As a long-time enthusiast of Group C racing and particularly drawn to the iconic Mercedes-Benz, Nissan, and Jaguar body styles, owning a model that captures this era has always been a desire. Recently, I acquired the re-released Mercedes-Benz C11 1990 Group C, finally bringing this dream to reality. While the allure of the silver livery is undeniable, I opted for a personal touch and painted mine in a vibrant red, setting it apart from the standard.
The C11 chassis presents an intriguing blend of design philosophies, incorporating a bathtub-style mid-section with pan car elements. This fusion is appealing, yet it also reveals limitations, notably in the adjustability of the car’s setup and the asymmetrical steering design at the front. To unlock the full potential of this classic model and enhance its performance, I embarked on a chassis upgrade project.
My primary goals for this upgrade were to integrate several key features that would significantly improve the C11’s handling and setup versatility. These included:
- Utilizing the robust alloy rear end and axle from a Tamiya F104.
- Incorporating side dampers for enhanced stability and cornering.
- Implementing symmetrical steering turnbuckles for precise and balanced steering response.
Crucially, I aimed to establish an independent center damper setup, isolating it from the T-Bar’s influence. This separation would allow the T-Bar to exclusively manage the car’s roll behavior, while the center damper could be fine-tuned independently. To achieve this, a split T-Bar design, borrowing components from the TRF102, became essential.
The transformation required a comprehensive redesign of several key components. I machined a new lower front chassis plate to accommodate the repositioned servo, redesigned the T-Bar to facilitate the split functionality, and fabricated custom mounts for the side dampers. The servo repositioning, while necessary, does mean that the shortest wheelbase setting is no longer achievable with a standard low-profile servo.
This extensive modification project unlocks a range of setup adjustments, allowing for precise optimization of the Mercedes Benz C11’s handling characteristics. The enhanced setup options now include:
- Fine-tuning of the center damper’s spring rate for precise bump and rebound control.
- Droop adjustability, enabling optimization of chassis roll and weight transfer.
- Rear ride height adjustment using the bushings from the F104, for adapting to various track surfaces.
- Side damping adjustment, crucial for managing chassis roll and stability during cornering.
- Roll stiffness adjustment via the T-Bar front part screw, allowing for further fine-tuning of handling.
All custom parts were meticulously machined from high-quality 2.5mm and 1.5mm carbon fiber, ensuring both strength and lightness. For the T-Bar’s front section, I developed two versions: a softer FRP variant and a stiffer carbon fiber option, providing flexibility in tuning chassis stiffness. The small upper FRP part on the front was also upgraded to a 1.5mm carbon fiber component for enhanced rigidity.
The side dampers I incorporated are spare parts from a Serpent F110 SF4 formula car, while the center damper is the reliable TRF Damper for the F103. All alloy and fiber reinforced rear components and the axle are also TRF parts, ensuring high performance and durability. For the front, I utilized fiber-reinforced wheel hubs. To accommodate larger ball cups for the steering, I upgraded the ballheads to those from a DT-02 (Tamiya part number 9804154), a modification inspired by another Group C project I had seen.
The initial track test of the upgraded Mercedes Benz C11 took place on an indoor carpet circuit. I equipped it with a Hobbywing 21.5 G3R motor and a Hobbywing Xerun X10 Handout Spec ESC. The car’s performance was immediately impressive. Even the relatively simple front suspension, with limited setup options beyond spring changes, performed admirably right out of the box.
Looking ahead, I am considering upgrading the front suspension to a more advanced, state-of-the-art system to further refine handling. A question remains regarding battery life when using a more powerful 13.5 motor. If sufficient run time can be achieved, this chassis would be ideally suited for Pro 10 race events, which commonly utilize 13.5 blinky setups. Exploring high-capacity Lipo stick packs, perhaps around 6000mAh, with suitable C-rates might be necessary. Any recommendations on where to source such batteries would be greatly appreciated.
For those interested in replicating this upgrade, here is a comprehensive list of parts used:
- 1x Custom made 1.5mm carbon motor pod
- 1x Custom made 1.5mm FRP or carbon T-Bar
- 1x Custom made 2.5mm carbon front lower plate
- 1x Custom made 1.5mm carbon front upper plate
- 1x Custom made 2.5mm carbon outer damper mounts
- 1x Custom made 2.5mm carbon inner damper mount
- 1x Custom made TPU Bumper
- 1x Tamiya 54166 – Aluminum motor mount F104
- 1x Tamiya 84173 – Steel Axle
- 1x Tamiya 3450157 – Spacer rear axle
- 1x Tamiya 54158 – F104 Aluminum Diff Housing
- 1x Tamiya 54215 – Spur gear adapter
- 1x Tamiya 54330 – Carbon reinforced c-parts
- 1x Tamiya 50591 – ball collar
- 1x Tamiya 53901 – TRF Special Damper
- 1x Tamiya 3450707 – Rear Hinge Cover
- 1x Tamiya 3450705 – Rear Hinge A
- 1x Tamiya 3450706 – Rear Hinge B
- 1x Tamiya 9804360 – Shaft
- 1x Tamiya 9804889 – Flanged Tube
- 1x Tamiya 9805777 – Screw
- 1x Tamiya 54154 – Carbon reinforce front uprights (optional)
- 1x Serpent 411360 – Side tubes
- 2x Tamiya 9804154 – Ball connector 5mm
- 1x Fenix G56-1345 – Steering turnbuckles 200mm or similar
- Various M3 screws
- 5mm Ball connectors and ball cups
This upgrade project has significantly enhanced the performance and adjustability of the Mercedes Benz C11, making it a more competitive and enjoyable RC car to drive. The blend of custom-designed parts and high-quality Tamiya and Serpent components has resulted in a chassis that is both refined and robust, ready to tackle the challenges of high-speed RC racing.
