@def FZ_RL begin #(N, F_yf, F_yr, V, Ax, R)

	# define the lateral tire forces
	F_yf=@F_YF()
	F_yr=@F_YR()
	FZ_rl = zeros(Float64, (length(Ax),1))
	for ii in eachindex(Ax)
		FZ_rl[ii] = 0.5*(FzR0 + KZX*(Ax[ii] - V[ii]*R[ii])) - KZYR*((F_yf[ii] + F_yr[ii])/m)
	end
	FZ_rl
end
