What is ISO 4209‑2 about?
ISO 4209‑2 is an international standard and part two of a multi-series of documents on truck and bus tyres and rims.
ISO 4209‑2 specifies the designations, contours and dimensions of drop-centre (one-piece) rims for use on trucks and buses. The rim dimensions are those rim contour dimensions necessary for mounting and fitment of the tyre to the rim.
Note: Tyre designations, dimensions and load ratings are given in ISO 4209‑1.
Who is ISO 4209‑2 for?
ISO 4209‑2 on truck and bus tyres and rims is useful for: 
- Truck and bus manufacturers
- Tyre and rims manufacturers
Why should you use ISO 4209‑2?
The drop center rim is the typical rim shape for car rims. Every rim is actually a drop center rim. Tubeless tires are fitted to the car, making deep bed rims the only rim shape possible. The reason for using this rim shape is that the tubeless tire can be used safely and with a large volume of air.
ISO 4209‑2 on truck and bus tyres and rims focuses on the designations, contours and dimensions of drop-centre rims. These rims may have an elevated portion of the rim bead seat, a safety contour called hump. Hump enables better tire fitting on the rim, prevents bead from slipping down when the vehicle is moving at a high speed and stops air escaping when cornering at reduced tire pressure. This will reduce the risk of accidents and increase safety for trucks and buses.
What’s changed since the last update?
BS ISO 4209‑2:2020 supersedes BS ISO 42092:2012, which is withdrawn.
BS ISO 4209‑2:2020 has figures and notes has been corrected with respect to BS ISO 42092:2012.
