If you did something like this you might want to study up on your vehicle a little more. You know you can't put grease in place of motor oil right - just razzing you! If you are forced to drive the VX with these mismatched tires you might want to add some air pressure to the smaller tires and take some air out of the larger tires to try to bring the opposing sizes to closer diameters. Be extra careful driving it around like that.