Can I use 185 65R15 instead of 175 65R15?
The short answer is that it isn’t automatic. An 185/65R15 tire is wider and has a slightly larger overall diameter than a 175/65R15, and whether it fits depends on your vehicle’s clearance, rim width, and the tire maker’s specifications.
Understanding what the numbers mean
Before considering a swap, it helps to decode what these size codes imply for fit and performance. The first number is the tire width in millimeters, the second is the aspect ratio (the sidewall height as a percentage of the width), the “R” denotes radial construction, and the final number is the wheel diameter in inches. A shift from 175/65R15 to 185/65R15 increases width by 10 mm and overall diameter by about 2 percent, which can affect clearance and speedometer readings.
Practical implications of size differences
Two key takeaways from the size change are that you’ll gain a bit of road contact, and your tire’s rolling circumference grows slightly. This matters for clearance within the wheel well and for the accuracy of instruments that rely on tire rotation counts, such as the speedometer and odometer.
Fit and clearance considerations
Before you decide, consider these practical checks to determine if a swap can work safely on your vehicle.
- The overall diameter will be about 2% larger, which can raise ride height slightly and alter gearing feel in some cars.
- Rim width compatibility matters: 185/65R15 tires generally require rims within a supported width range; confirm that your 15-inch wheel is within the tire maker’s recommended range for the 185/65R15 size.
- Clearance around fenders, suspension components, and brake assemblies: a wider tire can rub at full steering lock or under compression if clearance is tight.
- Load index and speed rating: ensure the 185 tire offers an equal or higher load capacity and speed rating to meet or exceed your original tire specifications.
- Manufacturer guidance and vehicle-specific limits: many manufacturers specify acceptable sizes; deviating from them can affect warranty and safety features.
- Professional confirmation: if you’re unsure, consult a tire specialist or your vehicle’s dealer to confirm fitment for your exact model and trim.
In practice, whether you can swap depends on the tolerance built into your car’s design. If the manufacturer allows it and you have adequate clearance, the change may be possible, but professional verification is essential to avoid clearance issues or sensor misreadings.
Speedometer, gearing and safety implications
Changing tire width and diameter affects how far your car travels with each wheel rotation, which can influence instrument readings and some safety systems. Expect about a 2% difference in speedometer and odometer readings when moving from 175/65R15 to 185/65R15, with the speedometer showing a lower speed than actual as your tires grow larger.
- Speedometer and odometer accuracy: roughly a 2% discrepancy, depending on the exact tire and vehicle; plan for a small adjustment in driving speed perception.
- Handling and steering feel: a wider tire can alter steering response and contact patch distribution, which may feel different on corners or rough surfaces.
- ABS/traction control considerations: most modern systems tolerate small changes in tire size, but significant deviations can affect performance; verify with a technician.
- Consistent performance across seasons: ensure the 185/65R15 is suitable for the climate and typical road conditions you encounter.
If you decide to proceed, be aware of these considerations and arrange a professional installation that includes proper balancing and alignment checks.
What to do next
To move forward safely, follow these steps to verify suitability and ensure proper installation.
- Consult your vehicle’s owner's manual and the door placard for the recommended tire sizes and any acceptable alternatives.
- Check the tire manufacturer’s specifications for the 185/65R15 size to confirm compatible rim widths for your wheels.
- Have a tire professional inspect clearance in the wheel well, especially at full turn and under suspension compression.
- After installation, have the wheel alignment checked and, if needed, recalibrate or account for speedometer changes.
- Monitor vehicle behavior and handling closely over the first few hundred miles and consult the shop if you notice rubbing, vibrations, or reduced braking efficiency.
Bottom line: swapping to 185/65R15 is a possible option for some vehicles but requires verification of fit, clearance, and specifications. If in doubt, staying with the original 175/65R15 or selecting a size explicitly approved by the vehicle manufacturer is the safer route.
Summary
Swapping from 175/65R15 to 185/65R15 can be acceptable on some cars but is not universally recommended. The wider tire is about 2% larger in diameter, which can affect clearance, speedometer accuracy, and handling. Always check manufacturer guidance, verify rim width compatibility, and have a professional confirm fitment and alignment before making the change. When in doubt, the safest choice is to stick with the factory-recommended size.
