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37x12.50R20 vs 37x13.50R20

37x13.50R20 is a safe swap for 37x12.50R20 by the usual ±3% rule: the diameter differs by 0.00%.

20" rim
37x12.50R20 37.00" · 37x13.50R20 37.00" · drawn to scale

Side by side

37x12.50R2037x13.50R20Difference
Overall diameter37.00"37.00"0.00" (0.00%)
Section width318 mm343 mm+25 mm
Sidewall8.50"8.50"0.00"
Rim20"20"same
Circumference116.2"116.2"0.0"
Revs per mile5455450
Ride height——0.00"
Speedometer reads 60 mph60.060.00.0 mph

Speedometer and odometer

020406080100120 reads 60 · actual 60.0 mph

With 37x13.50R20 on a car calibrated for 37x12.50R20, 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 37x12.50R20

Questions

Can I replace 37x12.50R20 with 37x13.50R20?

37x13.50R20 is a safe swap for 37x12.50R20 by the usual ±3% rule: the diameter differs by 0.00%.

What's the difference between 37x12.50R20 and 37x13.50R20?

37x13.50R20 is 0.00" taller and 25 mm wider; the sidewall is 0.00". At an indicated 60 mph you'd actually be doing 60.0 mph.

Will 37x13.50R20 fit on 37x12.50R20 wheels?

Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 343 mm tire and the fender clearance.