How to convert an on-road RC car to off road? – Tamiya TT02 review

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Setups for the Versatile Tamiya TT-02 chassis

 

Do you still remember what your first RC car was?  I bet it was a Tamiya TT02.  You can choose to get it as a reasonable priced RTR or assembly kit on Amazon.   There are tons of option parts or even conversion kits from different brands such as 3 Racing, Eagle Racing, Yeah Racing, GPM and Active Hobby. With a reinforced chassis plate, carbon fiber shock towers and aluminum parts, you can build this chassis in anything you want. Drift, touring, rally, street build are only a few popular choices for any creative RC hobbyist. Many people with advanced skills have unique builds based on this reliable chassis for its simplicity of the design.  Let’s see why this chassis has its way to to the most popular chassis of all time.

 

Fig.1 Working on my second TT02 during 2018+

On-road Performance:

As the chassis is mainly for on-road performance, it is very easy to build as a street cruiser or a touring racer since it has all the basics of a good 4WD car. Shaft driven means fast acceleration and simple geometries all over the chassis, making it easy to maintain and service.

However, due to limited size on the gearing cover, it doesn’t allow you to run any spur gear higher than 84T(bigger) while putting too much power on a basic chassis will create stress on small components like shaft cover/ stopper and the main shaft, causing failure to the gearbox.

Although you may still mount a 5.5T motor on it, it may not allow you to run a high gear ratio (low speed with higher torque) due to direct contact on the shaft creating too much torque causing the motor and the ESC overheat. From an experiment done by myself, it is not recommended to use any brushless motor with a rating lower than 9T as you may have a chance to shatter your plastic spur gear.  For all these reasons you will not have much fun racing your TT02 against any modified RC car with a 5.5t motor.  This is the main weakness of TT02.


Fig. 2-3 This is my first TT02 Street/ Drift build

On the other hand, as the advantage mentioned above, the TT02 can also be a good 4WD CS(Counter Steering) chassis for drifting due to excellent acceleration so they can have insane speed when exiting a corner.

As the picture above indicates, you can gain more steering angle from installing a Fastrax or Yeah Racing Front end components which includes aluminum upper and lower A-arms, aluminum knuckles and aluminum steering rack, increasing the availability of the steering.

As hard rubber tires will be used in drifting, it allows you to use high-speed motors as my first TT02 has a 60A, 9T brushless motor installed for the finally drift build.  The drifting surface is slippery so it allows the car to run a faster motor without creating too much load.

Fig. 4 My street build waterproof TT-02

Tamiya TT02RR

Tamiya tt02RR is the newest release of TT02 that is race ready. Tamiya has added a lot of racing features to this car.

Off-road Performance:

You may find some Tamiya TT02 kits comes with a set of semi purpose tires and an off-road style body shell such as the Toyota Gazoo Racing Yaris rally spec, Lancia Delta, Subaru Impreza Monte Carlo ‘99 to satisfy off-road or rally fans. It is possible to convert an on-road chassis into an off-road vehicle thanks to its reliable base chassis which can take impacts from jumps and rough terrains. Many RC enthusiasts can tell you how good the TT02 can be based on basic performances so, in order to make it an off-roader, you should consider replacing parts as follows:

For turning your TT-02 into an off-roader, you also need 4 rally block tires. The best you can get is Tamiya 50476. However, with these bigger tires, you need to make sure that your body shell is suitable for these tires.

A good set of shocks can provide major improvements on the performance so changing the shocks that are longer than the stock ones should provide more ground clearance and acquiring more suspension travel. This will make the vehicle easier to handle any rough terrains. I recommend acquiring some 55mm to 60mm (hole-to-hole) shocks to achieve it.

However, due to design purposes, the front has less down travel on the A-arms; it means no matter how much longer the newly acquires shock is, as compared to the original one, you will not get more suspension travel once A-arms hit the bottom position which is limiting the downward movement of the A-arms. This may affect the vehicle running on rocky roads as the front of the chassis will have a chance to hit the ground. To solve this problem, you may customize the chassis to allow the A-arms to gain more travel but this will require more technique so this modification may be not recommended for beginners.

Besides, with longer shocks,  TT-02 will get a decent amount of travel on the rear as the ground clearance for the back can go up to approx 12mm. By having this amount of travel, you will have more than enough travel to go through jumps and crests.

  • Drivetrain

As off-road driving requires more torque to push the vehicle on rough terrains, running low gear (A smaller pinion with larger spur gear)is a must since higher gear (A larger pinion with a Smaller spur gear) will create more load on the electronics means overheating will be a problem. To maintain a good gearing, it would be around above 3.46 to be ideal as base reading. The formula is as follows:

Spur Gear (T) / Pinion Gear (T) = Base Gear Ratio

As someone will calculate the gear ratio with the internal gear ratio (2.6) but you will mainly need the base gear ratio only for a reference.

If you use the stock spur gear, you will need a pinion gear with 20T.

On the other hand, the stock center shaft is made out of plastic while supporting a torsion motion, reflecting the shaft will bend easily due to directly driven by gears. To concur the issue, simply replace it with an aluminum center driveshaft in order to reduce the bending caused by the torsion motion on the shaft.

Besides the center driveshaft, the stock differential has a relatively thin grease but not enough for rough terrain driving, causing it to lose speed over bumps. Thin differential grease oil means having a more open differential so there will be more resistance on the power delivery to the wheels since the differential will eat up the power. Putting thicker differential oil will help get the vehicle up to speed with the help of the gears. This means the differential is locking up to create more power to the wheels overcoming the resistance of the ground surface. However, if the differential oil is too thick, means almost fully locking the differential, will make the vehicle undrivable due to having a slidey rear end or an understeer front end. So you may have to try putting differential oils on different ratings to get the best fit.

This may vary to different purpose on what the owner wants the vehicles to do. Off-Road driving includes more natural environment elements. You may consider replacing the stock electrics to splash-proof or waterproof ones such as the Hobbywing Ezrun Max10, Hobbywing Quicrun 1060, Hobbywing Quicrun 1080 and Axial AE-5.  With some ESCs, you can use either a LIPO or an NIMH battery.

For the motors, brushed motors are waterproof so feel free to mount them on the TT-02. However, you may want to be careful in selecting a brushless motor as only some of these brushless motors are splash proof or waterproof. There will be tags on the box indicating its waterproof function or with a code ‘WP’ as a hit referring the function. These hints can be applied to buying a servo for your build as well.


Fig. 5-6 Tags are placed on the box to verify the electronics are waterproof

Tamiya TT02 Off-Road Car

Dust Cover

If you are driving your Tamiya TT-02 off road in a sandy road, you might want to have a dust cover so that your racer’s electronic system will not be damaged by small rocks. The dust cover can be purchased here They are shipping internationally.

Miscellaneous

  1. Shell post

This is an application to support the body shell from the chassis which prevents the body shell or anything hitting the chassis, causing damage to any of the components. However, it will be a bit annoying to put on the body clips every time to hold the body shell in place so some of the brands have invented invisible body mount which uses magnets to hold the body. Here are some advantages and disadvantages of both body shell mounting methods.

With a shell post Without a shell post
Requires to drill holes on the body shell Easy mounting
Lack of scale looks Looks like a real vehicle
Have to be precise on drilling holes Easy to line up the body shell on the chassis
Can take impacts without the bodyshell flying off Easy to rip off the shell during high impact
Mostly comes with the chassis, no extra cost Comes with different color and styles
Plastic Aluminum support
Cheap Relatively expensive

Using alternative methods seems to be a better solution than shell posts. However, this may differ to people as shell post are mainly use on touring RCs since the shell will help to increase downforce by aerodynamics so having a shell post can ensure the shell doesn’t shift causing unstable handling during high speeds.

In addition, shell posts usually come with the kit or RTR and they are cheap to replace as well. Despite having excellent stability, shell post will need you to drill holes through the shell which affects the realism of the shell, especially you spend loads on shell accessories. In this case, you would like to buy a magnet body mount which the magnets will hide under the body shell which would not affect the looks of the body. However, there are drawbacks like some of them are in bad quality which will easily be ripped off from an impact.

Fig. 7 An example of an invisible shell mounting 

Materials of gears

When you decided to buy upgrade parts for your vehicle, you will certainly consider changing pinion or spur gears to suit different surface grip levels. You will find gears that made out of four main materials, plastic, steel, titanium and aluminum. These materials are good for making gears since they are stiff but brittle means they can handle loads easily but will snap off easily if too much load has been applied.  Manufacturers producing gears in different materials because each type of material suits each type of vehicle you purchase the gears for.  For example, the gears for a touring car need to be light and handle less torque since the gears are constantly moving so the plastic would be a good choice.  On the other hand,  drift cars will lock up the gears in a sudden to perform an E-brake maneuver which will affect the gears in a different way. We will have a deeper look at what to consider what buying gears.

Wear

As mentioned above, gears will wear due to sudden movements of the throttle causing the gears to lock up. Despite all gears will wear anyway through time, it is always recommended to have a metal pinion gear and a plastic spur gear as plastic are polymer reflecting they are more flexible than metal. Wear will be minimized as plastic can absorb extra load in sudden movements while metal to metal gears will straight up grinding the gears which are not ideal to the drivetrain. By applying the same theory to internal gears in the gearbox if the vehicle is direct driven instead of belt driven, gears should be in a combination of plastic and metal to prevent overloading.

Note: As 3D printing is building its way up to a trend which you can make everything at home, it is not recommended to 3D print gears due to lack of rigidity of the material. They are not for high-stress use unless forging expensive materials from shops. But this will cost you more than just buying one.

Price

This depends on the materials of the gear. It is usually made of plastic, aluminum, steel, titanium from the cheapest to the most costly. You will find them relatively cheap in an average from 6 USD to 13 USD as manufacturers know RC enthusiast will purchase different gears since gears are consuming items so manufacture produce them with a low cost.

Fig. 8 Material of gears (from left to right): plastic, aluminum, titanium, plastic

Screws

It is a good idea to replace all the screws with stainless screws so that you will not be worried about your car when you drive it over water.

Conclusion:

To sum up the settings on the TT02, it is an excellent chassis to expand your creativity while having limitations such as gear ratios and motor limits, preventing you overdone your project. Saving yourself more money to necessary upgrade parts like aluminum center drive shaft and aluminum front-rear A-Arms and knuckles to release the true potential of the chassis. Pick up a good set of electronic is always good to do, providing a longer lifetime for the chassis. Tamiya TT02 is the best starters RC car I would truly recommend newcomers to purchase.

 

Thanks for reading
Writer: Kelvin Wong
Edited by Carlos Santos, your webmaster.