255/45R21
Standard MetricFactory Specs, Physical Dimensions & Compatible Vehicle Applications
The 255/45R21 tire size features an overall diameter of 30.04 inches, a section width of 10.0 inches (255mm), and rotates 671 times per mile. It is a standard factory tire fitment on 1+ vehicle models including Audi SQ6 e-tron.
Physical Dimensions & Specs
Overall Diameter
30.04"
763.0 mmSection Width
255 mm
10.04" wideSidewall Height
4.52"
114.8 mm (45% aspect)Revolutions / Mile
671
Circumference: 94.36"Rim Diameter
21"
Wheel sizeRecommended Rim Width
6.4" - 8.9"
Optimal rim width rangeWhere to Buy & Install 255/45R21 Tires
Looking for 255/45R21 tires? Skip hauling tires in your car—choose direct delivery to a local certified shop or doorstep delivery:
Tire Rack
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Amazon Automotive
Fast doorstep shipping for DIYers or bringing to your own shop.
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Speedometer & Alternate Size Calculator
Testing an alternate size for your vehicle? Compare 255/45R21 against any proposed tire size below:
Visual Tire & Wheel Comparison
Speedometer Variance
| Indicated | Actual Speed | Diff |
|---|---|---|
| 20 mph | 19.7 mph | -0.3 mph |
| 30 mph | 29.5 mph | -0.5 mph |
| 45 mph | 44.3 mph | -0.7 mph |
| 60 mph | 59.1 mph | -0.9 mph |
| 75 mph | 73.8 mph | -1.2 mph |
| 90 mph | 88.6 mph | -1.4 mph |
Fender & Suspension Clearance
Flush fitment. Extends 17.7mm outwards. Check wheel arch clearance under full suspension compression.
Vehicles That Fit 255/45R21 (1+ Models)
Factory standard and optional vehicle fitments utilizing 255/45R21 tires: