How tall is a 305/40R20 tire?

A 305/40R20 has a nominal overall diameter of 29.6 inches (752 mm), calculated as the 20-inch wheel plus two sidewalls. This is the unloaded figure — a fitted tire sits fractionally shorter under the weight of the vehicle.

What wheel size does a 305/40R20 tire fit?

A 305/40R20 fits a wheel of 20 inches in diameter. The wheel also has to be within the rim width range the manufacturer publishes for this size, which is printed in the tire's spec sheet.

What do the numbers in 305/40R20 mean?

305 is the section width in millimetres. 40 is the aspect ratio — the sidewall is 40% of the width, so 122 mm here. R marks the construction (radial). 20 is the wheel diameter in inches.

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Size Dimensions & Specs

Tires Size 305/40R20

Dimensions, specs, and every size 305/40R20 tire currently in stock

Overall Height

29.6"

752 mm · calculated

Section Width

305 mm

12.01 inches

Sidewall Height

4.8"

122 mm · 40% profile

Wheel Diameter

20"

508.0 mm

305/40R20 Specifications

Read directly from the size code. Load index, speed rating, and rim width range vary by model.

Specification	Imperial	Metric
Section width	12.01 in	305 mm
Aspect ratio	40%	—
Sidewall height	4.8 in	122 mm
Overall diameter (calculated)	29.6 in	752 mm
Wheel / rim diameter	20 in	508.0 mm
Construction	Radial	—

What does 305/40R20 mean?

Reading the code on your sidewall

Section width

305 mm

The distance from sidewall to sidewall across the tire's widest point.

Aspect ratio

40% profile

The sidewall stands 40% of the section width, which is 122 mm on this size.

Construction (R)

Radial

The body plies run across the tire at right angles to the direction of travel.

Wheel diameter

20 in

Fits a wheel measuring 20 inches across.

305/40R20 Questions & Answers

Dimensions and fitment guidelines for size 305/40R20

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Tires Size 305/40R20

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305/40R20 Specifications

What does 305/40R20 mean?

305 mm

40% profile

Radial

20 in

305/40R20 Questions & Answers

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