Division 4.2.8.5 Calculation of the wet grip index of the candidate tyreF1

United Kingdom

The wet grip index of the candidate tyre ( G(T) ) is calculated as follows:

$G(T) = [\frac{μ_{peak,ave} (T)}{μ_{peak,ave} (R)} \times 125 + a \times (t - t_{0}) + b \times (\frac{μ_{peak,ave} (R)}{μ_{peak,ave} {(R}_{0})} - 1,0)] \times 10^{- 2}$

where:

t is the measured wet surface temperature in degree Celsius when the candidate tyre ( T ) is tested
t ₀ is the wet surface reference temperature condition
t ₀ = 20 °C for normal tyres t ₀ = 10 °C for snow tyres
μ _peak,ave (R ₀ ) = 0,85 is the peak braking force coefficient for the reference tyre in the reference conditions
a = – 0,4232 and b = - 8,297 for normal tyres, a = 0,7721 and b = 31,18 for snow tyres.

Annotations

Textual amendments

F1: Inserted by Commission Regulation (EU) No 228/2011 of 7 March 2011 amending Regulation (EC) No 1222/2009 of the European Parliament and of the Council with regard to the wet grip testing method for C1 tyres (Text with EEA relevance).