It describes the tyre’s size and construction: 255 is the width in millimetres, 50 is the sidewall height as a percentage of the width, R means radial construction, and 20 is the wheel diameter in inches. When buying a replacement, also match the load index and speed rating shown next to the size on your current tyre or in the vehicle handbook.
Usually not without checking approval, because the overall rolling diameter changes, which can affect speedometer accuracy, ground clearance and wheel-arch clearance. If your vehicle has alternative approved sizes, they will be listed on the door placard or in the handbook. If 255/55 R20 is not listed, stick with 255/50 R20 or speak to a qualified fitter before changing.
Use the exact load index and speed rating specified for your vehicle, as this size is often fitted to heavier SUVs and EVs that may require higher load ratings or XL (extra load) tyres. You can find the required ratings on the tyre sidewall, the driver’s door placard, or in the handbook. Choose tyres that meet or exceed the required load index and meet the required speed rating.
Yes - many manufacturers offer winter and all-season tyres in 255/50 R20, alongside summer patterns. For winter use, look for the 3PMSF (three-peak mountain snowflake) marking for tested snow performance, and for all-season consider 3PMSF models if you drive in colder conditions. Selecting the right season type helps match the tyre to your typical temperatures and roads.
If only two tyres are being replaced, fit the matching pair on the same axle to keep grip and handling consistent, and many fitters recommend putting the newest tyres on the rear. For AWD systems, replacing all four is often preferred when tread depths differ significantly, as uneven rolling circumference can put extra strain on the drivetrain. Check your vehicle guidance, then choose two or four tyres based on tread wear and drivetrain type.
