INFORMATIONAL: Short Course Trucks, Understanding Camber, Wheelbase, and Rear Toe

[im2lo4ya]

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.

PART 1
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.

PART 2
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.

PART 3
CHASSIS ROLL!
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.

PART 4
WRAP UP
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.

[im2lo4ya]

Article 2 “Understanding Wheelbase”

Wheelbase has profound implications in the term of vehicle handling. It dictates much how well the truck will accelerate and turn, and it can be changed to suit a particular driver and track conditions. Here’s how to tune the wheelbase so you can optimize it for your track and driving style.

PART 1
WHAT IS WHEELBASE?
The wheelbase is the distance between the center of the contact patch of the front tire and the center of the contact patch of the rear tire. This is easy to measure on an RC car with a tape measure or machinist’s ruler. To get an accurate measurement, make sure to turn on your car and radio so that the steering servo is centered at your normal trim position. Having your ride height set properly also aid in giving you an accurate measurement of wheelbase. On most RC cars, wheelbase changes are made by moving shims on the outboard pivots of the A-arms. Thus, it is less important to know the specific measurement than it is to know how the shims are arranged if you are keeping track of it on a setup sheet.

PART 2
IN THE TURNS!
The cornering performance of a car is dictated in large part by the wheelbase length. A car with a longer wheelbase will be more resistant to rotating through a corner, while a car with a short wheelbase will rotate faster in a corner. On a tight track or a track with a lot of grip, it may be advantageous to run a shorter wheelbase to get the truck to rotate better in the center of the corner. On a long track with mostly wide corners or a slick track, lengthening the wheelbase will keep the truck stable so you can use more throttle for faster cornering speed.

PART 3
OVER THE BUMPS!
Loose or tight handling issues like this can be addressed by changing the wheelbase at just one end of your short course truck. If you move the shims to make the wheelbase longer at the rear of the truck, the static weight on the tires ( if measured with scales ) gets heavier at the front which will make the truck feel tighter. The opposite is also true. If you’re consistently fighting a specific handling condition, it is worth trying to change it during your race preparation at home.

PART 4
FORWARD BITE!
Wheelbase changes can also be made to affect the forward bite. On a 2WD truck, shortening the wheelbase will help transfer more weight to the rear tires under acceleration. His will help the rear tires dig into the track and also help with forward bite. On a 4WD truck, the answer is not as obvious. Since all four tire are being used to accelerate a 4WD truck, more weight transfer to the rear of the truck will serve only to make the front tires less effective. Lengthening the wheelbase on a WD will keep he tires loaded more evenly during acceleration which will help overall acceleration. It will also be more stable on corner exit with the front tires doing more of acceleration work.

PART 5
WRAP UP
Changing the wheelbase is another tool to make the truck handle and accelerate better. Build your kit with the stock wheelbase option, but make some changes during practice sessions to see if you can get a handling and acceleration characteristic that better suits your track and driving style.

[im2lo4ya]

Article 3 “Understanding Rear Toe”

An important tuning parameter for good cornering stability is rear toe. The correct rear toe setting will allow for fast cornering, confident throttle application, and better lap times. Take a look and see what tuning your short course truck rear toe can do for you.

PART 1
WHAT IS REAR TOE?
The rear toe is the angle of the rear tires relative to the centerline of the chassis when looking down at the top of the vehicle. Toe-in is when the front of the tires are pointed towards the chassis and toe-out is when the fronts of the tires are pointed away from the chassis. The stock setup for most trucks will have a degree r two of toe-in, and even this small angle should be perceptible if the rear tires are on the truck. The rear toe in a short course truck is set by the angle of the pivot holes in the rear pivot block, or by the angle of the hole in the rear bearing carrier. The normal adjustment range is usually from zero to three degrees, although it depends on what aftermarket components are available for a given truck. Consider the orientation of the pivots and carriers during your chassis build, as installing them backwards might induce disastrous handling effects.

PART 2
IN THE TURNS!
Rear toe-in will make the truck more stable throughout a corner. This is because the outside rear tire is artificially steering the truck away from the center of the corner. For example, in a left-hand turn, the front tires are both turned left to steer the truck though the corner. He right rear tire will be pointed to the left too, but since the tires are behind the center of rotation of the truck, it will actually be trying to steer the truck to the right. However, the left rear is more lightly loaded the right rear and will not be contributing as much cornering force to the maneuver. Therefore, the artificial rear steer angle of the outside rear tire is resisting steering input and making the truck more stable.

PART 3
STRAIGHTAWAY STABILITY!
Toe-in at the rear will also make the truck more stable on a straightaway. If the truck hits a small bump in the track or one of the tires gets into some loose dirt, the truck may start to rotate. However, thetoe-in at the rear will be resisting the rotation of the chassis and will keep the truck going straight without having to counter-steer as much.

PART 4
DIAL IT IN!
It’s best to run as little rear toe as can be tolerated for a given driver and track conditions. A truck will turn faster with a minimum amount of toe-in, because the rear tires will be helping to turn the car instead of fighting the corner. On a high-grip surface, start with zero of one degree toe-in. Assess if you have enough stability to run consistent lap times, and if there are no problems with being too loose; try to go down another degree. If he track conditions are prime, it might even be possible to run a small amount of toe-out. In contrast, if you have a low-grip surface or are new to racing, start with at least two degrees of toe-in. This will help make the truck more drivable, and adjustments can be made from there depending on how edgy the truck feels.

PART 5
WRAP UP!
Rear toe adjustments can be made useful when tuning your truck to track condition. Try to run the least amount of toe in the rear to find the best balance between cornering speed and chassis stability.

[batman]

the science behind the vehicle is always helpfull
thanks for the great post

[WhiteTech]

Indeed, very very helpful. Although I'd put it under general RC chat. Not exactly short course specific

[ian2]

well it is more of a short course SCIENCE because i do not no of any monster trucks or boats or anything with camber and toe, wheelbase ! anyways great post

[SportFury]

well it is more of a short course SCIENCE because i do not no of any monster trucks or boats or anything with camber and toe, wheelbase ! anyways great post

While I do kinda agree, this is more for SC trucks but can be used w/ most "race kits".

You can adjust camber/toe on some monster trucks, most people don't. My Savy is set up to adjust

[im2lo4ya]

yeah theres a couple more articles about short course trucks i want to share with everyone, ive been in debate about getting one, still torn between 2wd or 4x4 though, but after reading this magazine totally about short course truck i am now sold on getting one. i will type then up this weekend sometime and post them.

[MERVlife]

gr8 advice im2lo4ya! if your debating 2x4 or 4x4, 2wd will make you a better driver, 4 wheel drive can go more places, but there are more parts involved which usually equals more maintenance.

I've owned a Slash 4x4 and a few 2wd trucks and I will say the 4x4 handled quite a bit better. It was much easier to accelerate through corners and keep the truck straight. Plus it NEVER got stuck if I somehow ended up off the track.