Each pneumatic tire disposed on the rear wheel side has a total groove surface area ratio of 20% or more and 27% or less in ground-contacting width. Each pneumatic tire disposed on the front wheel side and the rear wheel side has a smaller groove surface area ratio on the vehicle outer side than on the vehicle inner side in the ground-contacting width. The difference in the groove surface area ratio is 7% or more and 15% or less. The total groove surface area ratio is greater on the front wheel side than on the rear wheel side, the difference in the total groove surface area ratio being 3% or more and 10% or less.