Road surface condition estimating method, vehicle control method, and road surface condition estimating apparatus

An apparatus for estimating a road surface condition, comprising:

• a tire for estimation of a road surface condition, the tire having at least one row of blocks and lug grooves, each lug groove being disposed between adjacent blocks of the row of blocks, the total number N of the circumferentially disposed blocks and corresponding lugs grooves being 10 or more, a number n of the lug grooves, are provided with a joining section connecting circumferentially adjacent blocks, a relation between n and the total number N satisfying the range of (N/2)≦n≦(N−5);
• a vibrations detecting unit disposed in an unsprung portion of a vehicle for detecting vibrations of a tire tread propagated to the unsprung portion from the tire;
• a rotational order components extracting unit for performing a rotational order ratio analysis on the vibrations of the tire tread detected by the vibrations detecting unit and extracting the amplitude of a rotational order component whose order is (N−n);
• and
• a road surface condition estimating unit for estimating a current road surface condition from the extracted amplitude of the rotational order component.