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The pictures above show the fit of race-level electronics and battery pack. Note how close to the centre of the car all the equipment fits. Cooling slots provide as much air as possible to the battery pack.

Aluminium pivot joints are used to adjust and hold hinge pins. aluminium threaded shock bodies, new lower spring perches and aluminium clamp-style wheel hex adapters are standard for a precise fit and feel. aluminium spacers are provided with the Pro 4 kit for adjusting the roll centre and width of the car.


New for HPI is the standard 6-ball bearing steering assembly, providing a slop-free steering setup. New ball cups and socketed ball ends are also included to eliminate steering slop. Ackerman can be easily adjusted by moving the steering links to optional holes on the woven graphite steering plate.


The aluminium spur gear hub spins on ball bearings for maximum efficiency. The motor mounts to a strong aluminium motor mount. The aluminium drive shaft "floats" within carbon graphite drive cups for less rotational mass.


The battery is positioned as close as possible to the shaft, to put the most weight down the centerline of the car. The Pro 4 will be able to fit any standard stick-type or side-by-side battery pack with the included battery rails and strap.


The rear ball differential uses carbide diff balls and bevel gears for maximum efficiency and durability. A front one-way differential will be provided with the car.


In this picture you can clearly see the extremely low centre of gravity (CG) that is provided by the Pro 4 design. Also, the drivetrain sits as low as possible in the car, something not possible with belt drive cars.


The Pro 4 was designed with an all-new shaft drive drivetrain, optimised suspension set up, twin deck C/F chassis and perfected ackerman steering geometry for all types of track layout's and racing conditions. The most noticeable change is to the drive-train which utilises a highly efficient shaft-drive 4wd transmission. Back-to-back track testing revealed the benefits of low maintenance & fast acceleration that a shaft drive transmission offers. The RS4 Pro 4 will be a self-assembly kit form with key items like the radio, ESC, body and tyres left to the choice of the driver. The Pro 4 uses the highest quality materials & will have an amazing specificationto make it a force at the highest level of competition.

Purple Anodised Aluminium Motor Mount & Lightweight Driveshaft

Our HPI Team Drivers will be racing the Pro 4 at all major touring car races as soon as the car is available - ensuring trackside factory support, Team Set-up's and the essential, continued development of the platform to keep the Pro 4 at the top of the winning circle.

Lowest Centre of Gravity in Class

Main Features:

  • Woven Graphite Main Chassis
  • Woven Graphite Upper Deck
  • Woven Graphite Shock Towers
  • Woven Graphite Steering Plate
  • Purple Titanium Turnbuckles
  • MIP CVD's
  • Carbon Plastic: Arms, Uprights, Hub Carriers, Steering Blocks, and Gearboxes
  • Carbide Ball Differential
  • Front One-way
  • aluminium Threaded Shocks with Bladders
  • aluminium Main Drive Shaft
  • aluminium Motor Mount
  • aluminium Spur Gear Adapter
  • aluminium Hex Clamp Hubs w/ adjustable Track (Width)
  • Efficient 64 Pitch Spur and Pinion Gears
  • Socket (Hex) Screws and Fasteners used throughout chassis
  • Pre-cut Urethane Foam Bumper
  • Drive Ratio: 2.4375
  • High Quality Ball Bearings used throughout (24)
Overall Lightweight Chassis for Best Performance

Front Suspension Features:

  • Adjustable Camber - via turnbuckles
  • Adjustable Caster - with included 0, 2, 4, and 6 degree uprights.
  • Adjustable Toe - via turnbuckles
  • Variable Ackerman - via the steering plate
  • Bump Steer - adjustable via shims (washers)
  • Adjustable Roll Centre - via shims under the pivot blocks
  • Vertical Inner Camber Link Adjustment - via mounting location and height with shims/ washers. 2 inboard locations
  • Adjustable Down Stops (Droop) - via round point set screws
  • Shock Mounting Positions - 3 holes on the tower and two holes on the arm.
  • Anti-Dive/ Kick-up - adjusted with washers
  • Anti-Roll Bar

Rear Suspension Features:

  • Adjustable Camber - via Turnbuckles
  • Adjustable Toe - via Pivot Blocks (2.5 and 3.0)
  • Adjustable Roll Centre - via shims under the pivot blocks
  • Vertical Inner Camber Link Adjustment - via mounting location and height with shims/ washers. 2 inboard locations and 2 hub locations
  • Adjustable Down Stops (Droop) - via round point set screws
  • Shock Mounting Positions - optimized for progressive wheel rates with 4 holes on the tower and 3 holes on the arm.
  • Anti-Squat - adjusted with washers
  • Wheelbase Adjustment - via washers
  • Anti-Roll Bar

General Features:

  • Top to bottom mounting of gearbox for precise alignment and mesh of gears
  • Carbon Plastics used to increase rigidity and reduce component weight for better chassis response and tuning
  • Adjustable, variable Ackerman steering geometry to increase steering feel and increase corner speed
  • Completely ball raced steering assembly for smooth steering with reduced play
  • Crank integrated servo saver with adjustable tension
  • Included ride height and droop gauge for accurate suspension adjustment.
  • Pivot Ball Block adjustments to maintain suspension precision and to reduce mis-alignment of the suspension pins.
  • 3mm inboard suspension shafts for strength and 2.5mm outboard shafts for reduced weight and improved wheel clearance
  • Set screws used to retain outboard suspension shafts for easier maintenance
  • Overall lightweight chassis for best performance and adjustable ballast positioning with optional ballast weights.
  • Low centre of gravity and centralized weight for improved cornering power and overall responsiveness.
  • Reduced unsprung weight for increased response and improved control
Ultra Stiff Carbon Fibre Chassis Components

Specification may be subject to change

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