CarSpecsHQ

205/50R17 vs 265/35R18

265/35R18 is a safe swap for 205/50R17 by the usual ±3% rule: the diameter differs by +0.93%.

17" → 18"
205/50R17 25.07" · 265/35R18 25.30" · drawn to scale

Side by side

205/50R17265/35R18Difference
Overall diameter25.07"25.30"+0.23" (+0.93%)
Section width205 mm265 mm+60 mm
Sidewall4.04"3.65"-0.38"
Rim17"18"+1"
Circumference78.8"79.5"+0.7"
Revs per mile804797-7
Ride height——+0.12"
Speedometer reads 60 mph60.060.6+0.6 mph

Speedometer and odometer

020406080100120 reads 60 · actual 60.6 mph

With 265/35R18 on a car calibrated for 205/50R17, the speedometer reads 59.4 mph when you're really doing 60, and the odometer under-counts by 0.9%.

Speedo showsActual speed
30 mph30.3 mph
45 mph45.4 mph
60 mph60.6 mph
70 mph70.6 mph
80 mph80.7 mph

Other sizes close to 205/50R17

Questions

Can I replace 205/50R17 with 265/35R18?

265/35R18 is a safe swap for 205/50R17 by the usual ±3% rule: the diameter differs by +0.93%.

What's the difference between 205/50R17 and 265/35R18?

265/35R18 is 0.23" taller and 60 mm wider; the sidewall is -0.38". At an indicated 60 mph you'd actually be doing 60.6 mph.

Will 265/35R18 fit on 205/50R17 wheels?

No — 205/50R17 needs a 17" wheel and 265/35R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.