It needs a 21 inch rim and the correct wheel width. As a guide, 265/30 R21 is typically suited to around a 9.0 to 10.5 inch wide wheel, with 9.5 inches often considered ideal. Also confirm the overall rolling radius matches your current fitment to avoid speedometer and clearance issues.
Match the load index and speed rating to the values shown on your door placard or handbook, not just what is currently fitted. Many 265/30 R21 options are high-speed rated (often Y or (Y)) and may be XL (reinforced) due to the low sidewall and higher wheel loads. If you are between two options, choose the one that meets or exceeds the vehicle requirement.
Some manufacturers do offer run-flat tyres in 265/30 R21, but availability depends on brand and specific pattern. Run-flats usually ride firmer and can be noisier, which is more noticeable with a 30-profile sidewall. If your car was not designed for run-flats, check wheel compatibility and consider whether a standard tyre plus repair kit better suits your driving.
Yes, this size is often used in staggered setups, but you should follow the vehicle manufacturer or wheel supplier recommendation. Keep the same tyre model across each axle, and avoid mixing construction types or markedly different tread designs front to rear. Common pairings use a wider rear size such as 295/30 R21 or 305/30 R21, provided the rolling circumference remains within tolerance.
Most tyres in 265/30 R21 are summer performance patterns because the size is typically fitted to higher-powered vehicles on 21 inch wheels. Winter and all-season choices can be limited, and the low sidewall is less forgiving on cold, rough roads. If you need better cold-weather capability, consider whether your vehicle supports an approved winter wheel and tyre package in a smaller diameter.