Parking a Loaded Rig on an 8% Gravel Pullout
You are parked for the night at a gravel pullout on NM-518 south of Taos. The truck is a 2017 Peterbilt 579 with a 53-foot flatbed loaded with lumber, 68,000 lb GCW, facing downhill toward the two-lane highway. The pullout is gravel and slopes about 8%. There are no wheel chocks within 100 feet. The temperature is 18°F and the air tanks have not been drained since morning. You set the parking brake and release the service brake; the rig creeps forward about 6 inches before stopping. You need to leave it parked while you check in at a motel 200 yards away. The tractor has a yellow dash valve for the spring brakes and a trailer spring brake valve. You have a CB and a phone.
1. Is the 6-inch creep acceptable? What does it indicate about the spring brakes or the parking situation?
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Six inches of creep on an 8% grade is not acceptable. Spring brakes should hold a parked vehicle on the grade it is parked on; movement means the holding force is marginal. Possible causes include spring brake chambers that are out of adjustment, a leaking or contaminated spring brake valve, oil on the linings, or a grade steeper than the brakes can hold. I would not walk away and assume it will stay. The creep also means the rig is relying on friction that may change as the gravel shifts or the brakes cool. Before leaving, I would try to reposition the rig to a level spot or a gentler slope. If that is impossible, I would set the spring brakes, turn the front wheels toward the ditch or curb, place chocks if any can be found, and release the service brake so the spring brakes and chocks carry the load.
2. What parking procedure should you use, and what would you do if no chocks can be found? What should you check before the next trip?
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The safe procedure is to stop, set the spring brakes, turn the front wheels toward the ditch or curb, place chocks at the wheels, release the service brake, and let the rig settle against the chocks and spring brakes. Then shut the engine off. In 18°F weather I would also drain the air tanks after parking to reduce the chance of frozen moisture. With no chocks within 100 feet and an 8% slope, the better choice is to move the truck to a safer location rather than trust a marginal park. If I had to stay, I would use the CB or phone to arrange help or find chocks, and I would not leave the rig unattended. Before the next trip I would check pushrod travel on the spring chambers, test the parking brake hold, and inspect for oil or grease on the linings.