Brake & tire questions, answered.

A solid TPMS light usually means at least one tire is low on air. A light that flashes for 60 to 90 seconds at startup and then stays solid usually means a sensor fault or a dead sensor battery, not just low pressure. Check and correct your pressures first; if the light keeps flashing after that, have the sensors scanned at a tire shop.

A steady check engine light usually means you can drive carefully and get it diagnosed soon. A flashing check engine light is different and means stop driving as soon as it is safe: it typically signals an active misfire that can damage the catalytic converter. Pull over, and if it keeps flashing, get the car towed rather than driven.

Most manufacturers consider about 3 mm (roughly 1/8 inch) of friction material the point to replace, and many shops flag pads at 4 mm so you have time to plan. New pads start around 10 to 12 mm. If you are below 3 mm on any pad, or the inner and outer pads differ by more than about 2 mm, have the brakes inspected. This is general guidance, not a substitute for a mechanic measuring your specific pads.

Manufacturers generally recommend changing brake fluid about every two years regardless of mileage, because brake fluid is hygroscopic and absorbs moisture from the air, which lowers its boiling point over time. Always use the DOT rating listed in your owner's manual and never mix types. If your pedal feels soft or the fluid looks dark, have it checked sooner.

A compact donut spare is built for emergencies: most makers say keep it under about 50 mph and under roughly 70 miles, just far enough to reach a tire shop. A full-size spare can go farther but should still be checked and matched to your other tires. Donut spares also need much higher pressure than regular tires, often around 60 PSI, so check it before you rely on it.

The legal minimum in most US states is 2/32 of an inch, but AAA and many safety groups recommend replacing at 4/32 inch because stopping distance on wet roads increases sharply below that. You can check with a tread depth gauge or the quarter test. Replace sooner if you see uneven wear, cords, or sidewall damage, and have a professional look at any sidewall bulge.

The cleanest way is an OBD2 scanner: plug it into the port under the dash, read the code so you know what triggered it, then clear it. A battery disconnect can also reset it, and the light will clear on its own after several good drive cycles once the underlying issue is fixed. Do not simply clear the code to hide a real fault; if it comes back, get it diagnosed.

First set every tire, including the spare on some vehicles, to the PSI on the driver's door jamb sticker. Many cars then clear the light automatically after a short drive. Others need a relearn: a dashboard reset button, a menu option, or a short drive above 15 to 20 mph. If the light returns, you likely have a slow leak or a faulty sensor worth checking at a shop.