275/40R21 is a tire size notation. It describes geometry but does not establish the load, speed, tire class, wheel approval or fit of a particular replacement.
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How to read this size
- Nominal width: 275 mm
- Aspect ratio: 40 %
- Wheel diameter: 21.0 in
- Calculated nominal diameter: 753.4 mm
Calculated nominal diameter is an arithmetic estimate from the size code; actual product measurements vary.
Before ordering tires
Read the driver-door tire placard. Match the installed wheel, axle, tire class, load index, speed rating and any OE marking. The size alone cannot approve a replacement SKU. Tire-sidewall maximum pressure is not your vehicle’s cold inflation pressure.
Vehicles recorded with this size
| Model year and vehicle | Trim / option | Axle | Service |
|---|---|---|---|
| 2025 Acura MDX | Type S Advance | front_rear | Not documented |
| 2025 BMW X5 | M60i | front | Not documented |
| 2025 BMW X5 | sDrive40i | front | Not documented |
| 2025 BMW X5 | xDrive40i | front | Not documented |
| 2025 BMW X5 | xDrive50e | front | Not documented |
| 2025 Cadillac OPTIQ | Luxury 1 | unspecified | Not documented |
| 2025 Cadillac OPTIQ | Luxury 2 | unspecified | Not documented |
| 2025 Cadillac OPTIQ | Sport 1 | unspecified | Not documented |
| 2025 Cadillac OPTIQ | Sport 2 | unspecified | Not documented |
| 2017 Volkswagen Touareg | V6 Executive | unspecified | Not documented |
Exact product variants in research
No source-backed rows are available for this exact selection.
Explore 275/40R21 tires on Amazon
Amazon search results may mix tire classes, load and speed ratings, OE markings and package quantities. Match the full requirement on your actual vehicle before ordering.
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Search 275/40R21 tires on AmazonCompare sizes with the tire size calculator. It is an educational geometry comparison, not a fitment ruling.
Sources and scope
- American Honda / Acura — 2025 Acura MDX Specifications & Features (checked 2026-11-01)
- Goodyear — 2025 BMW X5 tire size by trim (checked 2026-11-01)
- Goodyear — Find 2025 Cadillac OPTIQ Tires | Goodyear (checked 2026-11-01)
- Goodyear — Find 2017 Volkswagen Touareg Tires | Goodyear (checked 2026-11-01)
Research checked November 2, 2026. A source-observed size is not final product fitment. Confirm the actual vehicle and current manufacturer guidance.