Technical Focus: Road Surface

By Michelin Sport
May 18 2005

The nature of the road surface at Monaco is among its most striking features. Used by regular traffic throughout the year, its characteristics are very distinctive.

When considering grip at any venue, you have to weigh up the state of two elements: tyres and the road surface. The latter's characteristics (the type of asphalt and its roughness) and the prevailing conditions (surface cleanliness, rain etc) will influence grip significantly.

To define the grip characteristics of a street circuit, its surface geometry has to be examined and assessed in several ways:

* Macroroughness - It contributes to the drainage and storage of water, as well as tyre indentation . Macroroughness occurs due to the size of the aggregates used in the composition of the road surface.

* Microroughness - It is mainly responsible for tyre indentation. Microroughness is related to the surface imperfections of the aggregates and sands used in the road surface's composition.

* Surface - The load-bearing surface must also be considered because it determines localised pressures within the tyre's contact patch (as detailed in the Spanish GP preview).

Measurement of macroroughness:

Macroroughness can be measured on a road surface, a core sample or a moulding made of the surface.

Measurement of microroughness:

Microroughness is assessed by indirect methods. In particular, the level of microroughness is evaluated by taking aggregate surface photos. These photos are then compared with a subjective scale, graduated from 1 (for an extra-smooth surface) to 100 (for a particularly rough surface).



The friction - or grip - co-efficient can only be defined in terms of the relationship between a tyre and the road surface.

In an urban setting, road surfaces can be classified in four main categories:



In this context, Monaco is classified as macrosmooth. The contact ratio is quite high, which makes it kinder on tyres.