How to Tell if Your Winter Tires Will Last One More Season

The 4mm Rule: When Winter Tires Must Be Replaced

Winter tires should be replaced when tread depth reaches 4mm. This is different from all-season tires, which are replaced at 2mm. Winter tires need extra depth for snow and ice grip. At 4mm tread depth, winter tires lose significant grip in snow. Below 4mm, they approach all-season tire performance and become unsafe for winter conditions. Check your tires before each winter season. If tread is below 4mm, replace them. Don't gamble with safety.

Understanding Tread Depth Measurement

Tread depth is measured in millimeters from the top of the rubber to the deepest part of the groove. New winter tires typically have 8-10mm depth. At 6mm, tires are still safe but aging. At 5mm, tires are approaching the replacement threshold. At 4mm, replacement is necessary. At 2mm or below, tires are dangerous in winter. Measure multiple locations across the tire to check for uneven wear. Uneven wear indicates alignment or suspension problems. Address these issues before buying new tires.

Winter Tire Tread Depth Guide

• 10mm: New winter tires, optimal grip
• 8mm: Excellent performance, safe
• 6mm: Good performance, still safe
• 5mm: Acceptable but aging, monitor closely
• 4mm: Replacement threshold for winter tires
• 3mm: Dangerous in winter, must replace
• 2mm: Legal minimum for all-season, unsafe for winter
• Below 2mm: Dangerously worn, immediate replacement

The Penny Test: Quick Tread Depth Check

The penny test is a simple way to estimate tread depth. Take a penny and insert it upside down into the tire's tread groove. If you can see the top of Lincoln's head above the tread, tread depth is approximately 2mm or less. Tires need replacement. If the tread covers part of Lincoln's head, depth is somewhere between 2mm and 4mm. If tread completely covers Lincoln's head, depth is above 4mm. The penny test is not precise but gives a quick indication. Use a tread depth gauge for accurate measurement.

Tread Depth Gauge: The Accurate Method

A tread depth gauge is a small tool that measures tread depth precisely. Insert the gauge into the tire's deepest groove and note the reading. Measure at multiple locations: center, inner edge, and outer edge. Uneven readings indicate alignment or suspension issues. Gauges cost $5-$15 and are worth the investment. Most tire shops will measure for free. Many shops include tread depth measurement during routine maintenance. Ask your mechanic to check depth every season.

Wear Patterns: What Uneven Wear Tells You

Winter tires should wear evenly across the width. Center wear indicates overinflation. Edge wear indicates underinflation. One-sided wear indicates alignment problems. Scalloped wear (wavy pattern) indicates suspension problems. Uneven wear reduces grip and shortens tire life. If you notice uneven wear, have your vehicle's alignment and suspension checked. Fixing these issues will improve tire life and safety. Don't just replace tires. Address the underlying problem.

What Wear Patterns Mean

• Center wear: Overinflated tires, reduce pressure
• Edge wear: Underinflated tires, increase pressure
• One-sided wear: Alignment issue, get alignment checked
• Scalloped wear: Suspension problem, get suspension inspected
• Uneven wear: Multiple issues possible, see a mechanic
• Even wear: Proper inflation and alignment, tires are fine
• Wear on one tire only: Braking issue, check brakes

Winter Tire Age: When Tires Get Too Old

Winter tires have a lifespan beyond tread depth. Even if tread depth is above 4mm, tires older than six years should be replaced. Rubber compounds degrade over time. UV exposure, temperature changes, and oxidation weaken tires. Check the tire's manufacturing date on the sidewall: a four-digit code showing the week and year of manufacture. If tires are older than six years, replace them regardless of tread depth. Safety is the priority.

Seasonal Inspection: Your Pre-Winter Checklist

Before each winter season, inspect your winter tires. Check tread depth using a gauge or penny test. Look for sidewall damage, cracks, or bulges. Verify tire pressure is correct (cold temperature reduces pressure). Check for uneven wear patterns. Rotate tires if you've driven on them during off-season. Ask your mechanic for a formal inspection if you're unsure. A small investment in inspection prevents larger problems. Safety starts with proper tire maintenance.

Frequently Asked Questions