Tire Size Box

275/30R21 vs 275/35R21

275/35R21 compared with 275/30R21

+3.9% diameter, 0.0" width

275/35R21 is 28.58" tall vs 27.50". More than the 3% rule of thumb, so check carefully before switching.

27.5"21" rim3.2"10.8" wide
275/30R21 (solid) compared with 275/35R21 (dashed outline), drawn to scale

With 275/35R21 tires, when your speedometer says 60 mph you are really going

62.4 mph

275/35R21 is +1.08 inches (+3.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/30R21275/35R21Difference%
Overall diameter27.50"28.58"+1.08"+3.9%
Section width10.83"10.83"0.00"0.0%
Sidewall height3.25"3.79"+0.54"+16.7%
Circumference86.38"89.78"+3.40"+3.9%
Revolutions per mile733.5705.7−27.8−3.8%

Speedometer difference

If your vehicle came with 275/30R21 and you fit 275/35R21, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.2 mph+1.2 mph
40 mph41.6 mph+1.6 mph
50 mph52.0 mph+2.0 mph
60 mph62.4 mph+2.4 mph
65 mph67.6 mph+2.6 mph
70 mph72.8 mph+2.8 mph
75 mph78.0 mph+3.0 mph
80 mph83.2 mph+3.2 mph

Each size on its own

Questions

Which is bigger, 275/30R21 or 275/35R21?
275/35R21 is taller by 1.08 inches (28.58" vs 27.50"). 275/30R21 is the same width.
Can I replace 275/30R21 with 275/35R21?
It is not recommended without checking carefully. The diameter difference is +3.9%, 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 275/35R21 change my speedometer?
When your speedometer reads 60 mph with 275/35R21 fitted (calibrated for 275/30R21), your real speed is 62.4 mph. Your odometer will under-count miles by about 3.9%.
Will 275/35R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.54 inches of ground clearance at the axle.

Other comparisons