For the tie-rod end ball joints of small size buses with front axle suspensions, the sealing structure of the dust boots is not appropriate, and therefore, muddy water etc. can seep into the ball joints and cause the resin bearings to wear, in which case the bearings may start to rattle. If this problem is left unattended, the rattle may increase, and in the worst case, the ball joint could come off the tie-rod, which could cause the vehicle to stall.