Tire Size Box

235/25R21 vs 235/35R21

235/35R21 compared with 235/25R21

+7.2% diameter, 0.0" width

235/35R21 is 27.48" tall vs 25.63". More than the 3% rule of thumb, so check carefully before switching.

25.6"21" rim2.3"9.3" wide
235/25R21 (solid) compared with 235/35R21 (dashed outline), drawn to scale

With 235/35R21 tires, when your speedometer says 60 mph you are really going

64.3 mph

235/35R21 is +1.85 inches (+7.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

235/25R21235/35R21Difference%
Overall diameter25.63"27.48"+1.85"+7.2%
Section width9.25"9.25"0.00"0.0%
Sidewall height2.31"3.24"+0.93"+40.0%
Circumference80.51"86.32"+5.81"+7.2%
Revolutions per mile787.0734.0−53.0−6.7%

Speedometer difference

If your vehicle came with 235/25R21 and you fit 235/35R21, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.4 mph+1.4 mph
30 mph32.2 mph+2.2 mph
40 mph42.9 mph+2.9 mph
50 mph53.6 mph+3.6 mph
60 mph64.3 mph+4.3 mph
65 mph69.7 mph+4.7 mph
70 mph75.1 mph+5.1 mph
75 mph80.4 mph+5.4 mph
80 mph85.8 mph+5.8 mph

Each size on its own

Questions

Which is bigger, 235/25R21 or 235/35R21?
235/35R21 is taller by 1.85 inches (27.48" vs 25.63"). 235/25R21 is the same width.
Can I replace 235/25R21 with 235/35R21?
It is not recommended without checking carefully. The diameter difference is +7.2%, 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 235/35R21 change my speedometer?
When your speedometer reads 60 mph with 235/35R21 fitted (calibrated for 235/25R21), your real speed is 64.3 mph. Your odometer will under-count miles by about 7.2%.
Will 235/35R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.93 inches of ground clearance at the axle.

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