Your tires are the only part of your car that actually touches the road. Everything else — brakes, suspension, steering — works through the tires. Which means tire condition affects everything about how your car behaves in a real situation.
Here's what a proper tire inspection covers.
Tread depth
Tread depth is measured in 32nds of an inch. New tires typically start at 10/32 or 11/32. The legal minimum in Illinois is 2/32, but 2/32 is not a safety threshold — it's a legal threshold. At 2/32, your wet-weather traction is significantly compromised. The practical threshold for safe wet driving is 4/32.
A quick way to check: the quarter test. Insert a quarter upside down into a tread groove. If you can see the top of Washington's head, you're at about 4/32 or less. If you can see the top of Lincoln's head on a penny, you're at 2/32 or less.
Wear pattern
Where the tread is wearing tells a story. Even wear across the whole tread width is what you want. Center wear (faster in the middle) indicates chronic overinflation. Edge wear (faster on both sides) indicates chronic underinflation. One-sided wear (on the inside or outside edge only) indicates an alignment or camber issue. Cupping or scalloping along the tread indicates worn or failed shock absorbers.
Sidewall condition
Cracks or bulges in the sidewall are a serious concern. A bulge indicates internal structural damage — usually from a hard impact — and means the tire can fail suddenly. A cracked sidewall on an older tire means the rubber is aging and degrading. Neither condition is safe to drive on.
Valve stems and TPMS sensors
Rubber valve stems crack and dry out over time. A leaking valve stem is a slow tire deflation that TPMS often doesn't catch until you're significantly low. Metal valve stems are more durable. If you have TPMS sensors, they're built into the valve stem on many vehicles and have batteries that last 5–7 years.
What to do with the findings
Tires below 4/32 approaching winter in Illinois should be replaced. Tires with sidewall damage should be replaced regardless of tread depth. Uneven wear patterns should be addressed by fixing the root cause (alignment, inflation, suspension) — replacing tires without fixing the cause means the new tires will wear the same way.
At ProAuto, we check all four tires during every service visit and note anything that warrants attention.
ProAuto | 6100 W Dempster St, Morton Grove, IL 60053 | (847) 232-7777
Serving Morton Grove, Skokie, Niles, Glenview, Northbrook, Evanston, Wilmette, and the North Shore.
