Tire Size Box

305/30R21 vs 295/35R21

295/35R21 compared with 305/30R21

+3.3% diameter, −0.4" width

295/35R21 is 29.13" tall vs 28.20". More than the 3% rule of thumb, so check carefully before switching.

28.2"21" rim3.6"12.0" wide
305/30R21 (solid) compared with 295/35R21 (dashed outline), drawn to scale

With 295/35R21 tires, when your speedometer says 60 mph you are really going

62.0 mph

295/35R21 is +0.93 inches (+3.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

305/30R21295/35R21Difference%
Overall diameter28.20"29.13"+0.93"+3.3%
Section width12.01"11.61"−0.39"−3.3%
Sidewall height3.60"4.06"+0.46"+12.8%
Circumference88.61"91.51"+2.91"+3.3%
Revolutions per mile715.1692.4−22.7−3.2%

Speedometer difference

If your vehicle came with 305/30R21 and you fit 295/35R21, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.0 mph+1.0 mph
40 mph41.3 mph+1.3 mph
50 mph51.6 mph+1.6 mph
60 mph62.0 mph+2.0 mph
65 mph67.1 mph+2.1 mph
70 mph72.3 mph+2.3 mph
75 mph77.5 mph+2.5 mph
80 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 305/30R21 or 295/35R21?
295/35R21 is taller by 0.93 inches (29.13" vs 28.20"). 305/30R21 is wider by 0.39 inches.
Can I replace 305/30R21 with 295/35R21?
It is not recommended without checking carefully. The diameter difference is +3.3%, 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 295/35R21 change my speedometer?
When your speedometer reads 60 mph with 295/35R21 fitted (calibrated for 305/30R21), your real speed is 62.0 mph. Your odometer will under-count miles by about 3.3%.
Will 295/35R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.46 inches of ground clearance at the axle.

Other comparisons