Cold-start air pressure and a sidewall cut
It is 05:40 in January, outside Tetovo, with the temperature at -3 °C. You are due to drive a 3-axle rigid truck with air brakes. During the daily check, the engine has been running for four minutes and the dashboard air gauge shows 6.8 bar; the low-pressure warning buzzer is still sounding and the maximum governed pressure is 8.0 bar. The front right tyre has a cut in the sidewall about 3 cm long and 1 cm deep; the tread depth is 5 mm. The other tyres look serviceable. The parking brake holds the truck on a slight slope. The tachograph is working and the load is already secured. You have a 07:00 delivery 90 km away. You must decide whether to depart, what to test before moving, and what to do about the tyre.
1. Is the air pressure reading acceptable for departure, and what tests should you perform?
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No. With the engine running, the gauge should reach the system's normal operating pressure, typically around 8 bar or the manufacturer's specified cut-out, and the low-pressure warning should stop. At 6.8 bar the buzzer is still warning, so the system is not ready.
Before moving, build pressure until the compressor cuts out, then stop the engine and listen for leaks; observe the gauge for a pressure drop over a few minutes. Check that the parking brake and service brake hold, and drain any moisture from the air tanks if the vehicle has manual drains. In cold weather, moisture can freeze in lines or valves. Do not 'drive it off' to warm up the system. If pressure will not build or falls noticeably, the vehicle must be left parked and reported.
2. What do you do about the front right tyre and the delivery deadline?
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The cut is on the front right sidewall, which is a steering tyre and highly safety-critical. A 1 cm deep sidewall cut may expose or weaken the cord; even if it does not, sidewall damage cannot be judged safe from outside alone. The 5 mm tread may be above the minimum, but that does not compensate for sidewall damage. Do not depart on that wheel.
Replace it with a serviceable spare or call for tyre service; then re-check wheel nuts and pressure. The 07:00 deadline does not justify risking a front tyre blowout with a loaded truck. Notify the dispatcher, record the delay, and if you cannot replace the tyre safely, do not move the vehicle. The correct decision is to make the vehicle roadworthy first, then plan the route and any tachograph implications.