Tamiya developed a completely new 2WD off road chassis from scratch, there are no parts in common with the previous on-road chassis. The chassis was used on two different models, the XR311 and the Cheetah, both with real-world military jeeps as role models.
The XR311 chassis is made of aluminium with independent double wishbone suspension. The movement of the A-arms is distributed to the 4 torsion bars acting as the only dampening parts. There are no actual dampers. The front suspension system also contains the steering assembly and the gear/motor assembly is located in the rear, all made of plastic material. However, this system was strong enough for gentle off-road use.
The engine is installed in the rear on top of the gearbox with easy access to change gear ratio improving speed or power.
The wheels are soft and help the suspension in absorbing bumps in off-road use.
The body of both models is very rich in details such as rear-view mirrors, lights, front winch, gasoline cans, axe, shovel, and the driver figure. The driver was the same for the two models except for a different head.
The chassis appears robust and suitable for off-road use, but in reality some parts easily break.
The plastic torsion bars are the weakest point of the XR311 chassis and body details were easily lost when driving, in particular rear view mirrors, and the details in the back.
There is no protection against water or mud, the battery is housed inside the center frame, the receiver and its battery are installed in the two side wings of the center frame, the steering servo is installed vertically without any protection just like the rear mounted MSC servo.
Two models use the XR311 chassis:
- The XR311, item number 58004 released for sale in 1977 and available on the market until 1982 as the original kit.
XR311 was developed by FMC as a prototype for U.S. Army in the early 1970s, it competed with prototypes such as Lamborghini's Cheetah and AM General’s Humvee (this was the vehicle chosen to replace the M151 jeep).
At least two series of the XR311 model were tested, and it was produced in a dozen pieces in total.
The military even tested the various solutions with different armaments such as missiles or machine gun system.
- Lamborghini Cheetah, item number 58007, released for sale in 1978 and available on the market until 1983.
The Cheetah was developed as a prototype for U.S. Army by Lamborghini in the 1970s. The few examples built were destroyed or not completed, U.S. Army did not accept the design which was limited by the low power of the engine and the 3-speed gearbox, it did not provide the necessary off-road performance.
Lamborghini's LM002 takes several aesthetic and technical solutions from the Cheetah.
Detailed differences between the originals, moving from front to rear of the chassis:
XR311 and Cheetah have completely different body. The color of XR311 is olive drab instead the color of Cheetah is light sand. In the instruction manual of the Cheetah, there are several colour solutions available, which ranged from camouflage colour with spots to the tricolour of the Italian flag.
Both XR311 and Cheetah have soft tires with a completely different design. XR311 re-release has the same tires of original one.
The Cheetah is shorter than the XR311, the difference is 10 mm obtained easily using different screw holes (2+3 instead of 1+2) in the aluminium chassis.
- Front bumper
The bumper is black colour for XR311 and Cheetah, but the shape is completely different
- Front guard
The Cheetah guard is black while the XR311 is just aluminium. The shape of the front guard is also different.
Tamiya has re-released the XR311 58004 twice and has since the first re-release in 2000 been more or less available in the market. The Cheetah has not been re-released as per January 2023.
There are some differences between the original and the re-release. The body has been slightly changed, but the most noticeable changes has been made to the chassis.
- Metal parts
Again, a lot of smaller changes including in the main chassis, but most obvious are the new battery and received holders, now more suitable for modern electronics.
- Rear axle system
Original and re-release has different drive shafts and joint cups.
- Gear box cover
Original and re-release has different black plastic cover gear box
- Front and rear torsion bars
Original has one piece plastic torsion bar, re-release has metallic torsion bars with plastic end brackets. The attachment to the A-arms is also different on the re-release.
- Skid plate and front guard
Original and re-release skid plate and front guard are completely different. There-release is similar to the original Cheetah version.
- Plastic parts
Many smaller changes to the chassis plastic parts of the gearbox
As with many re-releases the XR311 lost some of it’s side markings in the 2000 re-release.
Bots, nuts and other hardware has been upgraded from flat head screws to more modern Phillips screws and self-locking nuts.
- Speed controller
The original came with a slider type MSC while the reissue came with a ESC.
Written by Gabriele Andreoni