[post updated 6/12/2017]
Tire Pressure Monitoring System (TPMS)
Weather you know it or not, your original factory Jeep JK comes with a Tire Pressure Monitoring System (or TPMS for short). The purpose of TPMS is to monitor your tire pressure and warn you if any one of your tires is significantly under-inflated and possibly causing an unsafe situation.
This device is actually a small electronic tire pressure gauge with a low powered radio that transmits its reading to the vehicle’s computer. The TPMS indicator is a yellow symbol that illuminates on the dashboard instrument panel of your Jeep and looks like the cross-section of your tire with an exclamation point.
Before this indicator light, knowing whether your air pressure was low using a tire gauge, or “eye balling” how much your tires bowed where they rest on the ground. This is especially difficult on large off road tires, and even more difficult with tires that are aired-down.
When replacing your wheels you’ll need to make a decision about the TPMS sensors that would be included on your factory wheels. These sensors typically last for 7 to 10 years. If you’re reusing your factory wheels you can just leave them in place. If you’re buying new wheels you have the option to (a) move them to the new wheels, (b) buy new ones (for about $45 a piece, and the spare has one too), of (c) eliminate them and just in stall regular valve stems.
I always ensure that the TPMS is operating when I upgrade a vehicle. I know that most vehicles will be driven on the highway / at high speeds, and I never know who might end-up driving the vehicle. Additionally, if you just replace the TPMS sensors with valve steps you will be faced with the annoying low pressure dash indicator.
The one down side of maintaining the TPMS is that some Jeep owners will choose to run their tires slightly under inflated (because it improves ride quality, offsetting the more firm ride that comes for higher load rated truck tires; or because they’re running a wheel that is on the narrow side and know that achieving even tire wear across the tread will require a little less air pressure)