This theme is one of the most talked about in RWD RC Drift society. There is no 'right' answer as this is purely driver preference and the style the driver is after. I will cover the BASIC alignments for the front tire and it will be up to you to find what works best for you.
WHAT IS CAMBER?
Camber angle is the vertical alignment of the wheel relative to the driving surface. At the neutral steering position, the top of the tire should be leaning into the body, which is negative camber. The reference range of negative camber at the neutral steering position is around negative 4 to 8 degrees. I would recommend to set the default around negative 6 and adjust from there. You should have a camber gauge, that can measure from negative 10 to positive 10 degrees.
So what does camber actually do? When you roll a frisbee on the floor, the frisbee will roll in the direction it is leaning into. Negative camber will assist in stabilizing the chassis in the direction of the lean. For example if camber is zero at neutral, for the chassis to drive straight, it is mechanically less stable than having a negative camber. However, it is very important to have left and right exactly at the same camber, otherwise the chassis will be pulled to whichever that has less camber.
The other key element in RWD RC Drift is the front tire contact patch that is dictated by camber. Using the edge with less contact, or using the larger surface with more contact, on the leading and trailing tires. Typically, more negative camber will increase control, less negative camber will make the steering milder. However, this is relative to how the other alignment is set in combination with camber, and also the profile of your tire. Extreme camber 'oni-kyan' may look cool, but will not necessarily improve the drivability...so let's be practical!
HOW DO YOU ADJUST CAMBER?
Typical adjustment is using the turnbuckle or slide adjustment of the upper arm. I prefer adjusting the lower arms so the tire fitment to the body stays the same. Using the digital caliper to make sure the left and right is identical, is very critical. If you change camber, the steering linkage will also need to be adjusted for toe in and your ackerman.
WHAT IS CASTER?
Caster is the angle created by the steering pivot point or the king pin in the front to back direction of the chassis. This angle should be leaning towards the back of the chassis. Caster is like the steering fork of a bicycle, the more lean, the more stable it is, but also makes the steering sluggish, or unresponsive. The reference caster angle I would say is around positive 4 to 10 degrees, and would recommend to start from around positive 6 to 8 degrees. Caster can be measured by using a camber gauge to measure the side of the ball joints on upper and lower side of the front knuckle, however if you have different size ball joints or depending on the shape of the front knuckle, you may have to take an approximate reading.
Caster is closely related to camber. As you turn your steering, the camber throughout the steering will change relative to the caster setting.
Leading tire = Negative camber will be cancelled out by caster, eventually going zero camber, then positive camber depending on caster setup
Trailing tire = Camber will increase by caster, and can increase to extreme camber depending on caster setup
HOW DO YOU ADJUST CASTER?
Caster is adjusted by the front to back position of the front upper arm and/or the lower arm. The more you push the upper arm towards the back of the chassis will add positive caster, or bring the lower arm forward to add positive caster. You can use spacers or shims to do this, but note that adjusting the lower arm for caster will change the wheel base, so you may need to adjust the rear tire position to adjust for the wheel base when you make any significant caster adjustments. Once again, any caster adjustments will require the steering linkage to be checked and re-adjusted. It may change the full lock position if you have a knuckle stopper or possibly cause the linkage to rub against the wheels depending on how much adjustment you make.
TOE OUT?
You probably have seen many chassis with the front tires toed out. Front toe in RWD RC Drift has a different meaning than other RC categories. Toe is mainly used to set the ackerman, or change in ackerman throughout the steering. I will cover ackerman in the later bulletins, but for now, I would set the toe to either zero or slightly out, up to 2 deg or so. Extreme toe out may interfere with the ackerman. As you will have negative camber at neutral, a slight toe out will actually make the chassis more stable.
WHAT'S NEXT?
Camber and Caster are the two basic elements in front alignment in RWD RC Drift. I will move on to KPI (King Pin Inclination), Trail and Scrub in the next bulletin. For drivers that are new to RWD RC Drift, I would focus on dialing the camber and caster before you move on to the next steps. To many drivers, how the front tire 'looks' when drifting is part of the 'style', but to move on to advanced setups, increasing the mechanical stability with alignment is key in setting up the chassis, in combination with the gyro setup.
Happy drifting!
February 10, 2018 / Charlotte NC