How do automobile “tire inflation” indicators work?

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How do automobile “tire inflation” indicators work?

In: Technology
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Are you talking about the sensors that tell you which tire is flat?

They’re just small pressure sensors that transmit wirelessly to the car. When the sensor reads too low, the car will sound the alarm.

There are two main styles

The expensive version is a sensor in the tire that actually measures the pressure in the tire, this one has already been covered. It adds $50-100 per sensor whenever you have to change them which makes new tires wayyyy more expensive

The cheaper version only tells you if one tire is different from the rest. When all your tires are properly inflated they’re all the same diameter so when driving in a straight line they all spin at the same rate. If one of your tires is under inflated then it will be slightly smaller than the rest and spin slightly faster because it has to make up the distance with its smaller circumference. Similarly an over inflated tire is slightly larger and spins slightly slower.

By measuring the rotation rate of all the wheels over a long distance (usually 10-20 miles) your car can tell if one is different from the rest and will throw up a low pressure warning but won’t tell you how low the pressure is because it doesn’t know this.

This seems pretty complicated and requires wheel speed sensors, but those are actually free because they come with your ABS (AntiLock Brake System) and are used to detect if a wheel locks up so taking that input and using it to determine if a tire has gone flat is free.

The downside to this system is that it can’t detect if all your tires are running at a low pressure because you fill them when it was 80 and its now 8, and it can also get tripped up if a single tire is over inflated relative to the rest of the group.