Enter two tire sizes to compare. The calculator will automatically calculate diameter, circumference, sidewall height, revolutions per mile, and speedometer error at different speeds.
Visual Comparison
Specification Comparison
| Specification | Difference |
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Speedometer Error
When you change tires, your speedometer may show an inaccurate speed. This table shows the actual speed at different speedometer readings.
Drag the slider — needles show indicated vs actual speed in real time.
| Indicated Speed | Actual Speed | Error |
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Fitment Checker / Clearance
Check if your new tires will fit in wheel wells without rubbing
Fuel Economy Impact
Calculate how larger tires affect fuel consumption
How to Choose Tires for Plus-Sizing
Plus-sizing is the process of installing larger tires on your vehicle to improve performance, appearance, and handling. Before choosing new tires, it's important to understand how the size change will affect your vehicle.
What You Need to Know:
- Larger tires can cause speedometer error - your speedometer will show a lower speed than actual
- Check if there's enough clearance in wheel wells - larger tires may rub when turning
- Larger tire diameter can improve ride and stability, but may reduce acceleration
- Always check manufacturer recommendations for maximum tire size
Complete Guide to Tire Sizes and Replacement
Understanding Tire Size Markings
Tire size markings can look confusing, but each number has a specific meaning. Let's take an example: 225/45R18 95W.
- 225 (Width): Tire width in millimeters, measured from sidewall to sidewall. Wider tires provide better traction but may increase fuel consumption.
- 45 (Aspect Ratio): Sidewall height as a percentage of width. In this case, the sidewall is 45% of 225mm = 101.25mm tall.
- R (Construction): R denotes radial construction, which is standard for modern tires. Older vehicles may use diagonal (D) tires.
- 18 (Rim Diameter): Inner diameter of the tire in inches, which must match your rim diameter.
- 95 (Load Index): Maximum load the tire can support. 95 means 690 kg per tire.
- W (Speed Rating): Maximum safe speed. W = 270 km/h. Always choose a rating that meets or exceeds your vehicle's specifications.
When to Replace Tires: Signs of Wear
Replacing tires at the right time is crucial for safety. Here are the main indicators that it's time for new tires:
1. Tread Depth
Minimum legal depth is 1.6mm in most countries, but experts recommend replacement at 3mm for summer tires and 4mm for winter tires. Use the coin test: place a 1 euro coin in the tread - if the gold rim is fully visible, it's time to replace.
2. Tire Age
Tires over 6 years old should be carefully inspected, and tires older than 10 years should be replaced regardless of tread. Find the DOT code on the sidewall - the last 4 digits show the week and year of manufacture (e.g. 2319 = 23rd week of 2019).
3. Visible Damage
Cracks in rubber, bulges on sidewalls, exposed steel wire, or uneven wear are signs that tires need immediate replacement. Even small bulges can lead to tire blowouts at high speeds.
4. Vibrations and Noise
Unusual vibrations or increased noise during driving may indicate imbalance, misalignment, or internal tire damage. If in doubt, have an expert inspect the tires as soon as possible.
Plus-Sizing Guide: Benefits and Risks
Plus-sizing means increasing rim diameter while maintaining approximately the same overall tire diameter. For example, going from 225/60R16 to 225/45R18 gives a larger rim but lower tire profile.
✅ Plus-Sizing Benefits:
- Better handling: Lower tire profile reduces sidewall flex, providing more precise steering response. Niži profil gume smanjuje savijanje bočnih strana, što daje precizniji odziv upravljača.
- Improved aesthetics: Larger rims fill the wheel arch better and give a sportier look. Veći naplatci pune prostor točka bolje i daju sportskiji izgled.
- Better braking: Wider contact patch and less tire flex can shorten stopping distance on dry pavement. Šira površina kontakta i manje savijanje gume mogu skratiti zaustavnu udaljenost na suhom asfaltu.
- Increased stability: At high speeds, lower profile reduces tire "wobble" and improves stability. Pri visokim brzinama, niži profil smanjuje "ljuljanje" gume i poboljšava stabilnost.
⚠️ Plus-Sizing Downsides:
- Harsher ride: Less rubber means less shock absorption. You'll feel every pothole and road imperfection. Manje gume znači manje apsorpcije udaraca. Osjetit ćete svaku rupu i neravninu ceste.
- Higher costs: Larger rims and tires are significantly more expensive to purchase and replace. Veći naplatci i gume su značajno skuplji za kupnju i zamjenu.
- Risk of damage: With less rubber protecting the rim, there's greater chance of rim damage from potholes or curbs. S manje gume koja štiti naplatak, veća je šansa za oštećenje naplatka od rupa ili rubnjaka.
- Speedometer error: Even small differences in overall diameter can cause inaccurate speed and odometer readings. Čak i male razlike u ukupnom promjeru mogu uzrokovati netočna očitanja brzine i kilometraže.
- Clearance issues: Even if overall diameter is similar, greater width may cause rubbing on fenders when turning or on uneven terrain. Čak i ako je ukupni promjer sličan, veća širina može uzrokovati trljanje o blatobranu pri okretanju ili na neravnom terenu.
Tire Maintenance: Extend Their Lifespan
Proper maintenance can extend tire life by 10,000+ kilometers and improve safety.
Check Pressure Regularly
Check tire pressure monthly and before long trips. Improperly inflated tires (either under or over) cause uneven wear, poor fuel economy, and blowout risk. Use the recommended pressure from vehicle manual (not the maximum pressure on the tire). Check when tires are cold for accurate readings.
Rotate Tires Every 10,000 km
Front and rear tires wear differently. Front tires typically wear faster due to steering and most of the weight on front-wheel drive. Regular rotation (every 10,000-12,000 km) ensures more even wear and extends the life of all tires. Follow the rotation pattern recommended for your vehicle.
Alignment and Balancing
Poor alignment causes rapid and uneven tire wear and can make the vehicle pull to one side. Check alignment annually or if you notice unusual wear. Balance tires at every mounting to prevent vibrations.
Change Driving Habits
Aggressive driving with hard acceleration, heavy braking, and fast cornering accelerates tire wear. Smooth, predictable driving not only saves tires but also fuel. Avoid potholes where possible and don't drive over curbs.
Winter vs Summer Tires: What's the Difference?
Many drivers assume summer tires are sufficient year-round, but the differences are significant:
☀️ Summer Tires
Optimized for temperatures above 7°C, summer tires offer:
- • Harder rubber compound for durability
- • Smaller tread for better dry performance
- • Excellent grip on warm pavement
- • Shorter stopping distance in warm conditions
- • Lower rolling resistance = better fuel economy
⚠️ DANGEROUS below 7°C - rubber becomes hard and loses traction
❄️ Winter Tires
Designed for temperatures below 7°C, winter tires provide:
- • Softer rubber compound that stays flexible in cold
- • Deeper tread with more sipes for snow traction
- • Superior grip on ice, snow, and wet surfaces
- • Up to 50% shorter stopping distance on snow
- • Specialized compound for low temperatures
💡 Legally mandatory in many countries from November to April
🔄 All-Season Tires: The Compromise
All-season tires are a compromise between summer and winter tires. They perform decently in moderate conditions but don't reach the performance of specialized tires. Best for areas with mild winters without much snow. If you live in an area with real winters or hot summers, separate sets will always be the safer option.
Safety Tips for Tire Replacement
- 🔴 Never mix types: Don't combine summer, winter, and all-season tires on the same vehicle.
- 🔴 Replace in pairs: If replacing only 2 tires, put new ones on the rear axle for better stability.
- 🔴 Respect load index: New tires must have equal or greater load index than originals.
- 🔴 Appropriate speed rating: Never go below the manufacturer's recommended speed rating.
- 🔴 Professional installation: Always have a qualified technician mount and balance tires.
Frequently Asked Questions
What is aspect ratio?
Aspect ratio is the percentage of the tire's sidewall height relative to its width. For example, in 275/55R20, 55 means the sidewall height is 55% of the tire width (275mm).
How do larger tires affect fuel economy?
Larger tires usually increase fuel consumption due to greater weight and rolling resistance. However, the difference is usually minimal (1-3%).
Can I install any tire size?
No, you must follow the vehicle manufacturer's recommendations. Oversized tires can cause handling, braking problems, and may damage the vehicle.