I had an idea the other day for a way to measure a car's tire pressure that wouldn't require any action on the part of the driver. Think of it as a remote passive tire gauge. The problem is, I don't know if it would work.
The idea is to put a plate in the ground at gas pumps. The plate would have sensors that measure two things: the weight of the car, and the area of the tires' footprint. Dividing the weight by the area gives pounds per square inch, the inflation of the tires. For more useful information, the plate can be divided in four to measure each tire independently.
Will it work? I know the footprint of the tire increases with weight. Imagine putting a large load on top of your car: it will settle lower, flattening more of the tire against the ground, increasing the footprint at the same time that the weight increases because of the load.
But is the relationship direct enough to make accurate measurement possible? One co-worker argued that low-profile tires are much wider than high-profile tires, and so have larger footprints, even with the same inflation pressure. I think it's possible that the structural support of the tire itself (that is, the rubber) makes the measurement useless. A large portion of the tire's response to the weight of the car is not related to the air in the tire. Imagine a completely flat tire: it doesn't have a footprint large enough for the division to come out to 5psi, for example.
So, is this a useful idea? Does it get us any part of the way to alerting drivers that their tires are low? I think it would be useful to tell people that without them having to check the pressure themselves.
PS: if anyone out there builds this thing and becomes fabulously wealthy, I expect a cut!