Forward-wheel drive (FWD), rear-wheel drive (RWD), all-wheel drive (AWD), and four-wheel drive (4WD) systems provide unique benefits in specific rallying conditions.
Rally cars are increasingly heading towards adopting the newer, more advantageous four-wheel drivetrain. But because of the high expense, the other drivetrain systems still have their place outside the world stage.
Quick Info: The Difference Between FWD, RWD, AWD, and 4WD
All four drivetrains are distinct systems, each one handy for contrasting driving needs, began developing at different times in the drivetrain technology evolution.
The FWD and RWD systems are self-explanatory, but the AWD and 4WD have subtle differences and have gotten more sophisticated, blurring the distinction between them – manufacturers using these terms interchangeably didn’t help clear the confusion.
Simply put:
- Forward-wheel drive (FWD): Typically has a transversely front-mounted engine and transmission. They direct power to the front wheels, so the front wheels steer and pull the car.
- Rear-wheel drive (RWD): The engine delivers power to the rear wheels, pushing the car forward while the front wheels steer.
- All-wheel drive (AWD): Can be part-time or full-time AWD. The drivetrain system automatically sends and varies torque to all four wheels to optimize the car’s traction; no manual driver input in this regard. The front and rear axles drive at all times in a full-time AWD; either the front or rear wheels in a part-time AWD, with electronic sensors engaging the other two wheels when road conditions demand extra traction.
- Four-wheel drive (4WD): Can be part-time or full-time (permanent) 4WD. Newer 4WDs have low and high ranges – low for maximum traction in off-road environments; high for slippery on-road conditions such as ice, loose sand, or gravel. Full-time 4WD operates all four wheels continuously. Part-time 4WD typically drives the rear wheels, and the driver can manually engage 4WD when needed. Generally, serious off-roaders opt for the 4WD over the AWD.
World Rally Categories and Drivetrain Systems
Over the last couple of decades, the world rally scene has progressed massively to arrive at its current technical regulations, reflecting the technological advancements in rally car design.
The FIA World Rally Championship officially switches to a four-wheel-drive series across its main and support categories, marking a complete 4WD adoption beginning with the 2022 championship.
These are the categories within the FIA WRC and the drivetrain/tech spec they use:
- World Rally Championship (WRC): Permanent 4WD, 6-speed sequential gearbox with paddle-shift on steering. Plus, 1.6-liter turbocharged 4-cylinder engine (380 bhp max).
- World Rally Championship-2 (WRC2): Permanent 4WD, 5-speed sequential gearbox with paddle-shift on steering. Plus, 1.6-liter turbocharged 4-cylinder engine (285 bhp).
- World Rally Championship-3 (WRC3): Same transmission, gearbox, and engine spec as WRC2, but WRC3 is solely for privateer drivers.
- Junior WRC: FWD cars ended with the 2021 championship. 4WD via a 5-speed sequential gearbox beginning 2022. Plus, 1.5-liter engine that delivers 215 bhp.
New road-going cars are similarly witnessing a widespread adoption of the AWD and 4WD drivetrains as market demands increase and costs decrease.
Why Are Most Rally Cars in National and Grassroots Championships FWD?
For some years now, the World Rally Championships have not seen 2-wheel drive cars (FWD and RWD) in competition.
4WD is the dominant drivetrain rally cars use for the grip and car control advantages on challenging and varying surfaces – tarmac (asphalt), gravel, and snow – and inclement weather.
However, FWD rally cars still have their place in national and amateur competitions.
FWDs are the ideal rally car for beginners due to their simpler powertrain setup, fewer components (therefore cheaper), relatively inexpensive maintenance, and higher gas mileage.
It is the perfect platform to learn the fundamental dynamics of a rally car before transitioning to an AWD.
4WD drivetrains are costlier than 2WD systems mainly because:
- A full-time 4WD requires three differentials – one between the front wheels, another between the back wheels, and the third between the front and rear axles. The differentials transmit engine power to the wheels and allow the driven wheels to rotate at different speeds, thereby playing a crucial role in distributing torque evenly (where needed) and limiting wheelspins. Self-locking differentials further add performance and costs.
- An FWD or RWD has only one differential – between the driven wheels.
RWD cars were the pioneering type in rallying and are still used, mostly at grassroots levels.
But how do FWD and RWD rally cars compare?
FWD & RWD: The Benefits of One Over the Other
A front-wheel-drive rally car is a better rally car than a rear-wheel-drive one overall:
- FWD gives the driver more steering control – the two wheels that pull the car also steer, so it won’t break traction like an RWD.
- FWD edges the RWD in mid and high-speed corners – the front-biased weight percentage provides a more planted feel as the car puts the power to the ground. The RWD has a slightly higher tendency to oversteer.
- FWD is more stable when driving downhill and braking in a straight line – FWDs have the engine and gearbox at the front, so the extra weight at the wheels that steer inspires confidence in handling.
- FWD is cheaper to own and maintain – relatively straightforward components make an FWD cheaper and easier to maintain. The affordability factor lowers the entry barrier for beginners.
- RWD provides more initial traction when accelerating from a standstill – more weight transfers to and concentrates at the rear end as the car pushes forward.
- RWD has the advantage over FWD on tarmac (asphalt) and uphill slopes – rear bias weight distribution adds vertical load to the back tires and generates more grip for accelerations.
- RWD edges the FWD in tighter and slower corners – it’s easier to oversteer with an RWD to assist turning. FWDs tend to understeer.
However, the feel factor matters significantly to a rally driver, so a well-prepared FWD or RWD car can be fast in the hands of the right pilot.
Why Do 4WD Cars Dominate the World Rally Scene?
World Rally Cars are full-time (or permanent) four-wheel drive machines built to maximize traction that the near-400 brake horsepower the turbocharged engines can produce.
The advantage of full-time 4WD for rally cars is straightforward: powering four wheels distributes the engine torque, minimizes wheelspin, and allows higher handling precision.
All FIA-governed regional rally championships are heading in the same 4WD direction as the various categories continue to switch away from 2WD cars.
The Advantages of 4WD in Rally
The four-wheel-drive system provides the most benefits, and in some ways, combine the advantages of the FWD and RWD drivetrains:
- Provides the highest amount of traction – compared to FWD or RWD, especially on rugged terrain and wet conditions.
- Sharper handling – the permanent 4WD sends power to all four wheels and adjusts the torque where needed, which means improved road holding characteristics for the car.
- Stronger acceleration on traction-limited conditions – an RWD may have an edge when accelerating on a clean and dry tarmac (asphalt). Still, rally stages consist of more sand, gravel, and snow surfaces than tarmac.
- Capable of understeering and oversteering – a skilled rally driver takes advantage of these characteristics to maximize the car’s cornering performance.
