265/40R21
265/40R21 ships as an OEM size on the Ford Edge. At 29.35″ diameter with a 4.17″ sidewall (40% of section width), this size turns 687 revolutions per mile.
About 265/40R21
Factory fitments for 265/40R21 include the Ford Edge — meaning replacement tires in this size see steady demand and broad brand availability. At 29.35″ overall diameter, 265/40R21 turns 687 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 21″ rim pairing is typical for luxury SUV and performance-oriented platforms, so compatible wheels are easy to source new or used. Going one step shorter to 285/35R21 drops diameter by 1.68%, which stays within the ±3% fitment safe zone for most vehicles. Stepping up to 275/40R21 adds 1.07% 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 29.35″ 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 aliases265/40R21
- Diameter
- 29.35″ / 745.4mm
- Section Width
- 10.43″
- Sidewall
- 4.17″ / 106mm
- Circumference
- 92.19″
- Revs/Mile
- 687
255/35R21
- Diameter
- 28.03″ / 711.9mm
- Section Width
- 10.04″
- Sidewall
- 3.51″ / 89.25mm
- Circumference
- 88.05″
- Revs/Mile
- 720
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 57.3 mph (92.22 km/h). Your speedometer reads 4.49% high versus actual speed.