INFORMATIONAL: Short Course Trucks, Understanding Camber, Wheelbase, and Rear Toe
So I’ve read a bunch of different thing that everybody posts in the forums here about short course trucks, a lot of which is really informative, it’s always nice to have other opinions, I just happened to read three really cool articles, I’m far from a no it all, but am very familiar around RC's, after reading these I wanted to share them with everyone, I picked up some very useful information and hope it’s useful to you as well. Some of you may have read this or already know this but for those who don’t or those who need a memory jog…… Here goes: ( pardon me if there are any typo’s )
ARTICLE 1 “Understanding Camber”
The camber angle of the tire influences the amount of cornering force that the tires can generate. Tuning your short course truck with camber can help fix handling issues, improve lateral grip and decrease lap times. This discussion will describe how to set the static camber and the camber gain to get the optimum performance from your tires.
WHAT IS CAMBER?
The camber of the tire is the angle of the tire relative to vertical when viewed from the front of the chassis. A tire has zero camber if it's straight up and down. The camber is negative when the top of the tire is tipped in towards the centerline of the chassis, and positive when the top of the tire is tipped out away from the chassis centerline. The camber angle can be measured with an aftermarket camber gauge and it's best to measure camber on a level surface for an accurate reading; however, a pit table will do in a pinch. Make sure the truck is ready to run except for the body, and turn on the car and radio to lock the steering at its center point. Drop the chassis from about 6 inches onto the level surface so that the chassis finds its neutral ride height. Then use the camber gauge to measure the angle, being careful to note whether the camber is positive or negative. If the camber needs to be adjusted, rotate your turnbuckle to change the angle. After the camber change, always drop the chassis again and re-measure the angle for consistent measurements.
SETTING UP FOR THE TURNS!
For most tracks and surface conditions, it is desirable to set up the truck with at least a small amount of negative camber on the front and rear, as this will help increase the lateral grip available for cornering. During a cornering maneuver, the outside tires are heavily loaded due to weight transfer, and they will be responsible for most of the total cornering force. By adding negative camber, the top of the outside tire will be pointed more toward the inside of the corner. This will generate more lateral force, and the truck will turn faster. It is generally better to have less rear camber then front camber to keep the truck stable and for good forward bite. However, track conditions or driver preference may warrant breaking this rule.
Static camber is important, but how the camber change in travel and when the chassis rolls it’s important to tune as well. The amount the camber changes in the travel and in roll depends on the front-view suspension geometry. If the upper link and the a-arm are the same length and parallel, there will be no camber change with travel. But the camber will change by the same angle that the chassis rolls. Parallel or near parallel suspension geometry is desirable for off-road applications because the vehicle will be less darty when landing jumps or when navigating bumps in the terrain. This setup is not ideal for maximum cornering performance because the outside tire will assume the maximum positive camber when the chassis is rolled over during cornering. This results in much lower cornering force. However, this setup is great for forward bite, because it allows the tires to stay flat on the road. Short course trucks roll a lot in the corners, so tuning your camber gain can yield a big payoff in cornering grip. When the A-arm and the upper link are not parallel, there will be less camber change with roll, and some camber change in travel. The lower A-arm pivot is fixed on most trucks, so the way to change your camber gain is by moving the inboard or the outboard pivot location of the upper link. Moving the inner pivot down or the outer pivot up will yield negative camber in bump, and less negative camber loss in roll. In most cases, this will improve cornering performance. Moving the inner pivot up or the outer pivot down from parallel will yield positive camber in travel and less camber loss in roll. Setting up the truck this way in the back will make a tuck more stable on throttle. Some trucks have pivot holes to shorten or lengthen the upper link. If you shorten the upper link, there will be more camber change in bump, and if you lengthen it there will be less camber change. After a change is made to the pivot location, reset the static camber so that the comparison is valid.
There are many different combinations of static camber and camber gain settings to run on a short course truck, and an entire test day could be devoted to trying different setups. In general, if the truck needs some more cornering performance, add some negative static camber, drop the inner pivot, raise the outer pivot, or shorten the link. If the track conditions are slick or more forward bite is necessary, try less static camber or make the upper links run parallel to the A-arm.