240SX Wheel & Tire Fitment Planning Guide
How tire diameter, wheel width, offset, suspension, alignment and body clearance interact on S13 and S14 cars.
Offset is only one dimension
Two wheels with the same offset can have very different inner and outer positions if their widths differ. Compare bead-seat width and offset together, then physically account for tire section width, rim-protector shape, coilover spring/perch location, brake caliper clearance and fender shape.
Tire labels are nominal
A 245/40R17 from one tire line may measure differently from another on the same rim. Use the tire manufacturer’s measured section width and approved rim-width range for a final fitment decision. The calculator on this site is geometry, not a clearance guarantee.
Alignment changes clearance
Negative camber can improve upper-fender clearance while decreasing other clearances depending on suspension motion. Caster and steering angle change where the tire sweeps during lock. Drift steering kits and altered control arms can move the wheel substantially from factory geometry.
Check dynamically
Test full steering lock, suspension compression and droop as relevant. A car that clears while parked can rub the harness, frame, sway bar, tension rod, fender liner or quarter lip in motion. Protect critical wiring from tire contact.
Chassis condition, donor version, aftermarket geometry and local legal requirements vary. Measure your car and use the correct factory/component documentation before fabrication or safety-critical work.