18 Off-Road Driving Flashcards
First step in safe off-road driving:
A thorough knowledge of the vehicle
Drivers must understand the vehicles:
capabilities and (more importantly) limitations
Front Wheel Drive Advantages
- Provide better traction on slick roads - weight of engine, transmission, and mechanical components rest on front axle
- Most provide better fuel economy
Front Wheel Drive Disadvantages
- Tends. to be nose heavy
- Susceptible to Torque Steering (may pull to right or left during heavy acceleration)
Rear Wheel Drive Advantages
- Better acceleration
- Better weight distribution - improves stability and handling.
Rear Wheel Drive Disadvantages
- Poor handling on slick roads
All Wheel Drive
Designed to handle slippery conditions on a paved highway.
Four Wheel Drive
Power transfers from drive train to transfer case where power is divided front and rear axles so maximum torque is applied to all four wheels
4WD Low
- Designed to provide more torque for off-road use
- Slow speeds
- More power to go up hills and increased engine braking to descend hills
- Does not provide more traction, just torque
Crawl Ratio
Ability to travel over rough terrain in first gear at idle speed without having to depress the clutch pedal to keep the vehicle from stalling
4WD High
- Designed for slippery conditions like loose dirt, gravel, or sand
- Not designed for rough off-road conditions
Open DIfferential
Torque is split equally between wheels on the axle
Locking Differential
Wheels on the axle are locked together and will both spin at the same speed when torque is applied - regardless of traction.
Limited-Slip Differential
Combine advantages of Open and Locking - Allows tires to rotate at different speeds but also allow torque transfer between tires when needed.
Off Road Driving Considerations
- Driving Surface
- Terrain
- Vehicle
Off Road Operations
- Drive straight up or straight down hills
- Driving across a cross-slope or down a hill may cause a rollover
- If vehicle begins to slid on a cross-slope, turn the wheels in the direction of slid and let off pedals
- Angle of approach and angle of departure may cause it to get stuck as the vehicle tries to go up or down a hill
More Off Road Ops
- Know the hill-climbing limitations of vehicle
- Understand that the slope of the hill may be too severe for parking brake to hold
- Always use chocks when the vehicle is parked
- When climbing a hill, weight shifts to back causing vehicle to sink onto the rear suspension
Even more off road ops
- When climbing a hill, know what is on the other side
- If vehicle stalls, back down the hill and try again
- Depressing clutch when on a hill may cause the vehicle to roll backward
- When going downhill, use lowest gear possible and allow engine compression to brake the vehicle.
Still more off road ops… get used to it.
- Spinning wheels while stuck may cause vehicle to dig in and sink further
- When climbing or mounting obstacles, use low gear at idle speeds
- Don’t straddle rocks, stumps, or other ground obsttructions. Drive over them instead
- If you must straddle, use a spotter and ensure that the vehicle does not strike the obstacle with any part of the undercarriage.
You want more off road ops!
- Know layout of undercarriage and where lowest points are located
- When crossing a ditch, know angle of approach and departure
- Beware of rocks that may become wedged in dual rear tires
- Be very aware of the capabilities of the road
Crossing water/mud off-road ops, the same but different.
- Check depth BEFORE driving in it
- After crossing, braking efficiency may be reduced due to wet brake components
- Know where the air intake on the vehicle is located - don’t let water into the engine
- Drive slowly. Can’t see what is in front of vehicle
Off road ops, driving in sand… Last one, I promise.
- Keep moving at all times so as to not get bogged down.
- Reducing tire pressure will help balloon the tires, increasing the surface area that is in contact with the gorund
- If tire pressure is reduced, higher chance of tire bead separating from rim, resulting in a flat tire.
- If vehicle gets stuck, wet the sand to increase traction
- Don’t spin the tires
- If possible, roll to a stop - brakes may cause vehicle to skid or dig into the sand
- If deflating tires for off-road driving, re-inflate them immediately upon returning to the pavement.
