They refer to the same physical size, but ZR indicates a high-speed-rated tyre construction. What matters for road use is the actual speed rating letter (for example W or Y) and the load index shown on the sidewall, which must meet or exceed your car manufacturer’s specification.

It may not be a like-for-like swap because the overall rolling diameter and sidewall height differ, which can affect speedometer accuracy, ride comfort and clearance around the arches and suspension. Check your vehicle handbook or door pillar placard first, and only move to 235/40 R17 if it is an approved size for your exact model and axle.

Start with the exact load index and speed rating listed on your tyre placard or handbook, then match those values when filtering products. This size is often offered with several ratings, so choosing the correct one ensures legal compliance, the right carrying capacity and the handling your vehicle was designed for.

Some vehicles that use this size specify XL to support higher axle loads and maintain stability with a shorter 40 profile sidewall. If your current tyres show XL (or Reinforced) on the sidewall, replace them with the same specification, and set pressures to the vehicle’s recommended values.

Summer tyres suit warm-weather driving and deliver the most precise response, while winter tyres improve traction and braking in cold conditions and snow. All-season tyres are a strong choice for mixed UK weather if you want one set year-round, and you can compare options in 235/40 R17 by wet grip label, noise rating and brand to fit your driving style.