The 1998 Mazda B4000 tire size depends on trim: the 2D Pickup Extra Cab, 4WD, Standard takes P265/75R15 112S; the 2D Pickup Extra Cab, 4WD, Automatic takes P265/75R15 112S; the 2D Pickup Extra Cab, RWD, Automatic takes P225/70R14 98S; the 2D Pickup Extra Cab, RWD, Standard takes P225/70R14 98S; the 4D Pickup Extra Cab, 4WD, Automatic takes P265/75R15 112S; the 4D Pickup Extra Cab, 4WD, Standard takes P265/75R15 112S; the 4D Pickup Extra Cab, RWD, Automatic takes P225/70R14 98S; the 4D Pickup Extra Cab, RWD, Standard takes P225/70R14 98S, per the factory service manual.
Factory-Spec Tire Size
Varies by trim
2D Pickup Extra Cab, 4WD, Standard: P265/75R15 112S
2D Pickup Extra Cab, 4WD, Automatic: P265/75R15 112S
2D Pickup Extra Cab, RWD, Automatic: P225/70R14 98S
2D Pickup Extra Cab, RWD, Standard: P225/70R14 98S
4D Pickup Extra Cab, 4WD, Automatic: P265/75R15 112S
4D Pickup Extra Cab, 4WD, Standard: P265/75R15 112S
4D Pickup Extra Cab, RWD, Automatic: P225/70R14 98S
4D Pickup Extra Cab, RWD, Standard: P225/70R14 98S