245/45R20
245/45R20 ships as an OEM size on the Buick Envision, Chrysler 300, Dodge Challenger. At 28.68″ diameter with a 4.34″ sidewall (45% of section width), this size turns 703 revolutions per mile.
About 245/45R20
Factory fitments for 245/45R20 include the Buick Envision, Chrysler 300, Dodge Challenger — meaning replacement tires in this size see steady demand and broad brand availability. At 28.68″ overall diameter, 245/45R20 turns 703 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 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 235/45R20 drops diameter by 1.24%, which stays within the ±3% fitment safe zone for most vehicles. Stepping up to 255/45R20 adds 1.24% 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 28.68″ 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 aliases245/45R20
- Diameter
- 28.68″ / 728.5mm
- Section Width
- 9.65″
- Sidewall
- 4.34″ / 110.25mm
- Circumference
- 90.1″
- Revs/Mile
- 703
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 57.32 mph (92.25 km/h). Your speedometer reads 4.46% high versus actual speed.