The Nitto NT555 G2 in size 225/40ZR18 is a summer ultra-high-performance radial tire with service description 92W. The NT555 G2 is Nitto’s summer performance tire for passenger-car applications.
Size and wheel specifications
- Tire size: 225/40ZR18
- Manufacturer stock number: 211180
- Wheel diameter: 18 in
- Nominal section width: 225 mm
- Load index / speed rating: 92W
- Load designation: XL (Extra Load)
- Approved rim-width range: 7.5–9.0 in
- Measuring rim width: 8.0 in
- Manufacturer-listed overall diameter: 25.08 in
- Manufacturer-listed overall width: 9.06 in
- Tread depth: 11.0/32 in
- Maximum load / inflation rating: 1,389 lb at 50 psi
Nitto lists this exact stock number at 25.08 inches overall diameter and 9.06 inches overall width on the 8.0-inch measuring rim. The measuring rim is the reference for those published dimensions; the approved rim-width range is 7.5–9.0 inches.
Before ordering
Compare the complete size, load index and speed rating with your vehicle’s approved requirements. Confirm wheel width, wheel load capacity and clearance as well as diameter. A tire’s dimensions do not establish an OEM vehicle application. If changing tire size or type, have the combination and operating pressure checked by a qualified tire professional.
Questions about 225/40ZR18
What do the numbers in 225/40ZR18 mean?
The size uses a nominal 225 mm section width and an aspect ratio of 40; the sidewall height is expressed as a percentage of that nominal width. R denotes radial construction and 18 is the wheel diameter in inches. Nitto lists this exact tire at 25.08 inches overall diameter and 9.06 inches overall width on the 8.0-inch measuring rim.
What wheel width is approved for this 225/40ZR18 tire?
Nitto lists 7.5–9.0 inches as the approved rim-width range for stock number 211180. Its 8.0-inch measuring rim is the reference for the published dimensions, not the only approved width. The wheel must also have the correct 18-inch diameter and be suitable for the vehicle and required load.
What does the 92W XL marking tell me?
92 is the tire’s load index and W is its speed symbol. XL means Extra Load; it is a load designation, not a statement of the number of physical casing plies. Use the complete size and service description when checking a replacement against the vehicle’s approved requirements; the tire model name alone is not enough.
Is 50 psi the pressure I should run in this tire?
No. The listed 1,389 lb at 50 psi is Nitto’s maximum load/inflation rating. It is not a recommended pressure for every vehicle. Follow the applicable vehicle and tire guidance, and have the operating pressure confirmed when changing tire size, type or load requirements.
Will this 225/40ZR18 tire fit any vehicle with 18-inch wheels?
No. A matching 18-inch wheel diameter is only one requirement. Check the approved 7.5–9.0-inch rim-width range, complete 92W service description, wheel load capacity and vehicle clearance. The published 25.08-inch diameter is useful for comparison, but does not prove vehicle fitment or that a lift or modification is unnecessary.
