In writing this, we set out to create a basic tuning guide for the community. We own vehicles that are highly tunable to suit numerous course conditions and driving styles. Why not take advantage of this? Because most of the time we don’t know where to start. Keep in mind that most tuning is to suit a drivers preference. Some like it twitchy, some like it smooth. What works for one, might not work for another. Tuning is a complex task, and when changing one thing, you often affect another. This setup guide was created as a quick reference, and runs on general cases. For more physics behind the setup, please check out http://home.scarlet.be/~be067749/58/. Please keep in mind this is a work in progress, and we’re not perfect. If you see an error, or would like to add to it, please PM us so that we may update the guide
While setting our cars up for drifting, we are looking for that perfect balance between slip and grip. We want our cars to drift through the corners, but we also want control of that drift. We tune grip in or out by changing the way the chassis transfers weight i.e more grip up front equates to more steering. This is the basis of chassis tuning. All adjustments require a properly working car that is properly set up. By properly working, we mean no bad bearings, nothing binding, etc. By properly setup, we mean droop is equal side to side (not necessarily front to back), ride height is equal side to side, camber is equal side to side, etc. Changes should be made one at a time so that any change can be noted. It is best to start with the kit setup and work from there. Believe it or not, RC companies do put R&D into this and provide the most beneficial all-around setup for kits.
Most chassis’ have aftermarket chassis’ in the form of graphite tubs, or two-deck carbon fiber chassis’. These chassis’ are stiffer than their OEM counterpart. Due to their stiffness, they are typically more sensitive to setup changes, and are more suited for high-grip surfaces i.e. carpet tracks where the increase in grip due to chassis flex is undesirable. The flex apparent in tub chassis’ provides more grip and is more beneficial for asphalt. The benefits of a flexible chassis has been noticed by top manufacturers, and incorporated into their carbon fiber chassis designs. Associated Electronics incorporated it into their TC4 and Hudy has incorporated this into their Xray cars, seen as Multi-Flex technology.
Chassis weight also plays a large role. Of course, electronics have a large role in this, but in general, tub chassis’ are heavier than their carbon fiber counterpart. Heavy cars will tend to be less twitchy, and less prone to being upset over bumps. That said, they will also be slower through transitions. Lighter chassis’ tend to hop and chatter more easily.
Things to adjust when your car is UNDERSTEERING (no particular order)
Things to adjust for OVERSTEER
Opposite of everything listed above!
HOW TO ADJUST SECTION
Always the first thing to look at. Even with a great setup, tires can ruin it. For competitions, tire choice is often controlled to level the playing field and make it more of a drivers competition. In general, radials (rubber tires) offer more grip, while plastics offer less.
Droop is often misunderstood and confused with downstop settings. Droop is the measure of travel of the chassis from its static position, to its most extended position (see Figure XX). The downstop setting alters how much downtravel you’re A-arms will experience. It is set by turning the screw in the A-arm (see Figure XXX). Therefore, altering ride-height and the downstops effect droop.
Adding droop on one end will increase grip on the other. So, if you are experiencing lots of off-throttle under-steer, you can increase your rear droop. Confused? As you let go of the throttle, weight shifts forward. By allowing the rear of the chassis to travel more upward (equates to more droop), you allow more weight to be transferred to the front tires, giving more steering. Droop can be a powerful setting, and if not properly set left to right (not necessarily front to back), you can end up with a chassis that does not handle equally left to right.
Caster describes the angle between the king pin and the vertical (see Figure XXX). It actually leans the tire in the direction of the turn. More caster will lean the tire more in the direction of the turn. This, along with camber effects the tires contact patch. Too much or too little lean will minimize or maximize the contact patch. However, in general, more caster will yield a smoother turning car, with less initial turn-in. Less caster will give you car with sharp turn in. This is why you see many off-road cars with caster angles of up to 25º. Less initial turn-in means less looping out on loose dirt. It is adjusted by changing out the C-hubs in the front (most likely have to be purchased separately).
See “Tires” section
Refers to the Ackerman angle, which is the angle difference between the wheels as they turn-in. The inner wheel will always have to turn in more than the outer wheel. As you turn in more and more, the difference between these two angles increase. This is usually adjusted on the steering turnbuckle connection on the front hub (see Figure XXX). A more angled connection will yield less Ackerman, and vice versa. For low grip conditions, it is generally recommended to more Ackerman
Refers to the width of the car, measured from the outside of each wheel (see Figure XXX). Wider is better, right? For stability, yes, sharp turn in, no. A narrow front track width will increase the front grip and steering. A narrow rear track width will increase steering on the front end at low speeds, and increase grip at the rear at high speeds.
Front one way vs. Ball Differential
There are various techniques which I have adopted for my style. First off, consider that I run a front one-way differential, and a very tight rear ball-diff. I would say that the output ratio is about 50:50.
I would first off say that when fully releasing the throttle at a general fast speed, a chassis equipped with a front one-way would induce the rear to swing out significantly during a steer in. The simultaneous actions of releasing the throttle (and allowing the rear to "lock up"), and steering into a turn, the initiation of the slide is apparent. This behavior is normal for cars equpped with front one ways. Some will agree that one-ways have an advantage for extremely complex technical tracks, especially with short S turns. Another advantage is that if needed to correct an angle assuming that you missed your ideal pivot line of a turn, a driver with a one-way can hit the brake to swing the rear out in order to correct an angle so that you can complete a hard corner rather than plowing into a wall. Although, initiating drifts by taking advantage with a one-way, if not perfected, choppy drifts may be the result. Car's with a front ball-diff tend to behave more fluent during drifts, but unfortunately suffer from understeer as compared to a car with a front one-way.
Other than inducing the drift by means of throttle off/braking drift with the front one-way, I usually power over into turns. This is my dominant technique for long sweepers of medium turns. During the mid drift, I pulse the throttle depending on how much I need to break the ABS from the surface or on how much I need to correct the angle. I will never completely release the throttle unless a critical angle correction is needed.
I think we all know that excessive counter steering should be used seldomly given that our 4wd drivetrain minimizes the necessity of extreme countersteer. I've noticed that most of us countersteer fully when they prevent themselves from spinning out during corners where the car untered beyond the ideal angle. Most times, drivers let the rear "steer itself".
Also check this post for more details into the theory of front one way vs. ball diff. Click here.