215/55R18

About 215/55R18

Factory fitments for 215/55R18 include the Kia Niro, Kia Seltos, Mazda CX-30 — meaning replacement tires in this size see steady demand and broad brand availability. At 27.31″ overall diameter, 215/55R18 turns 738 revolutions per mile, which is the reference point the factory speedometer and odometer were calibrated against. The 55% 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 235/50R18 drops diameter by 0.22%, which stays within the ±3% fitment safe zone for most vehicles. Stepping up to 225/55R18 adds 1.59% 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 27.31″ stock diameter (about ±2% in percentage terms) will keep ABS, TPMS, and odometer readings inside the vehicle's designed tolerance.

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