How to Check Tyre Tread Depth: The Norwegian Coin Test
Tyre tread depth directly affects your braking distance, grip, and safety on Norwegian roads. At 3mm depth (versus 8mm new), your wet braking distance can increase by over 40%. Here's how to check your tread and know when it's time to replace.
Norwegian Legal Tread Depth Limits
| Season | Legal Minimum | Safe Replacement Point |
|---|---|---|
| Summer tyres | 1.6 mm | 3 mm |
| Winter tyres | 3.0 mm | 4-5 mm |
| All-season (winter use) | 3.0 mm | 4-5 mm |
🚨 Fines
Driving with insufficient tread depth costs 1,500 kr per tyre — up to 6,000 kr for all four. During EU-kontroll, inadequate tread is an automatic failure.
The Norwegian 2 Kr Coin Test
The quickest way to check your tread depth without any tools:
How It Works
- Take a 2 kr coin
- Insert it into the main groove of your tyre (the deepest channel)
- Look at how much of the coin is hidden:
- Outer ring fully hidden → 3mm+ (legal for winter)
- Outer ring visible → under 3mm (replace for winter use)
Test Multiple Points
Check at least 3 locations around each tyre:
- Center of the tread
- Inner edge
- Outer edge
- Front and back of the tyre (rotate it)
💡 Why Multiple Points?
Uneven wear means one area might pass while another fails. A tyre with 4mm in the center but 2mm on the edge is technically illegal and unsafe.
The 1 Kr Coin Test (Winter Assessment)
For a stricter winter safety check:
- Insert a 1 kr coin into the groove
- If the moose/elk design is partially hidden → 4mm+ (good for winter)
- If the moose is fully visible → under 4mm (consider replacement before winter)
Using a Tread Depth Gauge
For accurate measurements, a digital tread depth gauge costs 100-300 kr and gives readings to 0.1mm precision.
How to Measure
- Place gauge in the main groove (deepest channel)
- Push down until flat against the tread surface
- Read the measurement
- Repeat at 4+ locations per tyre
- The lowest reading is your actual tread depth
Reading Wear Patterns
Wear patterns tell you what's wrong with your tyres or vehicle:
Even Wear (Normal)
- Uniform depth across the tyre width
- Indicates proper inflation and alignment
- Normal — just monitor depth
Center Wear (Over-inflation)
- Center wears faster than edges
- Fix: Reduce pressure to manufacturer specification (check door sticker)
Edge Wear (Under-inflation)
- Both edges wear faster than center
- Fix: Increase pressure, check for slow leaks
One-Side Wear (Alignment)
- Inner or outer edge wears much faster
- Fix: Get professional wheel alignment (typically 800-1,500 kr)
Patchy/Cupping Wear (Suspension)
- Irregular worn patches around the tyre
- Fix: Check suspension components (shocks, bushings)
⚠️ Alignment Issues
One-side wear is very common after hitting potholes or curbs. If you notice uneven wear, get alignment checked immediately — continuing to drive wastes the tyre faster.
When to Replace: Practical Guide
Replace Immediately If:
- Tread below 1.6mm (summer) or 3mm (winter)
- Visible steel belts through the rubber
- Sidewall damage — cuts, bulges, or bubbles
- Tyre age over 10 years (check DOT code)
Plan Replacement If:
- Summer tyres approaching 3mm before next summer
- Winter tyres at 4mm before next winter season
- Tyre age over 6 years
- Uneven wear pattern present (after fixing the cause)
How Tread Depth Affects Performance
| Depth | Condition | Wet Braking (from 80 km/h) |
|---|---|---|
| 8 mm (new) | Optimal | ~38 m |
| 5 mm | Good | ~43 m |
| 3 mm | Adequate (summer min safe) | ~50 m |
| 1.6 mm | Legal minimum | ~58 m+ |
ℹ️ The Difference Is Real
A tyre at the legal minimum (1.6mm) needs over 50% more distance to stop in wet conditions compared to a new tyre. At highway speeds, that's the difference between stopping safely and a collision.
Seasonal Tread Checks
Before Winter (October)
- Measure all winter tyres from storage
- Replace if below 4-5mm for safe winter performance
- Check for age-related cracking from storage
After Winter (April)
- Measure winter tyres before storing
- Note remaining depth to plan for next year
- Inspect for salt and debris damage
Key Takeaways
- Use the 2 kr coin test for a quick 3mm check
- Check multiple points on each tyre for uneven wear
- Replace winter tyres at 4-5mm, not the 3mm legal minimum
- Uneven wear patterns indicate vehicle issues to fix
- A depth gauge (100-300 kr) gives the most accurate reading
Need a professional tread depth assessment? Contact Kisolve for a comprehensive tyre inspection and replacement advice.