Tyre Sizes Explained: What Do the Numbers Mean?
Those numbers on your tyre sidewall — like 225/60R16 98H — aren't random codes. They tell you exactly what size tyre fits your car, how much weight it can carry, and how fast it's rated to go. Here's how to read them.
Breaking Down 225/60R16 98H
Let's decode each part of a typical tyre size:
225 — Tyre Width (mm)
The width in millimetres from sidewall to sidewall.
- 225mm = approximately 8.9 inches wide
- Common widths range from 155mm (small cars) to 315mm (sports cars)
- Wider tyres generally provide more grip but increase fuel consumption
60 — Aspect Ratio (%)
The sidewall height as a percentage of the width.
- 60 means the sidewall is 60% of 225mm = 135mm tall
- Lower numbers (40-50) = short sidewalls, sportier handling
- Higher numbers (60-75) = taller sidewalls, more comfortable ride
R — Construction Type
- R = Radial (almost all modern tyres)
- D = Diagonal (rare, older vehicles)
- B = Bias-belted (very rare)
16 — Rim Diameter (inches)
The wheel size the tyre fits.
- Must match your rim exactly
- Common sizes: 15", 16", 17", 18", 19", 20"
- Larger rims generally mean lower aspect ratio tyres
98 — Load Index
The maximum weight per tyre.
- 98 = 750 kg per tyre (3,000 kg for all four)
- Never use a lower load index than your vehicle specifies
- Check your door sticker for the required minimum
H — Speed Rating
The maximum safe speed for the tyre.
| Rating | Max Speed |
|---|---|
| T | 190 km/h |
| H | 210 km/h |
| V | 240 km/h |
| W | 270 km/h |
| Y | 300 km/h |
⚠️ Match or Exceed
Always use tyres with a speed rating equal to or higher than your vehicle's original specification. Using a lower rating is unsafe and may be illegal.
How to Find Your Correct Tyre Size
- Door frame sticker — on the driver's side door jamb
- Owner's manual — in the vehicle specifications section
- Current tyres — read the sidewall of your existing tyres
- Registration documents — listed in vehicle specifications
💡 Quick Check
If you're unsure, take a photo of your current tyre sidewall and the door frame sticker. Any tyre shop can match the correct size from these.
Common Norwegian Car Tyre Sizes
| Vehicle Type | Typical Sizes |
|---|---|
| Small cars (Polo, Yaris) | 185/65R15, 195/55R16 |
| Medium cars (Golf, Corolla) | 205/55R16, 225/45R17 |
| SUVs (RAV4, Tiguan) | 225/65R17, 235/55R18 |
| Large SUVs (XC90, Q7) | 255/50R19, 275/45R20 |
| Vans/Commercial | 215/65R16C, 225/70R15C |
Can You Change Tyre Size?
What You Can Change
- Width: typically ±10-20mm from original
- Aspect ratio: adjusted to maintain similar overall diameter
- Rim size: ±1-2 inches (with matching aspect ratio change)
The 3% Rule
The overall rolling diameter should stay within 3% of the original. Larger deviations affect:
- Speedometer accuracy (reads too fast or slow)
- ABS and traction control calibration
- Fuel consumption
- EU-kontroll compliance
ℹ️ Example
Going from 205/55R16 to 225/45R17 changes the rim size but keeps a similar overall diameter — this is a valid upgrade.
What You Cannot Change
- Load index must meet or exceed original specification
- Speed rating must meet or exceed original specification
- Tyre must physically fit without rubbing
Winter vs Summer Tyre Sizes
In Norway, many drivers use:
- Same size for summer and winter tyres (most common)
- Slightly narrower winter tyres (e.g., 205 instead of 225) — can cut through snow better
- Smaller rims for winter (e.g., 16" winter on a car with 18" summer) — cheaper winter tyres and less pothole risk
💡 Winter Size Strategy
Using smaller rims for winter tyres (like 16" instead of 18") typically means taller sidewalls and cheaper tyres. The extra sidewall cushion also helps protect rims from winter potholes.
Understanding the DOT Code (Tyre Age)
On the sidewall you'll also find a DOT code ending in 4 digits, like DOT ... 2423.
- Last 4 digits = manufacturing week and year
- 2423 = week 24 of 2023
- Replace tyres older than 6-8 years regardless of tread depth
- Maximum safe age: 10 years
Key Takeaways
- Width, aspect ratio, construction, rim size — these four define the physical tyre size
- Load index and speed rating — these define the tyre's performance limits
- Never go below your vehicle's specified load or speed ratings
- Stay within 3% of original diameter when changing sizes
- Check the DOT code — old tyres are dangerous even with good tread
Not sure which size is right for your car? Contact Kisolve — we'll match the perfect tyres to your vehicle specifications.