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Tire Size Calculator
Tire Size Conversion
Convert between metric and inch tire sizes
Calculate Tire Dimensions
Calculate tire diameter and circumference
Compare Tire Sizes
Compare specifications of different tires
Tire Speed Rating & Load Index
Find your tire's specifications
Tire Specifications
How to Use the Tire Size Calculator
Tire Conversion Calculator
This tool converts between metric tire size format (like 195/55R16) and calculates detailed measurements. Enter the tire width, aspect ratio, rim diameter, and tire type to get converted specifications.
Tire Dimensions Calculator
Calculate the exact diameter and circumference of your tires based on width, aspect ratio, and rim diameter. These measurements are crucial for speedometer accuracy and vehicle performance.
Tire Comparison Tool
Compare two different tire sizes side by side. See the differences in diameter, circumference, width, and sidewall height to determine compatibility with your vehicle.
Speed Rating Lookup
Find information about tire speed ratings and load indices. These ratings indicate the maximum speed the tire can safely handle and the maximum weight it can carry.
Understanding Tire Sizes
Tire Size Format Explained
A typical tire size looks like: 195/55R16 87V
- 195: Tire width in millimeters (section width)
- 55: Aspect ratio - sidewall height as percentage of width (55% of 195mm = 107.25mm)
- R: Tire construction type (R = Radial, D = Diagonal)
- 16: Wheel rim diameter in inches
- 87: Load index (maximum weight per tire)
- V: Speed rating (maximum safe speed)
Tire Dimensions
Understanding tire measurements helps ensure proper fit and performance:
- Tire Diameter: Overall height of the tire when mounted. Affects speedometer accuracy and ground clearance.
- Tire Circumference: Distance around the tire. Used to calculate vehicle speed and odometer readings.
- Section Width: Actual width of the tire from sidewall to sidewall. Affects handling and fuel efficiency.
- Sidewall Height: Height of the rubber portion from rim to tread. Affects ride comfort and handling.
Speed Ratings
Speed ratings indicate the maximum speed a tire can safely handle:
| Rating | Maximum Speed (km/h) | Maximum Speed (mph) | Typical Use |
|---|---|---|---|
| N | 140 | 87 | Spare tires |
| P | 150 | 93 | Economy cars |
| Q | 160 | 100 | Economy cars |
| R | 170 | 106 | Standard cars |
| S | 180 | 112 | Standard cars |
| T | 190 | 118 | Standard/luxury cars |
| H | 210 | 130 | Sports cars |
| V | 240 | 149 | High-performance |
| Z | 300+ | 186+ | Super sports |
Load Index
The load index is a two or three-digit number that represents the maximum weight a tire can carry when properly inflated. For example, load index 95 means the tire can carry a maximum of 690 kg. Always use tires with a load index equal to or greater than your vehicle's requirements.
Tire Types
- All-Season Tires: Suitable for most driving conditions with moderate performance in winter and summer.
- Summer Tires: Optimized for warm weather with better handling and shorter braking distance.
- Winter Tires: Designed for snow and ice with better traction in cold temperatures.
- All-Terrain Tires: For SUVs and trucks, suitable for on and off-road use.
- Performance Tires: For sports cars, offering excellent grip and handling at high speeds.
Tire Maintenance & Safety Tips
Tire Pressure
- Check tire pressure monthly when tires are cold (at least 3 hours after driving)
- Proper inflation improves fuel efficiency by 3-5%
- Underinflated tires wear faster and generate more heat
- Overinflated tires reduce comfort and wear unevenly
- Find recommended pressure on the driver's door jamb or vehicle manual
Tire Rotation
- Rotate tires every 8,000-12,000 km to ensure even wear
- Front tires wear faster than rear tires
- Different rotation patterns for front-wheel, rear-wheel, and all-wheel drive vehicles
- Prolongs tire life by 10-20%
Tire Replacement
- Replace tires when tread depth reaches 1.6 mm (legal minimum)
- For safety, consider replacement at 3-4 mm depth
- Use the penny test: Insert a penny into the tread. If you can see the top of Lincoln's head, tread is too worn.
- Average tire lifespan: 3-5 years or 40,000-80,000 km
Safety Checks
- Inspect tires monthly for cracks, bulges, or uneven wear
- Check for punctures, cuts, or debris
- Monitor alignment if tires wear unevenly
- Balance tires every 20,000 km to prevent vibration
- Replace tires if you notice visible damage
Seasonal Considerations
- Winter: Switch to winter tires for better snow/ice traction below 7°C
- Summer: Summer tires provide better performance in warm conditions
- Storage: Store spare tires in a cool, dry place away from sunlight
- Pressure Adjustment: Tire pressure increases in hot weather, decreases in cold
Frequently Asked Questions
Can I use a different tire size than recommended?
Only if the new tire size is approved by your vehicle manufacturer. The overall diameter difference should not exceed 3%. Always check your vehicle manual or contact the manufacturer for approved tire sizes.
What does the load index number mean?
The load index is a two or three-digit code that indicates the maximum weight a tire can safely carry. For example, 95 means approximately 690 kg. Always use tires with at least the minimum load index your vehicle requires.
How do I read a tire sidewall?
Tire sidewalls contain size, load index, speed rating, manufacturing date, and other information. The format is Width/Aspect RatioType RimSize LoadIndex SpeedRating (e.g., 195/55R16 87V).
What is the difference between speed ratings?
Speed ratings indicate the maximum speed a tire can safely handle. They range from N (140 km/h) to Z (above 300 km/h). Using tires with lower ratings than recommended can be unsafe.
How often should I rotate my tires?
Rotate tires every 8,000-12,000 km or every 6 months. Front tires wear faster due to steering and braking forces. Rotation ensures even wear and extends tire life by 10-20%.
What does aspect ratio mean?
Aspect ratio is the sidewall height expressed as a percentage of tire width. For example, 55 means the sidewall is 55% of the tire width. Lower ratios provide better handling, higher ratios provide better comfort.
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