Emergency running systems

Introduction 

Tires with emergency running characteristics can still be used for a certain distance even if they suffer a complete loss of pressure. There are two different systems which meet these requirements:

• emergency running system with self-supporting tires
• emergency running system with integrated support ring

Emergency running systems setup 

Emergency running system with self-supporting tires 

The side walls of the self-supporting tire are reinforced. In conjunction with a special disc wheel, the tire can still be used for a certain distance even if it suffers a complete loss of pressure.

Mobility is retained for the following distances up to a speed of 80 km/h (50 mph) and with a cautious, suitably adapted driving style:

Self-supporting tires demand permanent monitoring of the tire pressure to ensure that the driver is given adequate warning if pressure is lost during a journey. For this reason, these tires are only available in conjunction with the warning system RDW and from 03/2000 also with RDC.

To prevent the self-supporting tires from becoming detached from the disc wheel in the event of a complete loss of tire pressure, they must be fitted to newly developed wheels with modified disc wheel humps, but with unchanged tire seating (= standard disc wheel).

However, the new wheels can also be used for standard tires of the same size.

Comparison standard tires / self-supporting tires 

Standard tires, unpressurized 

Fig 1: Identifying Standard Tires - Unpressurized

Courtesy of BMW OF NORTH AMERICA, INC.

Self-supporting tires, unpressurized 

Envulcanized reinforcement (1) made of a temperature-resistant rubber compound.

Fig 2: Identifying Envulcanized Reinforcement

Courtesy of BMW OF NORTH AMERICA, INC.

Disc wheels 

H2 disc wheel (standard disc wheel) for emergency running system with integrated support ring 

1. Hump 2 of standard disc wheel
   Fig 3: Identifying Hump Of Standard Disc Wheel

   Courtesy of BMW OF NORTH AMERICA, INC.

EH2 disc wheel for emergency running system with self-supporting tire 

1. Extended Hump 2 of disc wheel
2. Drop center relocated a few millimeters to the center (pre-centering on outside)
   Fig 4: Identifying Extended Hump Of Disc Wheel

   Courtesy of BMW OF NORTH AMERICA, INC.

Example: from current 1.1 bar to 0.6 bar (X5 or Landrover disc wheel)

Emergency running system with integrated support ring 

(In the future, primarily on heavy safety vehicles)

The support ring is made of a high-strength resilient plastic and is fitted on the disc wheel inside the tire. The support ring can only be removed using special tools which have been specially approved by BMW. It can only be removed after destroying the tire.

Emergency running systems with integrated support ring are used in particular on heavy safety vehicles. They allow the vehicle to be driven away from a potential danger without dropping speed even if the tires have suffered a complete loss of pressure (flight situation).

It is possible as an option to have the tire pressure monitored by an RDC system. The RDC is installed by pressing the components into the support ring before it is fitted.

Wheel structure with integrated support ring 

Emergency running system with integrated support ring 

1. Tire
2. Support ring
   Fig 5: Identifying Emergency Running System With Integrated Support Ring

   Courtesy of BMW OF NORTH AMERICA, INC.

Installation location of RDC wheel electronic unit 

1. Wheel electronic unit
2. Support ring
   Fig 6: Identifying Wheel Electronic And Unit Support Ring

   Courtesy of BMW OF NORTH AMERICA, INC.

For further information on the subject of "Tire pressure warning systems and tires with emergency running characteristics"  , please refer to the vehicle Owner's Handbook.