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A RC requires many elements in order to create a superb handling. But this step is not as easy as it looks, a lot of fine tuning and rebuilding should be done. However the most important thing on tuning the vehicle is getting the suspension set up right. Some beginners think the powerful the motor, the faster the car will go. Unfortunately, this is a misunderstanding among the basics as more power is delivered to the chassis, the more you will break it or make it undrivable. This blog will bring you through the importance and essentials that you may want to know about suspension tuning.
What is Suspension?
A suspension is a system to absorb surface roughness when the vehicle going pass rough paths. It includes various components such as shock absorbers, springs, A arms, shock towers, wheel knuckles. These components will affect how the vehicle behaves based on different setups while these settings are all variable means every detail is always changing how the car handles. We will take a closer look into this later.
What can affect suspension?
As suspension systems are based on geometry, means the contact between the tire and the ground will affect by changing the angles and geometries in the system, giving different vehicle characteristics. These geometries are called camber, caster, arkman and toe. They have to work with the suspension systems or else you may find the vehicle difficult to drive. These small detailed elements are important when you want to push your vehicle to the absolute limit without have any weird handling. Things you may have to consider such as spring stiffness, shock rebound, shock angle and shock preload. They are all rated as a high priority to adjust in terms of fine tuning. Some people spend a long time to rebuild the shocks just to perfect the shock rebound by 2mm.
- Shock Oil
Shock oil can be represented in different ways by various brands so it is recommended to stick with one brand to prevent confusion on viscosity. This will be the second element you could modify through the whole suspension tuning process. It can change the characteristics of the chassis with distinct as the viscosity of the oil will change how fast the shock shaft moves through the shock body. As it will affect the shock rebound. By changing the shock oil, you can decide the speed of reaction on the shock, either fast or slow. The thinker the oil, the slower the shock piston travel, vise versa.
Fig. 1 I use Yokomo shock oil for all of my RCs
Shock shaft and o rings
These two main components are to ensure the stability of the shock. As o ring needs to stop shock oil leaking while keeping external substances out of the shock, so buying the correct o ring is crucial. On the other hand, the stock shock shaft should provide enough travel for the type of vehicles you have respectively but you can still modify it by changing the length of the shaft to fit the distance between the upper and lower arms. Create more droop or simply more travel.
Shock piston is to limit the amount of fluid that goes through the shock body. They usually have an option of 2, 3 or 4 holes. The more holes you have, the shock shaft will travel faster compare to a piston with less holes on it, making the shock reaction faster. If you want to get more grip from the shocks, you may consider using a 3 hole piston. However in some cases you may want the chassis to react slower, then a 2 hole or 1 hole piston may be fitted.
If you want to be more precise, you can change the diameter of the holes using a 1mm drill. By working out the flow velocity of water through the hole as a reference, you can modify the hole to get different reaction from the shock and by that you can get a basic feel on the shocks.
Fig. 2 Different number of holes on a shock piston or even a quick change version (blue)
It supports the load and preload on the shock while absorbing bumps on the track. By changing the springs according to different spring rates, it changes how hard the tires trying to cover the ground surface as stiffer springs grab more while softer springs feels more loose. Although there are many types of springs in the market that comes in different spring rates, it is easy to decide their stiffness by hand as this is the first thing you may want to modify or change in terms of suspension tuning. In addition, you may consider buying multiple different springs in order to fine tune your vehicles, increase the capability.
Fig. 3, 4 I always bring extra springs to suit different tracks I go
This component affects the most on how the wheels contact the ground so it is important to acquire the right one in order to gain the maximum steering performance. When you are trying to change the positions on the knuckles. It is recommended to start with the stock position on the user manual as it will be easier to have an initial feeling of the vehicle. By that, you can adjust the setting bit by bit until you get the perfect set up.
As the figures show below, there is a slight difference between the drift setup (left, centre) and the off-road setup (right), as the drift knuckles have more options for adjusting the caster and kingpin position. Since off-road vehicles need to be more beefy to take any extra impact so the there’s one position only, lacking flexibility to tune on.
Fig. 5, 6, 7 (from left to right) drift type, drift type, buggy type
You can see that the buggy knuckle is more beefy and doesn’t have much options to change the geometry.
The following will explain how the above factors can affect the performance of the vehicle. For easier understanding, I choose drift tuning to further evaluate how these components are important when you want your RC to go faster and more aggressive than others.
To master the suspension tuning on drift RCs, first you have to understand how the suspension should be like. In short, the basic setup for Rear Wheel Drive (RWD) drifting is to have a soft rear and a slightly stiffer front in order to let the front tires to grab the ground more often to lead the vehicle as the rear should be a bit less stiffer since too much grip will lead to an unstable handling, causing it to spin out easily.
This is the basic tuning method for everyone to change grip levels, the concept is that the more inclined the shock from the ground, the less grip you will have as the shock is not fully absorbing the force from the surface instead it is absorbing the side force acting on the chassis while drifting.
On the other hand, it is important to know the distance between the wheels and the shocks. Besides the shock angle, if the shock is closer to the wheels, the less bumps it will absorb because it is stiff so it would bounce a bit when driving on rough surface. Vice versa, the more the shock is away of the wheels the softer the chassis act since the shock move out of where the force happens. So if your car oversteering too much, as known as over-angling. You may want to soften the rear, either moving the shock away front the wheels or add more angle on the shock position.
To conclude for drift settings, depend on the track you are on, if you want more traction. You may want to either straighten the shock angle or move the shock towards the wheels to gain more grip, vise versa. And make sure to combine these two methods when in use in order to get a balance set up.
Fig. 8, 9 (left) stiff position and (right) soft position
Shock rebound could be an interesting topic to get in depth but I will try to further explain in simple words as there’s a lot to learn on this topic.
Basically, shock rebound means the speed rate of the shock shaft retrieving after compressing it with no spring load on it, simply to test it with your fingers applying force to the shaft and see if both the shaft is moving in the same speed as it will affect the overall performance in corners, making sure the shock will match the chassis .
A slow rebound is mainly use for smooth surface as the shock acts slower, reflecting that the body roll will be slow as well as making the vehicle stick to the ground more often since the reaction is slow, causing it to have grip for a longer time before the shock reacts.
A fast rebound means the shock reacts quickly, letting the wheels to grab the surface rapidly. This also means there’s addiction extension force on the shock body before the spring has been fitted to it. This setup benefits the chassis when the driver wants a more responsive handling since there’s less roll on the chassis means the car can do a drift transition easily.
Fig. 10, 11 (left) original length, (right) with rebound tuning
Camber means how incline the angle is that the tire is touching the surface for the front, it is a critical element to determine whether your RC is having enough traction. The concept is quite easy to understand, the more camber it has (negative camber, never have positive camber), the more grip you will get as it is extending the track width, it will be more controllable and less chance to understeer while drifting in corners. When you feel like there is not enough grip, you could try to increase the camber to gain more grip as the front tire will have a better contact to the ground during the drift.
For the rear tires, the more camber, the less forward grip you will get. Since camber is all about the contact surface between the tire and the ground.
Some people will prefer a less aggressive camber setup. That’s because it has a stiff shock to generate more grip and by use a less aggressive camber, the drift line must be very precise or else you may find the car acting weird.
Fig. 12 using a setup system to check the camber setup
Caster is a difficult topic to discuss because it needs your imagination to think about how the steering relate to the caster and the tire tread contact the ground. To firmly explain, it is representing how the top of the wheel hub is leaning either forwards (-) or backwards(+). In normal cases, caster will be positive to cause the steering to self-center, preventing the vehicle to spin out. This will give the driver more directional stability on the chassis means it can prevent too much oversteer (over-angling).
Negative caster is not recommended since it will reduce steering response and causing a sluggish steering which is not ideal for drift setups. So do not consider negative caster in any time for any vehicles.
Fig. 13, 14 (left) full lock with positive caster, (right) caster will help to self-center.
Fig. 15 Using a setup system and a straight object to check the caster (it is showing the chassis has +10 degrees of caster)
Wheel hub and rim offsets
Wheel hub and rim offsets are directly related to the grab (not grip) of the chassis. First, I would like to define the difference between grab and grip. In simple words, grab is where the wheel trying to gain horizontal force in order to move the vehicle, while grip is where he wheel tempt to gain vertical force to let the tire stick to the ground.
To know how much grab you have on the chassis, simply sum up the thickness of the hexagon wheel hub and the rim offset. By calculating these numbers, you will have an basic idea on the grab level. For drifting, it is usual to have a wider front total offset than the rear since more grab is needed to control the direction of the drift. For example, a standard Yokomo YD2 has a 7mm and 5mm hex wheel hub on the front and rear respectively. By having a set 7mm offset rims, the total offset will be 14mm and 12mm respectively. This is a standard format setup for a drift chassis. Although there could be exceptions on front offsets that are narrower than the rear, it is not common to use this setup unless the track layout has tight corner that fast transition is needed. Then the front offset maybe shorter the the rear.
Toe is an element that controls the ackerman of the steering how the vehicle handles on their limits. To explain what toe is briefly, it is how the wheels pointing out or in from the vehicle. Toe out (+) on the front will result on more steering but less stability on straight line as toe in (-) will result on more stable on straights but too steady on corners. The base setup on your drift chassis should have a toe out front and toe in rear. In most cases, +3~5 degrees of toe out is recommended on the front since RWD chassis need more steering angle to drift through the corner while -1~2 degrees of toe in on the rear to keep the vehicle stable. But these base setups may be vary due to different tracks so it is important to test out different settings, just need to remember never have a toe in front or toe out rear.
Speaking of fine adjustments, too much toe out at the front will result on having a slower speed on straights and oversteer (over angling). Making the vehicle even slower on corners as the vehicle is “crabbing” instead of drifting through the corner with an angle. On the other hand, too much toe in at the rear will cause the rear to be “too straight” and won’t let the rear to kick out easily since the toe affects the tire tread to go inward towards the chassis, making it too stable to drift.
Fig. 16 Using a setup system to find the toe. 7 degrees toe out in the photo
To sum up, having a good suspension setup is the initial step to get your RC running smoothly. In order to make sure all the settings are right, it is recommended to start with the factory settings since most of the companies have developed a setup which everyone can enjoy. By starting with the stock setup, following and consider the elements above to test out the sweet spot of your own setup and make sure you record it using a setting sheet where some will come with the user manual.
If you find yourself lost in these settings, it is fine to reset everything and do it again as this will take a long time. I own a Yokomo YD2 for three years and I just recently getting close to find a perfect setup. So be patient, it will come together and by the time you will enjoy the hobby even more as your effort has been paid off.
I am Kelvin Wong. I started playing RC since 2015 with a Tamiya M-05 as my first RC car. Then I start self-learning on tuning four-link suspension trophy trucks with an Axial Yeti Trophy Truck and I have certainly learned a lot from that chassis. Then, I bought two Tamiya TT02s, Traxxas XO-1, HPI WR8, and an MST FXX-D to see what path suits me the most
Edited by Carlos Santos, your webmaster
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