Tire Size Box

235/70R13 vs 235/80R13

235/80R13 compared with 235/70R13

+7.1% diameter, 0.0" width

235/80R13 is 27.80" tall vs 25.95". More than the 3% rule of thumb, so check carefully before switching.

26.0"13" rim6.5"9.3" wide
235/70R13 (solid) compared with 235/80R13 (dashed outline), drawn to scale

With 235/80R13 tires, when your speedometer says 60 mph you are really going

64.3 mph

235/80R13 is +1.85 inches (+7.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

235/70R13235/80R13Difference%
Overall diameter25.95"27.80"+1.85"+7.1%
Section width9.25"9.25"0.00"0.0%
Sidewall height6.48"7.40"+0.93"+14.3%
Circumference81.53"87.35"+5.81"+7.1%
Revolutions per mile777.1725.4−51.7−6.7%

Speedometer difference

If your vehicle came with 235/70R13 and you fit 235/80R13, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.4 mph+1.4 mph
30 mph32.1 mph+2.1 mph
40 mph42.9 mph+2.9 mph
50 mph53.6 mph+3.6 mph
60 mph64.3 mph+4.3 mph
65 mph69.6 mph+4.6 mph
70 mph75.0 mph+5.0 mph
75 mph80.3 mph+5.3 mph
80 mph85.7 mph+5.7 mph

Each size on its own

Questions

Which is bigger, 235/70R13 or 235/80R13?
235/80R13 is taller by 1.85 inches (27.80" vs 25.95"). 235/70R13 is the same width.
Can I replace 235/70R13 with 235/80R13?
It is not recommended without checking carefully. The diameter difference is +7.1%, more than the 3% most shops and makers allow. It will throw off the speedometer and may affect ABS, stability control and clearance.
How much will 235/80R13 change my speedometer?
When your speedometer reads 60 mph with 235/80R13 fitted (calibrated for 235/70R13), your real speed is 64.3 mph. Your odometer will under-count miles by about 7.1%.
Will 235/80R13 lift my vehicle?
Ride height changes by half the diameter difference: +0.93 inches of ground clearance at the axle.

Other comparisons