Imagine never having to check your tire pressure again. This innovation called SIT (for self-inflating tire), from Coda Development, a Czech company uses the energy of the wheel to self-inflate the tire as needed, keeping the tire always at its optimum pressure level.

It works on the principle of Peristalsis – the radially symmetrical contraction and relaxation of a portion of a tube that propagates a wave, in an anterograde direction, much the same way a human digestive gastrointestinal tract functions where a smooth muscle tissue contracts in sequence to produce a peristaltic wave, which propels a ball of food along the tract.

The SIT system integrates a peristaltic tube chamber into the tire wall. The chamber is kept closed at its lowest point by normal tire deformation caused by the vehicle’s weight.  As the tire rolls against the road, the closure moves along the peristaltic tube chamber forcing more air into the tire with each wheel revolution.

When a vehicle equipped with SIT tires is put in motion, under-inflated tires will automatically re-inflate to their optimal operation pressure, which the system constantly maintains while the tires are in use.

The clever SIT design is extremely simple, consisting only of two new tire components – the peristaltic tube chamber and an automatic pressure regulator with an interface connecting the tire interior with the outside environment.

Inflation is activated only when the tire pressure falls below its optimal level.

When the optimal tire pressure is reached, the automatic pressure regulator disables the intake of atmospheric air and activates continuous internal air circulation between the tire and the peristaltic chamber. This is important as it takes the load of the system while it is not required to pump the tire, i.e. when the tire is properly inflated, which is almost 100% of the time.

As a result, SIT tires will always operate at optimal pressure. Driving for 1 km will compensate for typical monthly leakage of 2-3%.

Proper tire inflation reduces fuel consumption and emissions, extends tire life, and, most importantly, improves vehicle safety. 

SIT is also designed to fit existing tires.

Goodyear Tire & Rubber Company has been working on a similar design called Air Maintenance Technology (AMT), which has been challenged in court by Coda Development. On 22 February 2019, the District of Columbia US Federal Court of Appeal reversed a trial court’s decision to dismiss Coda’s claims against Goodyear Tire & Rubber Company for misappropriation of trade secrets and failure to identify the true inventors on Goodyear patents.  The appellate court has remanded the case to the trial court for consideration on the merits.

Coda says that it welcomes the Court’s decision and looks forward to an eventual decision on the merits of its claims.  Coda also will continue its efforts to bring this game-changing technology to the market.

SIT website:

Leave a Reply

Your email address will not be published. Required fields are marked *


Access further archives on our Archive Documents page.



A community of Citroën enthusiasts with a passion for Citroën automobiles.

Citroënvie © Copyright 2023. All rights reserved.