235/50R18
235/50R18 ships as an OEM size on the Cadillac CT5. At 27.25″ diameter with a 4.63″ sidewall (50% of section width), this size turns 740 revolutions per mile.
About 235/50R18
Factory fitments for 235/50R18 include the Cadillac CT5 — meaning replacement tires in this size see steady demand and broad brand availability. At 27.25″ overall diameter, 235/50R18 turns 740 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 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 225/50R18 drops diameter by 1.44%, which stays within the ±3% fitment safe zone for most vehicles. Stepping up to 215/55R18 adds 0.22% 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 27.25″ 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 aliases235/50R18
- Diameter
- 27.25″ / 692.2mm
- Section Width
- 9.25″
- Sidewall
- 4.63″ / 117.5mm
- Circumference
- 85.61″
- Revs/Mile
- 740
215/50R18
- Diameter
- 26.46″ / 672.2mm
- Section Width
- 8.46″
- Sidewall
- 4.23″ / 107.5mm
- Circumference
- 83.14″
- Revs/Mile
- 762
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 58.27 mph (93.77 km/h). Your speedometer reads 2.89% high versus actual speed.