Suspension tuning is not an exact science, but it covers a lot of components and it is easy to overlook some settings. One of these overlooked settings is your RC car’s caster angle.
But what is this caster angle anyways? It actually refers to the angle between the center of the axle block’s lower pivot point in reference to the center of its upper pivot point. In simpler terms, caster is the angle of your kingpins or steering blocks when viewed from the side of your RC car. Your car may have a negative, positive or neutral caster angle. Getting the right angle will improve your RC car’s handling and, of course, improve its suspensions.
A neutral caster angle refers to the situation when the kingpins or steering blocks are perpendicular to the ground. A neutral caster is the base measurement from which the other two caster angles can be measured.
Negative caster is achieved when the upper pivot point is in front of the lower pivot point and it is sometimes referred to as a leading caster. Positive caster refers to the situation when the top pivot point is further back than the lower pivot points and it sometimes called trailing caster.
Caster is used to add or detract from your RC car’s directional stability and its setting depends on the method of drive your RC car has. This means that a front-wheel-drive RC car will have different settings from a rear-wheel-drive model. Increasing positive caster will slow down steering, but it will increase your RC car’s stability in handling corners and will improve self-centering. It is generally advisable to have a positive caster angle on your car because a negative angle will only make your RC car very difficult to drive and control in both straight lines and in corners.
What about a neutral caster angle? The upper and lower pivot points of your RC car will be aligned vertically, thus the forces that bear down on the car and wheel will have only one point of contact, which will be influenced by external forces. This means a neutral caster angle will make your car very unstable.
But let’s take a closer look at how positive caster can improve your RC car’s handling. Less positive caster improves off-power steering into the corners, but it will lower your car’s stability in straight-line courses. Respectively, a more positive caster can give your RC car less off-power steering in corners, but more stability in straight-line driving. You should remember that the same setting can have different effects in front-wheel drive and real wheel drive cars.
How do you adjust caster? The adjustment methods can differ from many models because many manufacturers keep adding or refining more method to adjust camber angles. On some models, you just have to add or remove shins from the upper and lower suspension arms. If you want a higher caster angle, you should move the top further to the read or move forward the bottom. Just keep in mind the fact that you should adjust both sides the same, otherwise your car will be impossible to drive.
Another way to adjust the caster angle on some models is by changing the front hub carriers and steering block because some have front carriers with different degrees of caster built into them.
You can actually if you have set your front camber angle correctly. You have to look at the wear of your tires. If the inside of your front tires is more worn than the outside, then you need more camber. But if the outside is more worn, then you need less camber. And because the caster is only a small part of your suspension tuning, you should remember that if you happen to change caster, you should also need to fine-tune other aspects of your suspension.