These adjustments are the ones that make the least amount of difference and take some experience to feel.  Even some of the latter Level 2 adjustments may not be felt immediately so if you could not see what difference an Upper Camber Link change made, you probably won’t notice any of the Level Three Adjustment Changes. 

Shock Position 

Some cars only offer one or two shock positions but many after market shock towers can increase the number of available shock positions.  Here, this optional front shock tower has 8 different shock positions available for the upper shock mounting position.  Not shown but also available are two more on the suspension arms for the lower shock mount.   (HPI 1/10th Scale RS4 Pro 2 with optional # 73006 Front Shock Tower Shown.)

What it does:  Like the Camber Link Roll Center adjustment, many cars allow you to change the angle of the shock.  By changing this angle you can make the shock feel a little stiffer (the shock angled in or “laying down” more) or a little softer (shock standing more upright) as the car rolls.  Note that this is a fine adjustment where changing the dampening or spring would make too big of a change.

How to change it:  It is very simple, all you need to do is change where the shock mounts to the shock tower in relation to the Lower Arm mounting position.

When to change it:  If you want a little more initial turn in but less steering in the middle of the turn, lay the front shock down more or stand the rear more upright.  If you want a little more on power steering, lay the rear shocks down more or stand the fronts more vertical.

Tips:  Putting the rear shocks too close to upright can cause the back tires to skip a bit going around turns.  Laying down all the shocks can slow the car down even though it feels like it has more bite.  The more prepared the track is, the more you can lay down your shocks.

Cost:  Free if your car has the optional mounting holes. 
 
 
 

Wheelbase
 

What it does:  More like what it is.  The wheelbase is the distance from the middle of the front axle to the middle of the rear axle.  The longer your wheelbase, the more stable the car will feel.  The shorter the wheelbase, the more agile your car will feel.  Note that not all cars have this adjustment.

How to change it:  Most cars use thin shims on the hinge pins to adjust wheelbase much the same way some cars adjust camber.  Moving the shim to the front of the hub will move the hub back, moving it to the rear of the hub will move the hub further forward.

When to change it:  If you are racing on a very tight and technical track, a short wheelbase will work better.  If the track is long, wide and has big, sweeping turns, a short wheelbase may feel too jittery or twitchy and hard to drive.  A longer wheelbase would be a better choice to stabilize the car.

Tips:  If the track has some wide sections and some tight sections, a wheelbase somewhere between long and short might be the best compromise.  Play with this one a bit until you are comfortable with it.

Cost:  Free but not available on all cars. 

Ackerman Link 

Notice the inside tire (left tire on the right side of the photo) is turned slightly further than the outside tire.  This is Ackerman angle. (HPI Pro 3 shown here.)

What it does:  When your car goes through a corner, the inside tire must travel a shorter distance in a tighter circle than the outside one.  To accomplish this, it must be turned tighter than the outside tire.  The Ackerman Link on a dual bell crank steering system (all of the HPI cars have this) accomplishes this.

How to change it:  The Ackerman link is just like the Upper Links and Steering links.  It uses a turnbuckle to lengthen or shorten the link.  Lengthening this link will shorten the difference between the steering angle between inside and outside tire making the car turn in more aggressively and better high speed steering but giving less low speed steering and less low traction steering.  Shortening this rod will increase the difference between the steering angle and make the steering feel more stable.  Better low speed and tight corner steering ability.

When to change it:  Almost never.  You can play with this adjustment and see if a slight change in length gives you better steering for your particular track.  Most racers except pro level drivers will leave this at factory settings.

Tips:  If you don’t have calipers, don’t change this link as you will not be able to record what it is set at.

Cost:  Free if the Ackerman Link is a turnbuckle.
 
 

 Body Aerodynamics

The Dodge Stratus on the left is probably the most popular body among racers.  The large front window and blunt nose give it good front down force while the low roofline allows for cleaner air to hit the large rear wing for good rear down force and a very balanced feel.  The Dodge Viper on the right has great rear down force from the large rear wing and a front window that is close to the middle of the body.  However, because of the location of the front windshield and the sloping nose, there is very little front down force making this car push in high-speed turns. (7416 HPI Dodge Stratus 200mm and 7418 HPI Dodge Viper 200mm shown.)

What it does:  When you corner at low speeds, the traction that your car has is determined by tires, springs, and all the other items we’ve covered.  However, on high-speed corners, the body itself will generate down force, which increases the amount of weight on the tires and has a dramatic affect on handling.  Most Touring Car tracks will not have many high speed corners and this is why most people will tell you that body selection is not that big of a handling factor.

How to change it:  There are only two ways to change the aerodynamics of car, either change the body, or add/remove material from the rear wing.

When to change it:  If your car wants to push going through a fast turn but is okay on slower speed turns, decrease the size of the rear wing or change to a body that will produce more front down force.  If the car wants to spin out in high speed corners but is fine everywhere else, then go with more rear wing or with a car with less front down force.

Tips:  With touring cars, the Dodge Stratus is regarded as the most well balanced body producing the most overall down force on the market today.  Some other bodies, such as the HPI Ford Mondeo, will fell just as balanced but produce less down force.  Others such as the HPI Alfa Romeo 256 will produce a lot of down force, but the one end of the car may have a little bit more down force than the other and the car will not feel as balanced.  The placement of the front windshield, the size of the front windshield, the shape of the nose, the height of the roof and the size and height of the rear wing all play a part in how well a body will handle aerodynamically.

Cost:  Free if you just modify the rear wing up to $40 for the cost of a new body.

One-ways

The picture on the left is a front one-way differential.  The picture on the right is a front one-way pulley.  One-way units will lock when turned in one direction but will spin when turned the opposite direction.  Each one has its own benefit but by using them together you can get the combined benefit of both units. (Pro 3 Front One-Way Differential and Pro 3 Front One-Way Pulley shown.)

What it does:  One-ways will make a huge difference on the way your car handles.  We recommend that you have a good feel for your car with standard pulleys and differentials installed before you try switching to one-ways.  There are two types of one-ways available and both work a little differently.  The first is a Front One-way Differential.  This one-way will allow the front tires to freewheel anytime the front wheels are moving faster than the rest of the drive train such as when braking or decelerating.  This will give the front tires more traction because they no longer have to work to slow the car down and 100% of their grip can be used for steering.  When you begin to accelerate out of the turn, the front tires will re-engage and help pull the car out of the corner.  If the inside tire begins to loose traction and slip, power will be diverted to the outside tire allowing for more steering out of corners.  With a standard front differential, if the inside tire were to slip power would be transferred to the slipping tire and on power steering would be lost.  The second type of one-way is the Front One-way Pulley.  This one-way replaces the small pulley that drives the front belt and front differential.  When the speed of the front tires is the same or faster than the rear, this one-way disengages the entire front drive train allowing the motor to drive just the rear wheels.  With the friction of the entire front drive train gone, the motor has to use less power to turn the drive train and will put more power to the ground.  This will increase run time because the motor will be more efficient.

How to change it:  To use a Front One-way Differential, you would just replace the entire front differential.  To use a Front One-way Pulley, you would just replace the stock front drive pulley.

When to change it:  Most people will tell you to run one-ways only on high bite tracks.  However, once you get comfortable using a one-way equipped car, you may never go back and some of the HPI drivers have raced successfully with one-way equipped cars on very dusty tracks.

Tips:  You can choose to run either one of the one-ways but most pro level drivers will run with both one-ways installed in their cars.  This way, you get the extra efficiency of the Front One-way Pulley and the increased steering of the Front One-way Differential.  When you change over to a one-way equipped car, no matter how many you install, take time to practice with the car.  The driving style required with these installed is very different.  You will have no front braking power and even taping the brakes can result in a spin.  The idea is to just ease out of the throttle but always have power going to the tires.  You should not have to reduce the throttle to neutral ever for stock and mod drivers should set up their brakes to be very light.  One-ways are not recommended for Nitro Cars as Nitro Cars do use brakes heavily.  If the car begins to spin out, resist the urge to back out of the throttle.  Doing so will only make the spin worse.  Increase the throttle and the car should straighten out.

Cost:  One-ways contain bearings and are made out of aluminum so expect the cost to be rather high.