255/40R20
255/40R20 ships as an OEM size on the Acura TLX, Audi A6, Volkswagen Tiguan. At 28.03″ diameter with a 4.02″ sidewall (40% of section width), this size turns 719 revolutions per mile.
About 255/40R20
Factory fitments for 255/40R20 include the Acura TLX, Audi A6, Volkswagen Tiguan — meaning replacement tires in this size see steady demand and broad brand availability. At 28.03″ overall diameter, 255/40R20 turns 719 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 20″ 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 245/40R20 drops diameter by 1.12%, which stays within the ±3% fitment safe zone for most vehicles. Stepping up to 235/45R20 adds 1.05% 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 28.03″ 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 aliases255/40R20
- Diameter
- 28.03″ / 712mm
- Section Width
- 10.04″
- Sidewall
- 4.02″ / 102mm
- Circumference
- 88.06″
- Revs/Mile
- 719
235/40R20
- Diameter
- 27.4″ / 696mm
- Section Width
- 9.25″
- Sidewall
- 3.7″ / 94mm
- Circumference
- 86.08″
- Revs/Mile
- 736
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 58.65 mph (94.39 km/h). Your speedometer reads 2.25% high versus actual speed.