Your First Kit
Your First Kit
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The Basics- Understanding Chassis Types
Selecting your first kit can be overwhelming as there are so many different styles of machine you can build! But it can be helpful to know some fundamentals that can simplify and inform your decision as you jump in.
Underneath the shape of the body and the color of the parts, machines are actually distinguished by their chassis type. There are seven currently available chassis designs and each have slightly different properties on the track due to their attributes. As a simple overview:
Weight will affect the acceleration and top speed of the machine.
Outer dimensions and wheelbase length will affect how the machine performs in turns.
Ground clearance and motor location will determine the machine’s center of gravity, which will affect different aspects of cornering and how it lands jumps
Chassis rigidity affects nearly all performance aspects of a machine in small ways that can have large impacts. Understanding when it matters can be a bit of an art, but it helps to be aware that the chassis types differ in how much and in what ways they will flex.
Chassis Types by Weight and Footprint
As a simple reference, this chart compares the available chassis types by base weight (does not include body, rollers, etc) and outer dimensions (shown as area- the product of the outermost length x width). Motor location is shown to indicate if the center of gravity is forward, rearward, or neutral.
For a visual guide to the chassis types, check out the Tamiya USA Chassis Guide
Note: this guide has listing for a few out of production chassis types and it lacks a listing for the recently introduced VZ chassis.
For those who want to get into the details with precise specifications, check out the Tamiya Japan Chassis & Compatible Parts Catalogue
Note: This catalogue has numerous legacy chassis types that are no longer available for purchase. Additionally, please take note that Tamiya Japan does not sell directly to the US
Digging Into Properties, Performance, & a Bit of Physics
Digging Into Properties, Performance, & a Bit of Physics
Let’s look at an example of how chassis differences can affect a stock machine’s performance on the track. The impact of weight seems simple: the lighter the car, the faster it should go. In actuality, a lighter car has more acceleration because it is more easily acted upon by a force. When we think about the machine passing through a turn, we know a a lighter car will have more acceleration coming out of a turn because the motor will be able to accelerate a lighter car more effectively. However, the same property that results in more acceleration coming out of the turn will mean more deceleration going into a turn. Therefore, a heavier car might move faster through a turn due to its increased momentum, which depends on earlier track condition and how much speed the machine had built up prior to the turn.
Determining what property, accelleration or momentum, would benefit a machine will largely depend on portion of track follows the turn in question. If the turn in the example is only the start of a series of S-turns, a machine with too much speed could course out (leave the track) as it tries to respond to the quick turns. Here, too much speed is a bad thing. Such a situation could favor a lighter car that would decelerate into the series of turn, move safely through, and then speed out. But, it is then important to note that weight is not the only attribute that impacts the machine’s performance and controlling speed is not the only way to tackle a tough series of turns. For example, a rigid chassis with a wide footprint and a low center of gravity might be able stay on the track through the at a higher speed. The actual outcome of either example will depend on more than just these attributes alone.
The the interaction of the chassis attributes with track conditions (and tunable machine settings) are what the racer must evaluate to determine where their machine might be advantaged or disadvantaged by a track. Ultimately, no single chassis type is better than the others in every section of every track. Taking into account both the advantages and disadvantages of their machine as they pertain to a particular track requires a racer to understand the impact that the base chassis attributes can have on the three key performance factors: velocity, acceleration, and stability.
Selecting Your First Kit
Now that you know the basics about chassis types, it is time to select and build your first kit. Which properties you choose to prioritize are ultimately a matter of personal preference or inclination. Once you select the chassis type(s) that seems most sensible there are a few more things to consider that can help you narrow your kit selection even further.
Wheel Size & Gear Ratio- Small wheels and large gear ratios (e.g. 5:1) will have more acceleration and power to push through turns or inclines. Large wheels and small gear ratios (e.g. 3.5:1) will have a greater potential top speed.
Tire Type & Cross-section- Soft tires grip harder in the corners, benefitting cornering stability at the expense of turn speed and smooth landings after jumps. Hard tires allow the wheels to spin when there is an excess of force, like occurs in a turn, resulting in faster speeds through the turn. The cross-section of the tire determines how much contact the tire will have with the track and will have similar impacts on cornering.
Extra Bits- Some chassis types or individual kits come with special parts. For example, MA chassis kits typically come with a rear brake and kits in the Laser Series all feature additional stabilizers. One of these parts might help your decision. So, look closely!
Example of typical information shown on boxed kit/product listing.
Want More Info About Settings?
Want More Info About Settings?
By considering the points above, you have just dipped your toe into tuning the settings of your machine. Tuning is where things become even more fun! There are many guides out there that can help you learn about the impacts differences in machine settings can have, but here are two useful overviews to help you understand the basics.
Still don't know which kit to get?
Just jump in!
Grab the kit(s) you think look cool with the chassis type(s) that seem sensible to explore first. Experience their assembly and try to tune them for their best performance right out of the box. As a metric, you can come out and run a Box Stock time trial to see how your build compares to other Box Stock cars.
Note:
Kits that have upgrade parts in the box such as upgraded motors (listed as XX-Tuned or XX-Dash), metal rollers, mass dampers (brass weights on the outside of the kit), stabilizers (black fiberglass plates on the front or rear), or polycarbonate (ultra-lightweight clear) bodies are not eligible for Box Stock competitions.
Event Specific Note:
The only relevancy of class restrictions for the upcoming Track Day is which Time Trial your machine will post to should you participate. Times will be posted for cars divided into in Box Stock and Open class. More simply put, cars will either qualify to run a Time Trial as Box Stock, or else they will compete in the Open class with all other machines. See the event details for more information.
If you want more customizable kit that can compete at higher speeds with the addition of upgrade parts, consider one of the starter kits that comes with upgraded rollers and a Tuned motor. Alternatively, you can find the matching Basic Tune-Up Parts Set for the chassis of a kit that interests you. These part sets include matching mounting plates, mass dampers, and additional rollers that give you additional tuning options. If you add a Tuned motor, you will be glad you had those additional options to help keep your kit on the track!
The choice is yours. Remember, the purpose of your first kit is to experience the building a machine and to see how simple changes can affect its performance on the track.
If you have any questions about kits, chassis types, or upgrade parts, feel free to contact us, and we will happily answer any questions you might have.
And remember, you can always bring your unassembled kit(s) to a track day and build your first kit together with us. We will have the basic tools available for general use, and there will be people willing to offer tips and help in getting your first kit together.
To the Track!
Once your machine is ready, it is time to put it on the track and test your build and tuning skills! Each Track Day will feature a new course layout to test your machine and challenge your ability to tune your car or even engineer a solution to conquer a difficult portion of the track. There is a ton to learn, and it is most fun to learn and experiment with others! Even if you don’t have a machine ready to race, Track Days are a great place to come hang out, learn what Mini4WD is all about, and see some cool cars conquering the challenges of a new and unique track.
With time, you will learn your machine(s) and be ready to compete in one or more competitive classes of your choosing. Or maybe you will want to tackle each and every new track and engineer a solution for your machine’s top speed. Either way, the track is the place to be, and we hope you will join us there!
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