275/45R18
275/45R18 is uncommon as OEM fitment but appears as an aftermarket upsize option. At 27.74″ diameter with a 4.87″ sidewall (45% of section width), this size turns 727 revolutions per mile.
About 275/45R18
275/45R18 is less common as a factory fitment but is available as an aftermarket size, so SKU selection is narrower than mainstream OEM sizes. At 27.74″ overall diameter, 275/45R18 turns 727 revolutions per mile, which is the reference point the factory speedometer and odometer were calibrated against. The 45% 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. Going one step shorter to 265/45R18 drops diameter by 1.28%, which stays within the ±3% fitment safe zone for most vehicles. Stepping up to 255/50R18 adds 1.06% 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 27.74″ 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 aliases275/45R18
- Diameter
- 27.74″ / 704.7mm
- Section Width
- 10.83″
- Sidewall
- 4.87″ / 123.75mm
- Circumference
- 87.16″
- Revs/Mile
- 727
255/45R18
- Diameter
- 27.04″ / 686.7mm
- Section Width
- 10.04″
- Sidewall
- 4.52″ / 114.75mm
- Circumference
- 84.93″
- Revs/Mile
- 746
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 58.47 mph (94.09 km/h). Your speedometer reads 2.55% high versus actual speed.