Tire Size Box

325/25R21 vs 325/35R21

325/35R21 compared with 325/25R21

+9.3% diameter, 0.0" width

325/35R21 is 29.96" tall vs 27.40". More than the 3% rule of thumb, so check carefully before switching.

27.4"21" rim3.2"12.8" wide
325/25R21 (solid) compared with 325/35R21 (dashed outline), drawn to scale

With 325/35R21 tires, when your speedometer says 60 mph you are really going

65.6 mph

325/35R21 is +2.56 inches (+9.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/25R21325/35R21Difference%
Overall diameter27.40"29.96"+2.56"+9.3%
Section width12.80"12.80"0.00"0.0%
Sidewall height3.20"4.48"+1.28"+40.0%
Circumference86.07"94.11"+8.04"+9.3%
Revolutions per mile736.1673.2−62.9−8.5%

Speedometer difference

If your vehicle came with 325/25R21 and you fit 325/35R21, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.9 mph+1.9 mph
30 mph32.8 mph+2.8 mph
40 mph43.7 mph+3.7 mph
50 mph54.7 mph+4.7 mph
60 mph65.6 mph+5.6 mph
65 mph71.1 mph+6.1 mph
70 mph76.5 mph+6.5 mph
75 mph82.0 mph+7.0 mph
80 mph87.5 mph+7.5 mph

Each size on its own

Questions

Which is bigger, 325/25R21 or 325/35R21?
325/35R21 is taller by 2.56 inches (29.96" vs 27.40"). 325/25R21 is the same width.
Can I replace 325/25R21 with 325/35R21?
It is not recommended without checking carefully. The diameter difference is +9.3%, 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 325/35R21 change my speedometer?
When your speedometer reads 60 mph with 325/35R21 fitted (calibrated for 325/25R21), your real speed is 65.6 mph. Your odometer will under-count miles by about 9.3%.
Will 325/35R21 lift my vehicle?
Ride height changes by half the diameter difference: +1.28 inches of ground clearance at the axle.

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