Mountain driving safety RV — air brakes + engine brake + descent procedure

Begin descent prep at the summit BEFORE the steep grade begins. Steps: shift to Tow/Haul mode (every modern pickup + most Class A coaches have it), downshift to D3 or lower (manually), engage exhaust brake (diesel rigs only), reduce speed to 35-45 mph BEFORE the steep section, increase following distance to 10+ seconds.

The mantra: 'descend in the gear you would have climbed in.' If you climbed the same grade in 4th gear, descend in 4th. Engine RPM should match what it was during the climb (typically 2,500-3,500 RPM).

• Engage Tow/Haul mode at summit
• Manually downshift to D3 or lower
• Engage exhaust brake (diesel)
• Reduce speed to 35-45 mph before steep section
• Increase following distance to 10+ seconds

Engine brake: any gear-downshift technique that uses engine compression to slow the vehicle. Available on all vehicles. Engage by downshifting manually.

Exhaust brake: separate device on diesel engines that closes exhaust valves to create back-pressure resistance. Engage via dashboard switch. Common on diesel pickups + Class A coaches.

Jake brake: heavy-duty compression-release engine brake on Class 8 commercial trucks. Not present on most RVs but found on diesel-pusher coaches > 36 ft.

Service brakes (the hydraulic pads) work by friction. Friction generates heat. Sustained downhill use (> 2 mi at > 6% grade) heats brake rotors past their fade threshold (typically 600-700°F). Beyond fade threshold: brake pedal feels normal but brakes do not slow the vehicle effectively.

Brake fade is silent. The driver feels normal pedal pressure but the vehicle accelerates anyway. Recognising fade requires watching speedometer + downshift counter, NOT pedal feel.

Runaway truck ramps are state-DOT-maintained emergency stops on mountain highways. Two types: gravity arrestor (uphill sand-bed) + drag arrestor (level deep gravel).

Use criteria: if brakes feel ineffective + speedometer climbing > 5 mph above intended speed + downshift no longer holding speed = RAMP NOW. Hesitation kills. Better to ramp + suffer $5,000-15,000 tow recovery than continue + risk catastrophic failure.

Common ramp locations (verify per state-DOT map): I-70 west of Denver (multiple), I-90 Snoqualmie Pass WA, US-6 Loveland Pass CO (4+ ramps), I-15 north of Las Vegas, US-50 Carson Pass CA.

Service brake use during descent: feather lightly + intermittently. Apply brakes for 3-5 seconds to reduce speed from 45 to 35 mph, then release for 15-20 seconds to allow rotor cooling. Repeat.

Continuous pedal pressure (riding the brakes) is the leading cause of brake fade. Even light continuous pressure generates fade-threshold heat within 2-3 miles.

The under-shared truth: rental fleet rigs often have brakes near service interval (worn pads, glazed rotors). The brake-fade threshold is LOWER on worn brakes. Treat any rental rig's brakes as compromised vs personal-vehicle brakes. Engage engine brake earlier + harder than you would in your own vehicle.

Second under-shared truth: most rental Tow/Haul + exhaust-brake controls are NOT covered in the standard 15-minute walk-through. Specifically request demonstration. The 10 minutes added to walk-through is the highest-leverage safety investment in the entire trip.