Read the letter in its position
In 205/55 R16, R sits between aspect ratio and wheel diameter. Here it describes construction. Radial tyres use the corresponding arrangement of carcass cords. This is a structural designation, not by itself a statement about summer or winter suitability, comfort or test ranking.
The same letter elsewhere may mean something different. A speed symbol, for example, appears in the service description after the load index. Read the entire sequence rather than an isolated R somewhere on the sidewall. Product names may also contain the letter.
Construction alone is not an order specification
Radial construction is common on modern passenger cars. The word is still insufficient for ordering. Size, capacity, speed requirements and additional instructions remain necessary. A replacement must match the intended vehicle equipment. Unclear construction requirements on older vehicles or special applications should be resolved with a knowledgeable source.
Different constructions cannot be mixed arbitrarily. Relevant requirements under Section 36 StVZO apply to ordinary passenger cars in Germany. A period appearance or one tyre already in storage is not sufficient justification for departing from the intended specification.
What a cutaway can explain
A schematic cutaway can show the carcass, belts and bead. It does not approve a particular product for a vehicle. Different radial tyres can vary in many further characteristics. Use a section drawing to understand terminology, not to rank quality by counting illustrated lines.
Copy the full marking when ordering and verify it against the documents. If a shop omits construction or uses an unusual description, ask before fitting. Clear identification matters particularly when adding to an older existing wheel set. R is one component of that identification, not a replacement for the other details. Keep any specialist advice with the vehicle record so that a later supplier does not repeat the same uncertainty from the beginning.
With designations containing additional letters such as ZR, the full service description must still be considered. Do not infer an allowable speed from R alone. Vehicle requirements and the tyre manufacturer's information establish the actual application, rather than an isolated letter.
