A lot of classic cars, such as the Fiat 500, are equipped with so-called White Wall tyres. The problem with these tyres is that the White Wall turns a bit brown over time.
We use Soft Soap (Driehoek Groene Zeep) to remove the brownish layer. Wet the tyre (White Wall) with water. Then rub some green soap on the White Wall with a cloth. Let this soak in for a while. After a few minutes, rub it off with sufficient water and rinse the White Wall with water.

After doing this, you get the following result. At least, we got this result:


In the video below, jet can see the result again:
In this case, we used Radar Dimax Classic tyres. We do not know if the same results can be obtained with other types of tyres. If you are looking for tyres with White Walls, check out this category: Tires