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275/35R20 vs 315/35R20

315/35R20 is outside the ±3% rule as a replacement for 275/35R20: the diameter differs by +4.00%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.

20" rim
275/35R20 27.58" · 315/35R20 28.68" · drawn to scale

Side by side

275/35R20315/35R20Difference
Overall diameter27.58"28.68"+1.10" (+4.00%)
Section width275 mm315 mm+40 mm
Sidewall3.79"4.34"+0.55"
Rim20"20"same
Circumference86.6"90.1"+3.5"
Revs per mile731703-28
Ride height——+0.55"
Speedometer reads 60 mph60.062.4+2.4 mph

Speedometer and odometer

020406080100120 reads 60 · actual 62.4 mph

With 315/35R20 on a car calibrated for 275/35R20, the speedometer reads 57.7 mph when you're really doing 60, and the odometer under-counts by 4.0%.

Speedo showsActual speed
30 mph31.2 mph
45 mph46.8 mph
60 mph62.4 mph
70 mph72.8 mph
80 mph83.2 mph

Other sizes close to 275/35R20

Questions

Can I replace 275/35R20 with 315/35R20?

315/35R20 is outside the ±3% rule as a replacement for 275/35R20: the diameter differs by +4.00%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.

What's the difference between 275/35R20 and 315/35R20?

315/35R20 is 1.10" taller and 40 mm wider; the sidewall is +0.55". At an indicated 60 mph you'd actually be doing 62.4 mph.

Will 315/35R20 fit on 275/35R20 wheels?

Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 315 mm tire and the fender clearance.