You fire up the car, coffee in hand, and then that light stops you right in your tracks. Nothing puts a dent in the morning routine and commute quite like a TPMS warning.
As it should – Tire Pressure Monitoring Systems (TPMS) are not commonly faulty, and so if low tire pressure is being signaled, it’s likely that one or more of your tires have slipped into a hazardously low pressure status. You shouldn’t drive until all four wheels and tires have been thoroughly evaluated.
So how does a layperson conduct a check of tires for low pressure, identify the cause of pressure loss, and evaluate road-worthiness? Here’s some guidance.
If your TPMS doesn’t display individual tire pressure but rather signals only for a loss of pressure on one or more wheels, then a visual inspection of all four tires in search of the affected tire is a reasonable first step.
You’re looking for a clearly flat tire or a comparatively compressed and bulging tire sidewall that is characteristic of a tire with low pressure. Also, listen for any “hissing” noise as you inspect the tires.
Note that, unfortunately, low tire pressure is not always visually distinct. Even a substantial 10-20 psi difference between tires won’t necessarily be visible in terms of how the lower pressure tire is interacting with the road surface the stationary vehicle, so apparent consistency between the look of all four tires doesn’t mean “all clear.”
If your visual check unveils no real clues about which tire(s) are low, then the next step is a tire pressure check of all four tires. Tire pressure measuring devices are available at any auto parts store, large retailers, gas stations, and tire shops. (Pressure devices are inexpensive or even complimentary at many tire shops.)
With a tire pressure measuring device, check all four tires and note the pressures. How do they compare to one another? Are there any tires that are measuring low by comparison? How far off are any of the tires from vehicle specification? (For more details and in-depth instructions see Knowing your tire pressure and How to do a quick tire safety check.)
Along with clear signs of tire pressure loss, look for possible structural issues like sidewall bubbles, extreme low tread, bead damage (where the tire meets the wheel edge), or other abnormalities. If any of these issues are present, in combination with a loss of pressure, then the tire is potentially compromised and shouldn’t be driven on. Even the re-inflation of a tire in such condition can be very dangerous and shouldn’t be attempted.
If you’ve identified the tire with low pressure, a focused review of that tire could pinpoint the cause.
As detailed above, a soapy water solution coated at the tire-wheel sealing point will create bubbles if air is leaking. Remember that for a thorough check, both inner and outer tire-wheel sealing points would need to be checked, which requires the safe removal of the wheel.
What about the “curious” case of all four tires being low pressure? Has a thief in the night absconded with your tire pressures?
Well, probably not. The likeliest cause of a consistent pressure loss affecting all four tires is a drop in temperature. When temperatures drop, and air condenses, there is a predictable corresponding loss of tire pressure.
If tire pressure loss has resulted from a drop in temperatures, then take it easy and drive at reduced speeds. Re-inflate your tires to vehicle specification at first opportunity.
You should only investigate a loss of tire pressure to the extent that you are comfortable and able. For example, if you lack the know-how to jack up your vehicle and remove a wheel for a comprehensive tire review, then get a professional to do it.
Other safety principles to keep in mind:
Overall, the best thing you can do for your tires is to check your tire pressure every month. This will help your tires reach their optimal traction, stability, and durability. Just like a balloon that starts to lose air after a few days, tire pressure changes over time. Even though tires are fairly airtight, there are still microscopic pores in the tire walls that let very small amounts of air escape over time.