What is the diameter of a 305/30R21 tire?

A 305/30R21 tire has an overall diameter of 28.2 inches (716.3mm).

How many revolutions per mile does a 305/30R21 tire make?

A 305/30R21 tire makes approximately 715 revolutions per mile.

What rim width is recommended for 305/30R21 tires?

The recommended wheel rim width for a 305/30R21 tire is 7.6" - 10.7".

305/30R21

Standard Metric

Factory Specs, Physical Dimensions & Compatible Vehicle Applications

Factory Spec Overview

The 305/30R21 tire size features an overall diameter of 28.2 inches, a section width of 12.0 inches (305mm), and rotates 715 times per mile. It is a standard factory tire fitment on 135+ vehicle models including Audi RS e-tron GT, Mercedes-Benz SL63 S E Performance AMG.

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Physical Dimensions & Specs

Overall Diameter

28.2"

716.3 mm

Section Width

305 mm

12.01" wide

Sidewall Height

3.6"

91.4 mm (30% aspect)

Revolutions / Mile

715

Circumference: 88.61"

Rim Diameter

21"

Wheel size

Recommended Rim Width

7.6" - 10.7"

Optimal rim width range

Speedometer & Alternate Size Calculator

Testing an alternate size for your vehicle? Compare 305/30R21 against any proposed tire size below:

Popular Comparisons:

Tire 1 (Stock / Base)305/30R21

Section Width (mm)

Aspect Ratio (%)

Rim Diameter (in)

Wheel Width (in)

Offset ET (mm)

Overall Height:28.2"

Sidewall:3.6"

Revs/Mile:715

Tire 2 (New / Compare)245/60R18

Section Width (mm)

Aspect Ratio (%)

Rim Diameter (in)

Wheel Width (in)

Offset ET (mm)

Overall Height:29.6"

Sidewall:5.8"

Revs/Mile:682

Visual Tire & Wheel Comparison

Speedometer Variance

+4.9%At 60 mph reading, actual speed is 62.9 mph

Indicated	Actual Speed	Diff
20 mph	21.0 mph	+1.0 mph
30 mph	31.5 mph	+1.5 mph
45 mph	47.2 mph	+2.2 mph
60 mph	62.9 mph	+2.9 mph
75 mph	78.6 mph	+3.6 mph
90 mph	94.4 mph	+4.4 mph

Fender & Suspension Clearance

Fitment Status: MODERATE RISK

Flush fitment. Extends 17.7mm outwards. Check wheel arch clearance under full suspension compression.

Inner Strut Space:7.7mm LESS clearance

Outer Fender Push:Extends 17.7mm further out

Ride Height Delta:+0.69" ground clearance

Vehicles That Fit 305/30R21 (135+ Models)

Factory standard and optional vehicle fitments utilizing 305/30R21 tires:

Year	Make & Model	Trim / Variant	Lookup Specs
2024	Audi RS e-tron GT	RS e-tron GT	View 2024 RS e-tron GT ›
2025	Audi RS e-tron GT	RS e-tron GT	View 2025 RS e-tron GT ›
2025	Mercedes-Benz SL63 S E Performance AMG	SL63 S E Performance AMG	View 2025 SL63 S E Performance AMG ›
2020	Porsche 911	Carrera S, 2D Coupe	View 2020 911 ›
2020	Porsche 911	Carrera 4S, 2D Coupe	View 2020 911 ›
2020	Porsche 911	Carrera 4S, 2D Convertible	View 2020 911 ›
2020	Porsche 911	Carrera S, 2D Convertible	View 2020 911 ›
2020	Porsche Taycan	Turbo	View 2020 Taycan ›
2020	Porsche Taycan	Turbo S	View 2020 Taycan ›
2020	Porsche Taycan	4S	View 2020 Taycan ›
2021	Porsche 911	Carrera 4S, 2D Convertible, Automatic DCT Trans	View 2021 911 ›
2021	Porsche 911	Carrera 4S, 2D Convertible, Standard Trans	View 2021 911 ›
2021	Porsche 911	Carrera 4S, 2D Coupe, Automatic DCT Trans	View 2021 911 ›
2021	Porsche 911	Carrera 4S, 2D Coupe, Standard Trans	View 2021 911 ›
2021	Porsche 911	Carrera S, 2D Convertible, Automatic DCT Trans	View 2021 911 ›
2021	Porsche 911	Carrera S, 2D Coupe, Automatic DCT Trans	View 2021 911 ›
2021	Porsche 911	Carrera S, 2D Convertible, Standard Trans	View 2021 911 ›
2021	Porsche 911	Carrera S, 2D Coupe, Standard Trans	View 2021 911 ›
2021	Porsche 911	Targa 4S Heritage Design Ed., Standard Trans	View 2021 911 ›
2021	Porsche 911	Targa 4S Heritage Design Ed., Automatic DCT Trans	View 2021 911 ›
2021	Porsche 911	Targa 4S, Automatic DCT Trans	View 2021 911 ›
2021	Porsche 911	Targa 4S, Standard Trans	View 2021 911 ›
2021	Porsche Taycan	4 Cross Turismo	View 2021 Taycan ›
2021	Porsche Taycan	4S Cross Turismo	View 2021 Taycan ›
2021	Porsche Taycan	Base	View 2021 Taycan ›
2021	Porsche Taycan	Turbo	View 2021 Taycan ›
2021	Porsche Taycan	4S	View 2021 Taycan ›
2021	Porsche Taycan	Turbo S	View 2021 Taycan ›
2022	Porsche 911	Carrera 4 GTS, 2D Convertible, Automatic DCT Trans	View 2022 911 ›
2022	Porsche 911	Carrera 4 GTS, 2D Coupe, Automatic DCT Trans	View 2022 911 ›
2022	Porsche 911	Carrera 4 GTS, 2D Convertible, Standard Trans	View 2022 911 ›
2022	Porsche 911	Carrera 4 GTS, 2D Coupe, Standard Trans	View 2022 911 ›
2022	Porsche 911	Carrera 4S, 2D Convertible, Standard Trans	View 2022 911 ›
2022	Porsche 911	Carrera 4S, 2D Convertible, Automatic DCT Trans	View 2022 911 ›
2022	Porsche 911	Carrera 4S, 2D Coupe, Automatic DCT Trans	View 2022 911 ›
2022	Porsche 911	Carrera 4S, 2D Coupe, Standard Trans	View 2022 911 ›
2022	Porsche 911	Carrera GTS, 2D Convertible, Automatic DCT Trans	View 2022 911 ›
2022	Porsche 911	Carrera GTS, 2D Convertible, Standard Trans	View 2022 911 ›
2022	Porsche 911	Carrera GTS, 2D Coupe, Automatic DCT Trans	View 2022 911 ›
2022	Porsche 911	Carrera GTS, 2D Coupe, Standard Trans	View 2022 911 ›
2022	Porsche 911	Carrera S, 2D Convertible, Automatic DCT Trans	View 2022 911 ›
2022	Porsche 911	Carrera S, 2D Convertible, Standard Trans	View 2022 911 ›
2022	Porsche 911	Carrera S, 2D Coupe, Automatic DCT Trans	View 2022 911 ›
2022	Porsche 911	Carrera S, 2D Coupe, Standard Trans	View 2022 911 ›
2022	Porsche 911	Targa 4 GTS, Automatic DCT Trans	View 2022 911 ›
2022	Porsche 911	Targa 4 GTS, Standard Trans	View 2022 911 ›
2022	Porsche 911	Targa 4S, Automatic DCT Trans	View 2022 911 ›
2022	Porsche 911	Targa 4S, Standard Trans	View 2022 911 ›
2022	Porsche Taycan	4 Cross Turismo	View 2022 Taycan ›
2022	Porsche Taycan	4S	View 2022 Taycan ›
2022	Porsche Taycan	4S Cross Turismo	View 2022 Taycan ›
2022	Porsche Taycan	Base	View 2022 Taycan ›
2022	Porsche Taycan	GTS	View 2022 Taycan ›
2022	Porsche Taycan	GTS Sport Turismo	View 2022 Taycan ›
2022	Porsche Taycan	Turbo	View 2022 Taycan ›
2022	Porsche Taycan	Turbo Cross Turismo	View 2022 Taycan ›
2022	Porsche Taycan	Turbo S	View 2022 Taycan ›
2022	Porsche Taycan	Turbo S Cross Turismo	View 2022 Taycan ›
2023	Porsche 911	Carrera 4 GTS, 2D Convertible, Automatic DCT Trans	View 2023 911 ›
2023	Porsche 911	Carrera 4 GTS, 2D Convertible, Standard Trans	View 2023 911 ›
2023	Porsche 911	Carrera 4 GTS, 2D Coupe, Automatic DCT Trans	View 2023 911 ›
2023	Porsche 911	Carrera 4 GTS, 2D Coupe, Standard Trans	View 2023 911 ›
2023	Porsche 911	Carrera 4S, 2D Convertible, Automatic DCT Trans	View 2023 911 ›
2023	Porsche 911	Carrera 4S, 2D Convertible, Standard Trans	View 2023 911 ›
2023	Porsche 911	Carrera 4S, 2D Coupe, Automatic DCT Trans	View 2023 911 ›
2023	Porsche 911	Carrera 4S, 2D Coupe, Standard Trans	View 2023 911 ›
2023	Porsche 911	Carrera GTS, 2D Convertible, Automatic DCT Trans	View 2023 911 ›
2023	Porsche 911	Carrera GTS, 2D Convertible, Standard Trans	View 2023 911 ›
2023	Porsche 911	Carrera GTS, 2D Coupe, Automatic DCT Trans	View 2023 911 ›
2023	Porsche 911	Carrera GTS, 2D Coupe, Standard Trans	View 2023 911 ›
2023	Porsche 911	Carrera S, 2D Convertible, Automatic DCT Trans	View 2023 911 ›
2023	Porsche 911	Carrera S, 2D Convertible, Standard Trans	View 2023 911 ›
2023	Porsche 911	Carrera S, 2D Coupe, Automatic DCT Trans	View 2023 911 ›
2023	Porsche 911	Carrera S, 2D Coupe, Standard Trans	View 2023 911 ›
2023	Porsche 911	Carrera T, Automatic DCT Trans	View 2023 911 ›
2023	Porsche 911	Carrera T, Standard Trans	View 2023 911 ›
2023	Porsche 911	Edition 50 Yrs Porsche Design, Automatic DCT Trans	View 2023 911 ›
2023	Porsche 911	Edition 50 Yrs Porsche Design, Standard Trans	View 2023 911 ›
2023	Porsche 911	Targa 4 GTS, Automatic DCT Trans	View 2023 911 ›
2023	Porsche 911	Targa 4 GTS, Standard Trans	View 2023 911 ›
2023	Porsche 911	Targa 4S, Automatic DCT Trans	View 2023 911 ›
2023	Porsche 911	Targa 4S, Standard Trans	View 2023 911 ›
2023	Porsche Taycan	4 Cross Turismo	View 2023 Taycan ›
2023	Porsche Taycan	4S	View 2023 Taycan ›
2023	Porsche Taycan	4S Cross Turismo	View 2023 Taycan ›
2023	Porsche Taycan	Base	View 2023 Taycan ›
2023	Porsche Taycan	GTS	View 2023 Taycan ›
2023	Porsche Taycan	GTS Sport Turismo	View 2023 Taycan ›
2023	Porsche Taycan	Turbo	View 2023 Taycan ›
2023	Porsche Taycan	Turbo Cross Turismo	View 2023 Taycan ›
2023	Porsche Taycan	Turbo S	View 2023 Taycan ›
2023	Porsche Taycan	Turbo S Cross Turismo	View 2023 Taycan ›
2024	Porsche 911	Carrera 4 GTS, 2D Coupe, Standard Trans	View 2024 911 ›
2024	Porsche 911	Carrera 4S, 2D Convertible, Automatic DCT Trans	View 2024 911 ›
2024	Porsche 911	Carrera 4 GTS, 2D Convertible, Standard Trans	View 2024 911 ›
2024	Porsche 911	Carrera 4 GTS, 2D Convertible, Automatic DCT Trans	View 2024 911 ›
2024	Porsche 911	Carrera 4S, 2D Convertible, Standard Trans	View 2024 911 ›
2024	Porsche 911	Carrera GTS, 2D Convertible, Automatic DCT Trans	View 2024 911 ›
2024	Porsche 911	Carrera 4S, 2D Coupe, Automatic DCT Trans	View 2024 911 ›
2024	Porsche 911	Carrera 4 GTS, 2D Coupe, Automatic DCT Trans	View 2024 911 ›
2024	Porsche 911	Carrera GTS, 2D Convertible, Standard Trans	View 2024 911 ›
2024	Porsche 911	Carrera GTS, 2D Coupe, Automatic DCT Trans	View 2024 911 ›
2024	Porsche 911	Carrera 4S, 2D Coupe, Standard Trans	View 2024 911 ›
2024	Porsche 911	Carrera S, 2D Convertible, Automatic DCT Trans	View 2024 911 ›
2024	Porsche 911	Carrera GTS, 2D Coupe, Standard Trans	View 2024 911 ›
2024	Porsche 911	Carrera S, 2D Convertible, Standard Trans	View 2024 911 ›
2024	Porsche 911	Carrera S, 2D Coupe, Automatic DCT Trans	View 2024 911 ›
2024	Porsche 911	Carrera S, 2D Coupe, Standard Trans	View 2024 911 ›
2024	Porsche 911	Carrera T, Automatic DCT Trans	View 2024 911 ›
2024	Porsche 911	Carrera T, Standard Trans	View 2024 911 ›
2024	Porsche 911	Targa 4 GTS, Automatic DCT Trans	View 2024 911 ›
2024	Porsche 911	Targa 4 GTS, Standard Trans	View 2024 911 ›
2024	Porsche 911	Targa 4S, Automatic DCT Trans	View 2024 911 ›
2024	Porsche 911	Targa 4S, Standard Trans	View 2024 911 ›
2024	Porsche Taycan	4 Cross Turismo	View 2024 Taycan ›
2024	Porsche Taycan	4S	View 2024 Taycan ›
2024	Porsche Taycan	4S Cross Turismo	View 2024 Taycan ›
2024	Porsche Taycan	Base	View 2024 Taycan ›
2024	Porsche Taycan	GTS	View 2024 Taycan ›
2024	Porsche Taycan	GTS Sport Turismo	View 2024 Taycan ›
2024	Porsche Taycan	Turbo	View 2024 Taycan ›
2024	Porsche Taycan	Turbo Cross Turismo	View 2024 Taycan ›
2024	Porsche Taycan	Turbo S	View 2024 Taycan ›
2024	Porsche Taycan	Turbo S Cross Turismo	View 2024 Taycan ›
2025	Porsche 911	Carrera, 2D Convertible	View 2025 911 ›
2025	Porsche Taycan	4	View 2025 Taycan ›
2025	Porsche Taycan	4 Cross Turismo	View 2025 Taycan ›
2025	Porsche Taycan	4S	View 2025 Taycan ›
2025	Porsche Taycan	4S Cross Turismo	View 2025 Taycan ›
2025	Porsche Taycan	Base	View 2025 Taycan ›
2025	Porsche Taycan	Turbo	View 2025 Taycan ›
2025	Porsche Taycan	Turbo Cross Turismo	View 2025 Taycan ›
2025	Porsche Taycan	Turbo GT	View 2025 Taycan ›
2025	Porsche Taycan	Turbo S	View 2025 Taycan ›
2025	Porsche Taycan	Turbo S Cross Turismo	View 2025 Taycan ›