyres by signalling an alleged puncture, the driver knows that it is an attempt to steal the carsome models can’t be repaired after puncturing and need to be replaced

occurrence of false tyre pressure sensor readings

The table above shows that run flat tyres have more disadvantages than advantages. However, when you look into it further, you can see that they are only really minor disadvantages. Obviously, there are higher operating costs (the price, faster wear and tear, more difficult installation). However, the main advantage is that the risk of a tyre blowout after a puncture is practically zero, which means that both the driver and passengers will be safer. 

Run flat tyres are often fitted on high performance luxury cars. Owners of such cars sometimes drive faster as their cars can achieve higher speeds than ordinary vehicles. It's not hard to imagine what would happen if ordinary tyres were punctured and you lost control of your car at a speed well over 80 mph - and still only very few drivers know how to react to a tyre burst while driving.

A puncture in a run flat tyre is hard to spot and the fastest way to detect it, is through the wheel pressure control system.

Run flat tyre pressure

You will find all the necessary tips on how to properly use a car with run flat tyres in its owner’s manual. For example, you can inflate such tyres with nitrogen, but not all manufacturers allow the use of products designed to seal small punctures. As with standard tyres, the best possible solution is to maintain the tyre pressure at the level recommended by the manufacturer.

When to use run flat tyres?

  1. The car on which the run flat tyres are fitted to must have working wheel air pressure sensors. Without them, you won’t know that there is a problem. 
  2. Cars with run flat tyres should be specially adapted to them. In this case, suspension components (e.g. BMW with softer suspension settings) and power steering systems (ABS, stability systems) are designed and calibrated to work exclusively with this type of tyre. Fitting ordinary run flat tyres will result in unpredictable performance at high speeds.
  3. Run flat tyres should only be fitted by professional tyre repair shops. Fitting them on a normal mount usually results in damage to the side or bead of the tyre. This can result in an unexpected blowout at high speeds, which in turn can result in a serious accident. 
  4. It is assumed that run flat tyres can cover a distance of approximately 50 miles (80 kilometers) after a puncture at a speed not exceeding 50 mph (80 km/h). It’s worth remembering that these are average values. It’s not always possible to take advantage of the full potential of this technology. 
  5. Run flat tyre manufacturers advise against exceeding the maximum speed these tyres can be used at. In exceptional circumstances, however, they can withstand much more. At low temperatures, when the speed is reduced to 50 km/h, the range of these tyres can increase by at least 50% compared to " standard " conditions. 
  6. Some manufacturers allow the repair of punctured run flats. Please note, however, that the range of the tyre will be reduced by several kilometers when the next damage occurs. 
  7. If the pressure drops, inflate the damaged tyre as soon as possible, e.g. at the nearest petrol station. The pressure after a puncture usually should drop slowly. Inflating the wheel will reduce the risk of permanent damage to the tyre.

Symptoms of a run flat tyre puncture

  • alarm from the wheel pressure sensors,
  • an increase in the force required to turn the steering wheel (in the event of damage to the front wheel),
  •  the car pulling slightly over to the damaged tyre’s side,
  • increased noise while driving,
  • vibrations or the sensation of wheel banging at speeds above 90-100 km/h.


Winter run flat tyres

Many drivers wonder if winter run flat models are any good. Research shows that they are as well adapted to winter conditions as conventional seasonal tyres. They use the same technology as their standard counterparts. The only drawback is that winter run flat tyres have a slightly harder structure that can affect the driving comfort. However, safety parameters remain the same in most cases.

Attention!: It is very harmful for run flat tyres to heat up when driving without air after a puncture. The worst conditions are heat combined with a heavy load (e.g. whole family in the car).

Technologies used in run flat tyres

Run flat tyres are generally divided into three types: reinforced, self-sealing and with a support ring.

Technology

Description

Examples

Reinforced construction

There is a rubber insert in the sidewall of the tyre to help absorb pressure loss. The tyre bead, which is firmly attached to the rim, is also reinforced. The solutions used make the sudden loss of pressure almost imperceptible for the driver. Hence the need to use pressure sensors.

Self-sealing

Tyres have an additional sealing layer inside. In the event of a puncture, this sealing layer helps to stabilize the correct pressure level. These tyres are considerably heavier than the standard tyres (15 to 20%) sometimes having problems with balancing the wheels. Therefore, this technology has not found a wider scope for use.

  • Goodyear Dureseal (for trucks)

  • Continental ContiSeal

  • Kleber Protectis

  • Pirelli SWS (Safety Wheel System)

Support ring

This is a technology that involves the use of a special ring in the interior of the tyre. In the event of  pressure loss, the ring acts as a carrier and additionally prevents the tyre from slipping off the rim.

The individual technologies are described in detail below:

DSST – Dunlop Self-Supporting Technology

  • In use since 1998.
  • In the event of a drop in air pressure, the weight of the vehicle is transferred to the patented structure of the reinforced sidewalls of the tyre.
  • Acceleration, braking and steering are virtually unchanged when driving without air.
  • DSST tyres are suitable for mounting on standard rims after the vehicle has been fitted with an air pressure warning system (Dunlop Warnair recommended).
  • Range - up to 50 miles (80 km) at a speed of up to 50 miles per hour (80 km/h)

 EMT - Goodyear Extended Mobility Tyre

  • It's been in use since 1992.
  • In the event of a drop in air pressure, the vehicle's weight is transferred to the reinforced tyre sidewalls.
  • The vehicle should be fitted with a Tyre Pressure Monitoring System (TPMS).
  • The EMT series is only recommended for vehicles whose manufacturer has approved the EMT series as a standard or optional extra.
  • EMT tyres may be repaired in accordance with the specified conditions. However, provided that the damage has occurred on the tread surface and not on the sidewalls.
  • Range - up to 50 miles (80 km) at a speed of up to 50 miles per hour (80 km/h) (except for the extended Chevrolet Corvette).

 HRFS - Hankook RunFlat System

  • This technology was introduced in 2004.
  • The system is based on stiffened inserts on the sides of the tyres.
  • The HRFS tyre selection is limited to the most expensive luxury, sports and SUV cars.
  • Range - up to 50 miles (80 km) at a speed of up to 50 miles per hour (80 km/h)

 PAX – Michelin

  • This solution has been in use since 1999.
  • The support is a lightweight plastic insert on the rim, placed inside the tyre, carrying the full load in the event of a lack of pressure. A special bead construction prevents the tyre from separating from the rim while driving.
  • A complete wheel with a PAX system weighs on average 17 % more than a standard wheel with a tyre of the same size. The total weight of the PAX wheel set is less than five standard wheels (four plus spare).
  • Compared to tyres with stiffened sidewalls, the PAX series tyres maintain full suspension comfort under normal driving conditions and therefore do not overload the suspension and wheel rims with additional work. However, the comfort of driving gets worse when the tyre loses air.
  • PAX tyres require dedicated rims.
  • PAX provides a range of up to 125 miles (200 km) at speeds of up to 54 miles per hour (88 km/h).
  • The first cars equipped with a PAX system as standard on the European market were cars such as the: Renault Scenic (since February 2002), Audi A8 (since December 2002), Rolls-Royce Phantom (since January 2003) and Audi A4 (since September 2004).
  • The PAX system is very expensive and Michelin no longer uses it, but cars with PAX tyres can be found in the aftermarket.

RFT – Bridgestone Run Flat Tyre

  • This technology has been used since 1987
  • The technology is based on reinforced sidewalls of the tyre.
  • The first generation of RFTs includes tyres manufactured between 1987 and 2004. The most important feature of the second generation (since 2005) is the improved sidewall construction for better comfort. The third generation (since 2009) also has improved side wall cooling. 
  • Bridgestone recommends that EH2 type rims should be used in conjunction with RFT tyres, although they may also be fitted on standard rims.
  • An RFT emergency repair is permitted in the event of a puncture on the tread surface, but should be replaced as soon as possible.
  • A car with RFT tyres should be fitted with a Tyre Pressure Monitoring System (TPMS).
  • Range - up to 50 miles (80 km) at a speed of up to 50 miles per hour (80 km/h).

 RSC – BMW Runflat System Component

  • In use since 1999.
  • It's not just a tyre, it's a complete system for unpressurised driving: it consists of tyres with reinforced sides (e.g. Michelin ZP), an EH2 rim that prevents the tyre from separating from the bead when there is no pressure and an air pressure monitoring system.
  • Range - up to 93 miles (150 km) at a speed of up to 50 miles per hour (80 km/h)

 SSRF – Pirelli Self-Supporting Run Flat

  • Pirelli developed its research program in collaboration with the Goodyear team.
  • The SSRF system is based on the reinforced sidewalls of the tyres.
  • It is recommended to mount SSRF tyres on EH2 rims, however standard rims are allowed. The car must be fitted with an air pressure monitoring system (TPMS).
  • The company's debut on the market of airless tyres was the 17-inch Scorpion BK designed specifically for the off-road luxury Lamborghini LM-002, manufactured since 1986.
  • A punctured SSRF tyre should be replaced with a new one.
  • Range - up to 50 miles (80 km) at a speed of up to 50 miles per hour (80 km/h)

SSR – Continental Self-Supporting Runflat

  • This technology uses reinforced tyre sidewalls.
  • SSR tyres are suitable for most standard rims. However, the vehicle must be equipped with an air pressure monitoring system with sensors attached to the rims.
  • SSR tyres are not suitable for repair after driving with no air.
  • Range - up to 50 miles (80 km) at a speed of up to 50 miles per hour (80 km/h)

 

Run flat tyres have special reinforcements inside, which allow you to drive without air (photo: Continental).


TRF – Toyo Run Flat

  • Rigid inserts on the tyre sidewalls transfer the load in the event of a drop in air pressure.
  • The special bead construction prevents the tyre from slipping off the rim.
  • The additional layer of cord on the sides is heat-resistant.
  • The TRF is always accompanied by a tyre pressure index.
  • Range - up to 50 miles (80 km) at a speed of up to 54 miles per hour (88 km/h)

XRP – Kumho eXtended Run-Flat Performance

  • The solution has been in use since April 2006.
  • Unique bead design prevents the tyre from slipping off the rim.
  • The special rubber compound has increased heat resistance.
  • XRP tyres can be used on any passenger car.
  • Air pressure and temperature sensors are mounted on the wheel rims.
  • Range - up to 50 miles (80 km) at a speed of up to 50 miles per hour (80 km/h)

ZP – Michelin Zero Pressure

  • A solution used since 1995.
  • When the air pressure drops, the tyre rests on its stiffened sidewalls.
  • ZP tyres may only be used in cars that have been designed to work with run flat tyres and are fitted with rims dedicated to ZP. The ZP series includes Michelin Primacy HP, Pilot Sport and Pilot Alpin.
  • If more than one tyre is damaged, it is recommended to stop.
  • As a general rule, tyre repair after a flat tyre is not permitted.
  • Range - up to 50 miles (80 km) at a speed of up to 50 miles per hour (80 km/h). With tyres additionally marked "SR", the range is extended to 112 km (70 miles).

ZPS – Yokohama Zero Pressure System

  • A relatively new solution that has been available only since 2009 in the ADVAN Sport model.
  • The system uses stiffened sidewalls made of composite material to limit the temperature increase.
  • A special filler layer between the stiffener and the bead increases the comfort of driving under normal conditions and the makes sure that the tyre is seated on the rim when driving without pressure.
  • The hexagonal cross-sectional shape of the wire rod prevents the bead from slipping off the rim.
  • Air pressure sensors ("G Sensor" Vehicle Behaviour Detection System) in wheels.
  • Range - up to 50 miles (80 km) at a speed of up to 50 miles per hour (80 km/h).

 

View our range of Run Flat Tyres

 

History of run flat tyres

Pre-war beginnings

1934 - Goodyear introduces the LifeGuard technology to the market. An additional nylon inner tube was put in the middle of a normal inner tube. In the event of a blowout or puncture, the tyre could briefly take over the entire load. The system prevented sudden air pressure drops that could result in an accident, but you couldn't get too far on such a tyre. The extra inner tube gradually released air, giving only enough time to find a safe place to replace the wheel.

War drives the progress further

1941 - The U.S. Department of Defense announces a competition for U.S. manufacturers to develop a tyre that is capable of continuing to run after being blown out for at least 75 miles (120 km). Previous French and German solutions - models filled with rubber foam - did well in times of battle, with little driving and a lot of shooting. 

Unfortunately, they needed to be thrown away after a few hundreds of kilometres of regular use. The idea of tyres with reinforced sidewalls from Great Britain, on the other hand, allowed them to cover up to 50 miles (80 km) without air.

December 1941 - The final of the competition, "Tamiami Trail", takes place on the road connecting Miami and Tampa (Florida) and runs through the Everglade marshes. The test results were poor. The best tyre only lasted 22 miles (35 km). However, the designers' work wasn’t wasted. 

By testing new materials for sidewall reinforcement, at the end of the war the Americans had managed to achieve a maximum airless mileage of 150 miles (240 km) in military tyres, where the production costs of the model were not a major factor. General Patton owed part of his rapid march from France to Germany to the innovative tyres, which are now also used in many modern military vehicles.

Dynamic development

1955 - Goodyear introduces a tyre with a Captive Air Shield made of plastic to support the load in the event of a loss of air pressure. It offers a safe range of up to 100 miles (160 km) at speeds of up to 50 mph (80 km/h). The Double Eagle models with optional LifeGuard Safety Spare inserts were advertised as "fitted with a built-in spare wheel" a few years later. Their popularity was limited by the high price.

1958 - Chrysler offers tyres with reinforced sidewalls that are capable of running short distances without air.

1965 - NASCAR formula cars are fitted with Goodyear engineers' Lifeguard Racing Shield tyres. The system has been used successfully to this day.

October 1973 - The Austrian company Polyair (a tycoon in the production of pneumatic cushions for trucks today) presented a tyre with stiffened sidewalls made of an innovative type of polyurethane, which was flexible like rubber, but remained 4 times more resistant to wear. The Polyair proposal was 1/3 lighter than the traditional one, and thanks to the very high strength of the compound it was simpler to build, without layers of cord and warp. 

It was capable of carrying on after without air over a distance of up to 60 miles (100 km) at a speed of up to 43 mph (70 km/h). The model heated up much slower and less than the tyre made of synthetic rubber, thanks to a significant reduction in the mid-molecular friction of the new compound. The initial disadvantage was its poor grip on wet roads.

1978 - Goodyear introduces the SST (Self Supporting Tyre) tyre with a reinforced sidewall to carry the pressure drop load. It was similar to what we use today. It could carry on for 40 miles (64 km) at up to 40 mph (64 km/h).

Run flats today

1987 - The Porsche 959 was the first car to be fitted with run flat tyres as standard (Bridgestone RE71). Since the mid-1980s, Bridgestone’s 175/70 R13 run flat tyres have been part of the package when you buy a new Honda Civic. They allowed you to travel up to 60 miles (100 km) at a speed of up to 37 mph (60 km/h).

1997 - Goodyear Eagle F1 GS-EMT Run Flat Flat tyres become a standard on the Chevrolet Corvette, providing a pressureless range of 200 miles (320km) at up to 54 mph (88 km/h) at 22°C.

April 1998 - Michelin presents the PAX system.

December 1999 - The Z8 Roadster is the first BMW to be fitted as standard with an RSC system (dedicated EH2 rims, run flat tyres and air pressure sensors).