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215/70R16 vs 345/25R21 tire size comparison

215/70R16345/25R21

345/25R21 is 0.1 in (0.21%) shorter than 215/70R16 and 5.1 in wider. They fit different wheels: 215/70R16 a 16-inch wheel and 345/25R21 a 21-inch wheel.

215/70R16 and 345/25R21 side by side

-0.1 in / -0.21%215/70R16: 27.9 in tall, solid line345/25R21: 27.8 in tall, dashed line215/70R16Width 8.5 in (215 mm)Sidewall 5.9 in (151 mm)345/25R21Width 13.6 in (345 mm)Sidewall 3.4 in (86 mm)
215/70R16 is drawn with a solid line and 345/25R21 with a dashed line. In each drawing both tires are to the same scale; the tread shoulder and bead curves are simplified. The table below has the same numbers.
Dimensions of 215/70R16 and 345/25R21, with the difference (345/25R21 minus 215/70R16)
Measurement215/70R16345/25R21DifferenceDifference %
Section width8.5 in (215 mm)13.6 in (345 mm)+5.1 in (+130 mm)+60.47%
Sidewall height5.9 in (151 mm)3.4 in (86 mm)-2.5 in (-65 mm)-42.69%
Wheel (rim) diameter16.0 in (406 mm)21.0 in (533 mm)+5.0 in (+127 mm)+31.25%
Overall diameter27.9 in (707 mm)27.8 in (706 mm)-0.1 in (-1 mm)-0.21%
Circumference87.5 in (2222 mm)87.3 in (2218 mm)-0.2 in (-4 mm)-0.21%
Revolutions per mile724726+2+0.21%

Differences are 345/25R21 minus 215/70R16; percentages are relative to 215/70R16. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.

The overall diameter differs by 0.21%, which is within the common 3% rule of thumb.

The rule of thumb keeps a replacement size within about 3% of the original overall diameter. It covers diameter only. It is not a fit, load or safety check, because width, wheel diameter, load capacity and clearance matter too. Confirm any size change with your vehicle's owner's manual or a tire professional.

Speedometer difference

When the speedometer reads 60 mph on a vehicle built for 215/70R16, the actual speed on 345/25R21 is about 59.9 mph. When it reads 60 mph on a vehicle built for 345/25R21, the actual speed on 215/70R16 is about 60.1 mph. These figures assume the speedometer is accurate on the original size and use nominal dimensions, so treat them as estimates.

Actual speed for a given speedometer reading, 215/70R16 against 345/25R21
Speedometer readsActual on 345/25R21 (built for 215/70R16)Actual on 215/70R16 (built for 345/25R21)
20 mph20.0 mph20.0 mph
30 mph29.9 mph30.1 mph
40 mph39.9 mph40.1 mph
50 mph49.9 mph50.1 mph
60 mph59.9 mph60.1 mph
70 mph69.9 mph70.1 mph
80 mph79.8 mph80.2 mph

A common rule of thumb is to keep a replacement size within about 3% of the original overall diameter. Check the tire placard on the driver's door jamb and your owner's manual for the sizes your vehicle was built for. Confirm any size change with your vehicle's owner's manual or a tire professional.

Which vehicles use each size?

These vehicles list the size among their verified sizes, by trim. Open one to see all of its sizes.

Check it in the calculator

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Shop for 215/70R16 or 345/25R21 tires

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Other comparisons with 215/70R16

Side-by-side dimensions and speedometer difference for sizes close to 215/70R16 in overall diameter.

Other comparisons with 345/25R21

Side-by-side dimensions and speedometer difference for sizes close to 345/25R21 in overall diameter.

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