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Tire size

255/45R21 tire size: dimensions explained

Factory size on the Porsche Macan Electric. Below are the dimensions calculated from the size marking itself. Your vehicle's correct size, load index and speed rating are on the placard in the driver's door jamb; check it before buying.

MeasurementMetricImperial
Section width255 mm10.04 in
Sidewall height114.8 mm4.52 in
Overall diameter762.9 mm30.04 in
Wheel diameter533.4 mm21 in
Circumference2398 mm94.4 in
Revolutions per mile671

Calculated values: diameter = wheel + 2 × (width × aspect ratio). Real tires vary slightly by brand and model.

Reading the marking

255 is the section width in millimetres, 45 is the sidewall height as a percentage of that width, R means radial construction, and 21 is the wheel diameter in inches. A passenger (P or Euro-metric) tire and an LT tire in the same size are not interchangeable without checking load requirements.

Compare 255/45R21 with another size →

255/45R21 tires at Tire Rack

All-season

TireLoad/speedPrice per tire
Michelin Primacy A/S
Standard Touring All-Season		XL 106W$444.99View at Tire Rack
Michelin Pilot Sport All Season 4
Ultra High Performance All-Season		XL 106V$473.59View at Tire Rack

Highway / touring

TireLoad/speedPrice per tire
Continental CrossContact RX
Crossover/SUV Touring All-Season		XL 106V$407.04View at Tire Rack
Pirelli Scorpion MS
Crossover/SUV Touring All-Season		XL 106V$580.36View at Tire Rack

Summer performance

TireLoad/speedPrice per tire
Bridgestone Potenza Sport
Max Performance Summer		XL 106Y$139.00View at Tire Rack
Bridgestone Turanza T005
Grand Touring Summer		XL 106W$174.67View at Tire Rack

Winter

TireLoad/speedPrice per tire
Michelin X-Ice Snow SUV
Light Truck/SUV Studless Ice & Snow Truck		XL 106H$284.44View at Tire Rack
Michelin Pilot Alpin 5 SUV
Light Truck/SUV Performance Snow Truck		XL 106V$327.20View at Tire Rack

Showing the lowest-priced in-stock options in each category from 17 255/45R21 tires in Tire Rack's feed, sorted by price only. We don't rank by commission. Match or exceed the load index and speed rating on your placard.

Affiliate links: if you buy through a Tire Rack link, RightTread may earn a commission through CJ. It doesn't change your price. Prices are Tire Rack's per-tire prices from Tire Rack's product feed as of Nov 7, 2026, 9:19 PM PT. Prices change, so confirm on Tire Rack before you buy. Disclosure

Other sizes