Not a Hot Rod thing, but I learned something today, and while I understand the concept it really surprised me to learn of a second type of tire pressure monitoring being used on OEM vehicles. I'll admit being surprised when the individual tire pressure transmitters were introduced, one in each wheel often as a part of the valve stem. Today I learned that there are some that use the ABS system to determine low pressure in a tire. The ABS watches for differential tire speed, and in braking reduces pressure to any tire that is slower than the others by a set margin, preventing lock up of a wheel or wheels. The same monitoring is being used to detect low pressure in a tire by detecting a tire that's going slightly slower when NOT in severe braking. The lower pressure reduces the OD of the tire slightly, triggering the light. My oldest son has a gas sipping Honda Accord Sport, 1.5L turbo four with a six speed, and the ABS low tire pressure trigger.

Am I the only one who didn't know about using differential wheel speed to indicate pressure differences?