TRC

Brushless Radio Controlled Cars

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RC Handling & Tuning Guide

Part 1   Part 2   Part 3

Caster Angle

The purpose of caster angle is basically to allow the front wheels to self-centre. Imagine the wheels on a good shopping trolley (if you can find one), if you look at the wheels the spindle of the wheel is not directly below the mount but trailed back at an angle, this is the caster angle. When you push the trolley the wheels all point in the direction of motion so are self-centred.

All rear wheel drive cars have positive caster on the front wheels.

Although the main reason for the caster angle is to self-centre the wheels the angle can affect the car handling as well. Too much caster and you can get what is known as wheel shimmy. This is when the front wheels flick side to side rapidly .Too little caster can make the car oversteer and be a little nervous. The caster angle is adjusted by sliding the front wishbones on the hinge pins. To increase caster slide the top wishbone back or the bottom one forward or a bit of both, and do the opposite to reduce the caster. It is very difficult to measure caster angle so it is more a case of trial and error to get the correct setting.

The best starting point would be both wishbones in the centre of the hinge pins as there is positive caster built into the steering hubs.

Torque RC .com 2011

Ride Height

Just a quick one on the car ride height. Try to run the car as low to the ground as you can without the chassis scraping the ground. Ride height is adjusted on the collars of the shocks, screw them down increases the ride height and visa-versa. Set the rear end a couple of millimetres higher than the front.

This is just the basic car set-up and will get your car round the track. Next we will go into more depth and detail about different changes.
If you wish to alter the settings only change one at a time to see if there is an improvement, don’t change two or three at a time as you will not know what has worked and what hasn’t.

Always remember, there is no such thing as a perfectly set up car. There is always a compromise, give to the front and you loose from the rear, give to the rear and you loose from the front.
 

Often overlooked and underestimated. The ride height of your car will determine a few things. Firstly and most importantly it will affect the centre of gravity of your car. The higher the ride height, the higher the centre of gravity. This will affect your cars ability to corner.

Let me explain: The centre of gravity of your car is basically where the centre mass of the car is, front to rear, side to side and height above the ground. All these factors will converge at one point on you car to determine the car’s centre of gravity. Apart from moving fuel tanks and battery packs we are limited to the amount of changes we can make to the linear centre of gravity. What we can do is affect the lateral centre of gravity.

When your car is travelling full speed up the straight it wants to keep travelling in a straight line. When we get to the end of the straight we want to turn the corner but the car still wants to keep going straight on. Now we have to think about leverage, the longer the lever, the more leverage. If your lever is 25mm long and you double it to 50mm then you double the amount of force applied. Now to apply it to the cars, if you run with 20mm ride height then drop to 10mm ride height you will have half the amount of force trying to push you in a straight line so it will let you turn the corner easier and quicker.

The front of the car should be a bit lower than the rear to allow for weight transfer during braking and cornering.

Run the minimum ride height that the track conditions will allow to prevent the chassis from Scraping the ground at every corner.

A good starting point for a touring car is front-6-10mm and 8-14mm rear.