When do tires actually need replacing?

You do not need any tools for three of these, and the fourth needs a quarter.

1. Tread depth

New tires start around 10/32 of an inch. The legal minimum in Michigan is 2/32, but a tire is genuinely compromised in the wet well before that. Wet braking distance climbs sharply below about 4/32.

The quarter test: put a quarter into the tread groove with Washington's head upside down and facing you. If the top of his head is visible, you are at or below 4/32 and should be planning replacement. The older penny test only tells you when you have reached the legal minimum, which is later than you want to find out.

Check in several places across the tread and around the tire, not just one spot.

2. The wear bars

Every tire has small raised bars sitting in the bottom of the grooves. When the tread wears down level with them, the tire is at 2/32 and legally finished. If you can see a smooth band running across the tread, that is the wear bar and the tire needed replacing a while ago.

3. Age

Rubber hardens and cracks with time regardless of mileage. A tire with plenty of tread can still be unsafe if it is old, which catches people out on low mileage cars, spare tires and trailers.

Find the DOT code on the sidewall. The last four digits are the week and year it was made: 3823 means the 38th week of 2023. Most manufacturers say six years, and ten years is an absolute limit. If you see fine cracks in the sidewall or between the tread blocks, it is done.

4. Uneven wear

How a tire wears tells you what else is wrong:

• Both edges worn, middle fine. Chronically underinflated.
• Middle worn, edges fine. Overinflated.
• One edge only. Alignment, usually camber.
• Patchy or scalloped. Worn suspension, or the tire has not been balanced or rotated.

Fixing the tire without fixing the cause just means doing it again next year.

Replace in pairs at minimum

Always replace at least both tires on the same axle so the grip matches side to side. On an all wheel drive vehicle, check the manufacturer's guidance: many require all four, because mismatched rolling diameters can damage the differential. That is an expensive mistake to make to save the cost of one tire.

If you have measured and you know what you need, search your size and we will bring them to your house. If you are not sure, send us a photo of the sidewall and we will tell you what we see.