CarSpecsHQ

33x12.50R17 vs 33x12.50R18

33x12.50R18 is a safe swap for 33x12.50R17 by the usual ±3% rule: the diameter differs by 0.00%.

17" → 18"
33x12.50R17 33.00" · 33x12.50R18 33.00" · drawn to scale

Side by side

33x12.50R1733x12.50R18Difference
Overall diameter33.00"33.00"0.00" (0.00%)
Section width318 mm318 mm0 mm
Sidewall8.00"7.50"-0.50"
Rim17"18"+1"
Circumference103.7"103.7"0.0"
Revs per mile6116110
Ride height——0.00"
Speedometer reads 60 mph60.060.00.0 mph

Speedometer and odometer

020406080100120 reads 60 · actual 60.0 mph

With 33x12.50R18 on a car calibrated for 33x12.50R17, the speedometer reads 60.0 mph when you're really doing 60, and the odometer over-counts by 0.0%.

Speedo showsActual speed
30 mph30.0 mph
45 mph45.0 mph
60 mph60.0 mph
70 mph70.0 mph
80 mph80.0 mph

Other sizes close to 33x12.50R17

Questions

Can I replace 33x12.50R17 with 33x12.50R18?

33x12.50R18 is a safe swap for 33x12.50R17 by the usual ±3% rule: the diameter differs by 0.00%.

What's the difference between 33x12.50R17 and 33x12.50R18?

33x12.50R18 is 0.00" taller and 0 mm wider; the sidewall is -0.50". At an indicated 60 mph you'd actually be doing 60.0 mph.

Will 33x12.50R18 fit on 33x12.50R17 wheels?

No — 33x12.50R17 needs a 17" wheel and 33x12.50R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.