235/50R21
235/50R21 ships as an OEM size on the Lexus RX. At 30.25″ diameter with a 4.63″ sidewall (50% of section width), this size turns 667 revolutions per mile.
About 235/50R21
Factory fitments for 235/50R21 include the Lexus RX — meaning replacement tires in this size see steady demand and broad brand availability. At 30.25″ overall diameter, 235/50R21 turns 667 revolutions per mile, which is the reference point the factory speedometer and odometer were calibrated against. The 50% aspect ratio gives it a moderate sidewall suited to sporty street driving and responsive turn-in. 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 255/45R21 drops diameter by 0.72%, which stays within the ±3% fitment safe zone for most vehicles. If you are shopping for a direct replacement, any tire within roughly ±0.7″ of the 30.25″ 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 aliases235/50R21
- Diameter
- 30.25″ / 768.4mm
- Section Width
- 9.25″
- Sidewall
- 4.63″ / 117.5mm
- Circumference
- 95.04″
- Revs/Mile
- 667
255/45R21
- Diameter
- 30.04″ / 762.9mm
- Section Width
- 10.04″
- Sidewall
- 4.52″ / 114.75mm
- Circumference
- 94.36″
- Revs/Mile
- 671
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 59.57 mph (95.87 km/h). Your speedometer reads 0.72% high versus actual speed.