Tire Size Box

345/30R20 vs 345/35R20

345/35R20 compared with 345/30R20

+4.8% diameter, 0.0" width

345/35R20 is 29.51" tall vs 28.15". More than the 3% rule of thumb, so check carefully before switching.

28.1"20" rim4.1"13.6" wide
345/30R20 (solid) compared with 345/35R20 (dashed outline), drawn to scale

With 345/35R20 tires, when your speedometer says 60 mph you are really going

62.9 mph

345/35R20 is +1.36 inches (+4.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

345/30R20345/35R20Difference%
Overall diameter28.15"29.51"+1.36"+4.8%
Section width13.58"13.58"0.00"0.0%
Sidewall height4.07"4.75"+0.68"+16.7%
Circumference88.43"92.70"+4.27"+4.8%
Revolutions per mile716.5683.5−33.0−4.6%

Speedometer difference

If your vehicle came with 345/30R20 and you fit 345/35R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.0 mph+1.0 mph
30 mph31.4 mph+1.4 mph
40 mph41.9 mph+1.9 mph
50 mph52.4 mph+2.4 mph
60 mph62.9 mph+2.9 mph
65 mph68.1 mph+3.1 mph
70 mph73.4 mph+3.4 mph
75 mph78.6 mph+3.6 mph
80 mph83.9 mph+3.9 mph

Each size on its own

Questions

Which is bigger, 345/30R20 or 345/35R20?
345/35R20 is taller by 1.36 inches (29.51" vs 28.15"). 345/30R20 is the same width.
Can I replace 345/30R20 with 345/35R20?
It is not recommended without checking carefully. The diameter difference is +4.8%, 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 345/35R20 change my speedometer?
When your speedometer reads 60 mph with 345/35R20 fitted (calibrated for 345/30R20), your real speed is 62.9 mph. Your odometer will under-count miles by about 4.8%.
Will 345/35R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.68 inches of ground clearance at the axle.

Other comparisons