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].
If rain and wet roads are a concern, you should consider replacing your tires when they reach approximately 4/32 of remaining tread depth. Since water can't be compressed, you need enough tread depth to allow it to escape through the tire's grooves.f two of your tires have a lot of remaining tread depth, but you need to replace the other two because they were damaged or have worn out, you should replace them with a pair of tires that come as close as possible to matching your existing tires.
This means fitting the right tyres and for safety ensuring that they are inflated to the manufacturer's recommended pressure. The legal limit for minimum depth of the tread on your tyres is 1.6 millimetres, across the central  of the tread around the complete circumference of the tyre. For safety reasons it is recommended that you replace your tyres before the legal limit is reached. Many vehicle manufacturers recommend replacing at 3 millimetres. At 1.6 millimetres in wet weather it takes an extra two car lengths (8 metres) to stop at 50 mph than if your tread was 3 millimetres. A regular check of your tyres can help you to avoid 3 penalty points and 2,500 in fines for having tyres worn beyond the legal minimum limit on your vehicle.