Car Settings (Part 2) - Tamiya RC Start Guide
03 December 2024
Car Settings (Part 2)
There are many different types of circuits, such as technical courses with many corners and high-speed courses with many straight lines. Setting up a car to suit such a circuit is what we do. By incorporating a wide range of spare and optional parts, you can greatly change the handling characteristics of your car.
Choose to read the topic you interest.
8. Wheel alignment
Wheel alignment indicates how the wheels are attached to the road surface. Typical items include toe angle, caster angle, and camber angle, and the settings of these also affect steering characteristics.
- Toe Angle
Toe angle is the angle at which the left and right wheels taper forward (toe-in) or backward (toe-out) from the center line of the chassis when viewed from above. Increasing the toe-in of the front increases the straight-line stability but tends to understeer, while toe-out improves response because the inside tire cuts in deeper from the start of cornering, but tends to decrease straight-line stability. The rear toe angle also affects the behavior when cornering, and weakening the toe angle leads to a tendency to oversteer, while strengthening it leads to a tendency to understeer. Toe angle adjustment is generally done by adjusting the length of the steering rod in the front, and for fine setting, it is recommended to replace it with a turnbuckle type shaft (some chassis are equipped as standard). In the rear, it is generally done by replacing it with a toe-in rear upright. Regardless of whether it is front or rear, extreme toe angles increase the resistance on the tires while driving, causing extreme tire wear and impaired driving stability, so it is generally adjusted within the range of -1 to +1 degrees for the front and 0 to +3 degrees for the rear.
OP.1549 TT-02 Aluminum Rear Upright (2.5 degrees) - Caster Angle
The angle at which the kingpin that supports the front wheels is tilted backward is called the caster angle. The larger this angle, the more the machine will move in a straight line, but the machine will respond more gently when you turn the steering wheel. Also, if the caster angle is too large, it can have adverse effects such as uneven wear on the inside of the tire and reduced grip. Also, if the vehicle height is different between the front and rear of the vehicle, the caster angle will change accordingly, so be careful.
- Camber angle & camber angle change The angle of inclination of the tire to the left and right when viewed from the front and rear of the chassis is called the camber angle. If the tire is in a V-shape, it is negative camber, and if it is in an inverted V-shape, it is positive camber. In double wishbone type suspensions, which are common in RC cars, the camber angle is adjusted by the length of the upper arm. If the upper arm is shortened, the tire will be in a V-shape (negative camber) when viewed from the direction of travel of the vehicle, increasing grip when cornering, but if the angle is too large, straight-line stability will decrease, so it is usually adjusted to around 0.5 to 1.5 degrees. In addition, in general machines, the upper arm is shorter than the lower arm, and the camber angle becomes stronger when the suspension is compressed. Depending on the chassis, multiple mounting holes are provided on the mounting part of the upper arm on the chassis side to adjust the amount of this change, and by using this to change the length of the upper arm, you can season the characteristics when cornering. If the upper arm is shorter than standard, the fluctuation of the camber angle when the suspension moves will be large, making the behavior when cornering quicker. Conversely, if the upper arm is longer, the change in the camber angle will be suppressed and the car will be more stable. The same effect can also be achieved by adjusting the height of the upper arm mount with a spacer; a higher position will result in more fluctuation in the camber angle when the suspension moves, while a lower position will result in less change in the camber angle.
Mounting holes used to adjust the upper arm length TA05ver2 has four mounting holes.
OP.861 Touring Car Camber Gauge (ITEM 53861)
A special gauge that allows you to check the camber angle at a glance.
9. Wheelbase and track
The wheelbase is the distance between the front and rear wheels, and the tread is the distance between the left and right wheels. If the tread is the same, the longer the wheelbase, the better the straight-line stability (the harder it is to turn). Conversely, if the wheelbase is the same, the wider the tread, the sharper the cornering. Some touring cars, etc., allow you to adjust the length by rearranging the spacers in the suspension shaft or rearranging parts (such as the M chassis), so you can adjust the length of the body to match the body you are using, and change the running characteristics of the vehicle. To widen the tread, you can use wide wheel hubs or spacers, or use wheels with different offsets, but be careful when making the tread too wide, as the suspension may come into contact with the body when it sinks, or it may violate the width limit of the race regulations.
SP.1263 5-twin spoke wheels (black) x 4 (26mm/+4)
If the standard wheels in the kit have an offset of +2, changing to wheels with an offset of +4 will widen the tread by 2mm on the right and 2mm on the left, for a total of 4mm. Note that there are two types of tire widths for touring cars, medium narrow and narrow, so when purchasing, be sure to pay attention to not only the offset value but also the tire width.
- Toe angle/tread change with suspension mount
In some touring cars, such as the TA07, the toe angle and tread can be changed by replacing parts called "suspension mounts" or changing their installation direction. Suspension mounts are parts that secure the suspension arms to the chassis. By making the front and rear suspension mounts different in width, the toe angle can be changed, and by making them longer or shorter, the tread (vehicle width) can be changed. When the tread is changed with the suspension mounts, the distance between the left and right suspension shafts that secure the suspension arms changes. If the distance becomes narrower (using a narrow suspension mount), the body will roll more easily, and if the distance becomes wider (using a wide suspension mount), the body will roll less easily. Suspension mounts are also available in different heights and with spacers for adjusting the height. If the suspension shaft is attached higher, the body will roll less easily, and if it is attached lower, the body will roll more easily. By selecting a suspension mount with these characteristics in mind, it is possible to control the amount of body roll while keeping the tread constant.
OP.1074 TB-03 Aluminum Suspension Mount (1F) (ITEM 54074)
OP.933 Aluminum Suspension Mount Spacer (1mm) x 4 (ITEM 53933)
10. Suspension
In real cars, the role of the suspension is to improve the ride comfort, but in RC cars, the important role is to absorb vibrations caused by unevenness in the road surface, keep the tires on the ground, and maximize the grip. If there is no suspension or the suspension is too stiff, the car will bounce over small bumps in the road surface, and the tires will leave the road surface and will not be able to grip. On the other hand, if the suspension is too soft, the springs will compress when a shock is received, and the result will be the same as if there was no suspension. In addition, since the force applied to the suspension changes depending on the cornering speed, it is also important to consider which section to prioritize when setting the suspension, such as low-speed corners, high-speed corners, or straights. Identify the characteristics of the course and the machine and find the setting that will allow you to record the best time. Suspension settings are full of the fun that is unique to motorsports.
- Suspension type
Double wishbone type four-wheel independent suspension is often used in RC cars. The double wishbone type has a structure in which the four tires can move up and down separately, and is characterized by its excellent ground contact and wide range of adjustment options. The structure is composed of an arm that connects to the frame so that the wheels can move up and down, a spring that supports the arm, and a damper. Some machines also use a pushrod type inboard suspension, which has the same basic mechanism as a real racing machine and has excellent aerodynamic properties. This type of suspension arm is composed of A-arms on both the top and bottom, and the movement of the lower arm is transmitted from the pushrod to a part called an L-shaped rocker arm, which expands and contracts the damper unit.
Double wishbone suspension (DF-03Ra chassis)
Inboard front suspension (TA05-IFS chassis) - Determine the spring strength
In RC cars equipped with suspension, the weight of the car is supported by coil springs. Therefore, the spring stiffness is selected according to the weight of the car. When assembled according to the instructions, the weight of the car and the springs are balanced, but the important point is that "the weight of the car is not constant." If the car body is made lighter, the springs must be weakened accordingly, and the weight of the battery also varies depending on the type. On the other hand, if the speed of the car increases due to a motor replacement, the load applied when cornering also increases, so with standard springs, the outside springs may be fully compressed (the inside springs may be fully extended) when cornering. In such cases, it is necessary to select springs that can withstand the load, but if they are too hard, they will not be able to absorb shocks from the road surface, so it is important to determine the spring stiffness. Note that it is not always best to have the same spring stiffness on the front and rear. Changing the spring stiffness on the front and rear will also change the driving characteristics, so it is a good idea to use an optional spring set to check the change in behavior.
OP.927 DF-03 Setting Spring Set (ITEM 53927) - Damper installation angle ≒ spring stiffness
Some RC cars allow you to adjust the damper mounting angle. Changing this angle increases or decreases the force on the spring, ultimately having the same effect as replacing the spring. Basically, laying the damper flatter will make it softer, and setting it up will make it stiffer, but this change is more gradual than replacing the spring, so it's good to use it for fine adjustments. For inboard front suspension (IFS) types, you can achieve the same effect by changing the thickness of the spacer attached to the rocker arm.
DB01 Chassis Front Damper The damper angle can be adjusted by selecting the mount installation position. - The damper matches the spring
Coil springs repeatedly expand and contract when subjected to impact from the road surface, so the springs alone cannot stabilize the vehicle body. Therefore, dampers are used to quickly stop the expansion and contraction. - Oil damper
Oil dampers are often used in RC cars. The cylinder of the damper is filled with oil, and the piston moves up and down through the oil to control the expansion and contraction of the spring. The piston has small holes (there are also types without holes), but the more holes there are and the larger the diameter of the holes, the less resistance there is and the smoother the piston moves up and down, making the damper softer. When the damper is soft, it can better follow the road surface, but its ability to suppress vibrations is weakened. With this in mind, the basic idea is to set it harder on flat roads with good grip, and softer on other roads.
TRF Special Damper (Hard Black Coat) x 4 (ITEM 42102)
Example of the number of holes in piston parts (3-1-2 from the left) - Damper oil
The effectiveness of the damping can be adjusted not only by the piston holes but also by the oil itself, and various optional parts with different viscosities (stickiness) are available, such as medium, hard, and soft. When setting up an oil damper, major adjustments should be made by changing the presence or absence of holes in the piston and the number of holes, and fine adjustments should be made by changing the viscosity of the oil. The lower the viscosity (softer) the oil, the easier it is for the piston to move. The viscosity of the oil also changes depending on the temperature, so you can maintain consistent conditions by choosing a softer oil when the temperature is low and a harder oil when the temperature is high.
OP.444 Silicone Damper Oil Medium (ITEM 53444) - Another factor that the damper determines is the vehicle height.
The damper unit also allows you to adjust the vehicle height, which is an important factor that affects the characteristics of the vehicle. Vehicle height is the height from the road surface to the bottom of the chassis. When checking the vehicle height of an RC car, load the machine with all the equipment you will be using when driving, such as the battery, place it on a flat surface, and move the suspension up and down several times to allow it to settle before checking. You can check with a ruler, but for more accurate settings, we recommend using dedicated items such as a height gauge or height and droop gauge. Basically, lowering the vehicle height will increase stability during driving, as the center of gravity will also be lowered when the vehicle height is lowered. However, if the vehicle height is too low, there is a higher risk that the bottom of the chassis will hit the road surface and suddenly lose grip when the vehicle rolls during braking or cornering, so it is necessary to determine a height that will not bottom out while taking into consideration the smoothness of the road surface, the hardness of the springs, the vehicle speed, etc. Adjusting the vehicle height is generally done by adjusting the amount of spacer placed between the damper and spring, or by changing the position of the cylinder nut, and it is possible to adjust the vehicle height to a certain extent (see the diagram on the right) while keeping the spring stiffness constant. Note that changing the spring stiffness will change the amount of sagging, which will ultimately change the vehicle height, so be careful of this as well.
OP.862 Touring Car Height & Droop Gauge (ITEM 53862) - Rebound stroke adjustment
Chassis such as the TA05 are equipped with a mechanism that allows adjustment of the "rebound stroke." The rebound stroke is the amount by which the suspension sinks when stationary. To measure it, the vehicle is placed on a flat surface and gradually raised to the height where the tires do not leave the road surface. The value obtained by subtracting the normal vehicle height from this value is the rebound stroke. A large rebound stroke allows the suspension to move well, so stability during driving is increased on low-grip surfaces. On the other hand, the vehicle's posture changes are large, so grip may be lost during cornering when driving at high speeds on high-grip surfaces. In addition, the rebound stroke can be adjusted separately for the front and rear, just like the vehicle height, allowing for fine tuning. More front stroke tends to cause oversteer, while less stroke improves responsiveness but causes understeer. In addition, more rear stroke tends to increase driving stability.
การปรับจังหวะการเด้งกลับ (TA05verⅡ/ด้านหลัง)
Rebound stroke adjustment (TA05verⅡ, rear) The amount of stroke varies depending on the conditions, but it is generally adjusted from 3mm to ±2mm. - stabilizer
As cornering speed increases, the vehicle body tends to lean outward (roll) and sometimes the inside wheel lifts off the road surface (in-lift), making the vehicle unstable. Stabilizers are used to reduce the amount of roll and sharpen the handling. While replacing springs affects both the amount of roll and the amount of forward/rear sway (pitching) that occurs during acceleration and deceleration, stabilizers can only limit the amount of roll, making them useful when adjusting cornering behavior.
OP.1239 M-05 Stabilizer Set (F, R) (ITEM 54239) - The best way to understand suspension settings is to practice!
The old rule of thumb for RC car suspension settings is that the springs should compress a little when the car is parked quietly, and should return to their original position when you hold the car down and release it. However, this is only a guideline when the car is stationary. A car in motion is subjected to various forces in each situation, such as acceleration, deceleration, and cornering, and the direction and angle of inclination change constantly. Therefore, it is impossible to find a setting that best fits every corner unless you change the suspension settings in real time while driving, like the old F1 cars. To master such suspension settings, practice is better than theory. Try changing the settings little by little on the circuit, feeling the changes in each section, such as "This is how it changed at the entrance to a low-speed corner. This is how it changed at the exit. In a high-speed corner, on a straight line..." and searching for the setting that gives you the most comfortable ride will help you improve faster than understanding theory at a desk.
Williams FW14B Renault (โมเดลมาตราส่วน 1/12)
Williams FW14B Renault (1/12 scale model) This is the F1 car that won the Grand Prix title in 1992. It is known as the car that introduced active suspension, where the suspension settings change to suit each section of the circuit.
