215/40R18
215/40R18 ships as an OEM size on the Subaru BRZ. At 24.77″ diameter with a 3.39″ sidewall (40% of section width), this size turns 814 revolutions per mile.
About 215/40R18
Factory fitments for 215/40R18 include the Subaru BRZ — meaning replacement tires in this size see steady demand and broad brand availability. At 24.77″ overall diameter, 215/40R18 turns 814 revolutions per mile, which is the reference point the factory speedometer and odometer were calibrated against. The 40% aspect ratio gives it a low-profile sidewall that delivers sharp steering response but transmits road imperfections. The 18″ rim pairing is typical for full-size truck, premium SUV, and sport-sedan platforms, so compatible wheels are easy to source new or used. Stepping up to 225/40R18 adds 1.27% diameter — also inside the safe window, with marginally taller ride height. If you are shopping for a direct replacement, any tire within roughly ±0.7″ of the 24.77″ stock diameter (about ±2% in percentage terms) will keep ABS, TPMS, and odometer readings inside the vehicle's designed tolerance.
Compare with another size
275/65R18 or "33" for inch aliases215/40R18
- Diameter
- 24.77″ / 629.2mm
- Section Width
- 8.46″
- Sidewall
- 3.39″ / 86mm
- Circumference
- 77.82″
- Revs/Mile
- 814
215/45R18
- Diameter
- 25.62″ / 650.7mm
- Section Width
- 8.46″
- Sidewall
- 3.81″ / 96.75mm
- Circumference
- 80.48″
- Revs/Mile
- 787
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 62.05 mph (99.86 km/h). Your speedometer reads 3.42% low versus actual speed.