The Future of Self-inflating Tires

Michelin is working with several other companies to develop an active pressure-management system called TIPM (Tire Intelligent Pressure Management), due to be available sometime in 2005. This system has a compressor that automatically adjusts the pressure in each tire while the vehicle is in operation to compensate for leaks and slow-leak punctures. The driver will be able to adjust the pressure depending on the desired driving mode: comfort, sporty, all-terrain or over-obstacle.

There are at least two other systems in the early development stages that are oriented toward the consumer market -- the EnTire system and the Cycloid AirPump system.

The EnTire Self-Inflating Tire ­system uses a valve that pulls in air from the atmosphere. It then pumps the air into the under-inflated tire using a peristaltic-pump action. The goal is to constantly maintain a specific pressure.

EnTire self-inflating tire system peristaltic pump mechanism
The EnTire system is based on this type of peristaltic pump mechanism.

The AutoPump tire-inflator system by Cycloid has a small, wheel-hub-mounted pump that is powered by the turning of the wheels. When the system's monitor detects a drop in pressure of 2 to 3 psi, it pumps air into the underinflated tire. AutoPump has a warning system that is activated when there is a puncture. 

Self-inflating Tires for Bicycles and Motorcycles
 Now cyclists can also motor with the peace of mind that a flat tire isn't going to ruin their ride. Bridgestone Cycle of Japan has developed the Air Hub, which uses a rotating air pump that replenishes air in the tire as you pedal. Like the EnTire method, it keeps the air in the tires at a constant pressure level. The air pump is in the hub and is run by the rotation of the wheel. A small tube runs compressed air to the tire's air valve to maintain the pressure. When the air pressure in the tire is where it should be, excess air is exhausted through a device in the middle of the hose.

Pirelli has also come up with a self-inflating tire system for motorcycles and scooters. The Pirelli Safety Wheel System uses a monitoring system along with a special rim and an internal tube containing compressed air. It also has a valve to regulate the pressure between the tube and the tire. When the tire deflates naturally, the valve opens and pumps air into the tire until it reaches the correct pressure. If there is a puncture, the system warns the rider as it allows air to move into the tire.

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