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235/35R20 vs 275/35R20

275/35R20 is outside the ±3% rule as a replacement for 235/35R20: the diameter differs by +4.16%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.

20" rim
235/35R20 26.48" · 275/35R20 27.58" · drawn to scale

Side by side

235/35R20275/35R20Difference
Overall diameter26.48"27.58"+1.10" (+4.16%)
Section width235 mm275 mm+40 mm
Sidewall3.24"3.79"+0.55"
Rim20"20"same
Circumference83.2"86.6"+3.5"
Revs per mile762731-30
Ride height——+0.55"
Speedometer reads 60 mph60.062.5+2.5 mph

Speedometer and odometer

020406080100120 reads 60 · actual 62.5 mph

With 275/35R20 on a car calibrated for 235/35R20, the speedometer reads 57.6 mph when you're really doing 60, and the odometer under-counts by 4.2%.

Speedo showsActual speed
30 mph31.2 mph
45 mph46.9 mph
60 mph62.5 mph
70 mph72.9 mph
80 mph83.3 mph

Other sizes close to 235/35R20

Questions

Can I replace 235/35R20 with 275/35R20?

275/35R20 is outside the ±3% rule as a replacement for 235/35R20: the diameter differs by +4.16%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.

What's the difference between 235/35R20 and 275/35R20?

275/35R20 is 1.10" taller and 40 mm wider; the sidewall is +0.55". At an indicated 60 mph you'd actually be doing 62.5 mph.

Will 275/35R20 fit on 235/35R20 wheels?

Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 275 mm tire and the fender clearance.