4. Routine maintenance, inspection and operational testing of the emergency generator and associated. components must be overseen by a properly trained person [see MSFC(07), Sec. 604.5; NFPA. 99(99), Sec. 3-4.4.1.1(b)3; NFPA 110(99), Sec. 6-4.7; NFPA 110(02), Sec. 8.4.7].
Replace the tires at least every 6 years. If you're not sure, the minimum replacement time that is recommended by the NHTSA is six years regardless of use, with 10 years being the maximum service life for tires. Check your owner's manual for specific recommendations related to your car.s the tires wear, these bars will become flush (level or even) with the tire's tread. At this point, it's time to replace the tires. 3. Check the tread by using the penny test.  Take a penny, and place it upside down with Lincoln facing you in the center of the tread (at the thickest part of the tire).
This allows for inflation, wear and manufacturing tolerances. So you do not need to replace all four tires when you have a flat but you do need to replace the tire with a similar size tire if it cannot be repaired. If all the tires are worn it would make sense to replace the entire set so that they are all matched. have had people tell me that if any one tire is more than 3/32 out that all 4 tires need to be replaced. You mentioned 1/2 inch, that seems like a lot of tolerance, so the tires could be through half of their life and we would only have to replace one tire.