Hydroplaning speed (kts) = 9 √ (P / ρ)
Where P is tyre pressure in psi
and ρ is specific gravity of contaminants.
If pressure is given in bars x by 14.5
specific gravity of water = 1
So...
tyre pressure = 10.8 x 14.5 = 156.6 psi
so 9 x √156.6 / 1
= 9 x 12.51
= 112 kts