Tire Size Box

285/25R21 vs 285/35R21

285/35R21 compared with 285/25R21

+8.4% diameter, 0.0" width

285/35R21 is 28.85" tall vs 26.61". More than the 3% rule of thumb, so check carefully before switching.

26.6"21" rim2.8"11.2" wide
285/25R21 (solid) compared with 285/35R21 (dashed outline), drawn to scale

With 285/35R21 tires, when your speedometer says 60 mph you are really going

65.1 mph

285/35R21 is +2.24 inches (+8.4%) in overall diameter. That is more than the 3% most shops and makers recommend.

285/25R21285/35R21Difference%
Overall diameter26.61"28.85"+2.24"+8.4%
Section width11.22"11.22"0.00"0.0%
Sidewall height2.81"3.93"+1.12"+40.0%
Circumference83.60"90.65"+7.05"+8.4%
Revolutions per mile757.9699.0−58.9−7.8%

Speedometer difference

If your vehicle came with 285/25R21 and you fit 285/35R21, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.7 mph+1.7 mph
30 mph32.5 mph+2.5 mph
40 mph43.4 mph+3.4 mph
50 mph54.2 mph+4.2 mph
60 mph65.1 mph+5.1 mph
65 mph70.5 mph+5.5 mph
70 mph75.9 mph+5.9 mph
75 mph81.3 mph+6.3 mph
80 mph86.7 mph+6.7 mph

Each size on its own

Questions

Which is bigger, 285/25R21 or 285/35R21?
285/35R21 is taller by 2.24 inches (28.85" vs 26.61"). 285/25R21 is the same width.
Can I replace 285/25R21 with 285/35R21?
It is not recommended without checking carefully. The diameter difference is +8.4%, 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 285/35R21 change my speedometer?
When your speedometer reads 60 mph with 285/35R21 fitted (calibrated for 285/25R21), your real speed is 65.1 mph. Your odometer will under-count miles by about 8.4%.
Will 285/35R21 lift my vehicle?
Ride height changes by half the diameter difference: +1.12 inches of ground clearance at the axle.

Other comparisons