Dirt track chassis setup

Fuel mileage is another thing to keep track of. Knowing how many laps you can get on a fuel run will allow you to keep in the back of your mind, when you will be forced to pit. Can I make it on a full tank of fuel or will I need tires first. If so what lap will I have to pit should we go green the whole way. I also like to keep track of how the car reacts as tires wear, as well as how it performs with less fuel in the car.

How bad do lap times decrease over X number of laps. What chassis adjustments could I make during a pit stop to help counter react the way the chassis performs with less fuel. Perhaps a track bar or tire pressure adjustment would be the way to go when pitting after so many laps. All these types of questions I have answered before entering a race because of good note keeping.

Simply reading your setup notes will remind you once again what you can expect from the setup you will be running before even getting on the track. If you have multiple setups for various weather conditions reviewing these notes will allow you to choose what setup to run given the current track conditions.

This is where using the track notes section of the garage area comes in handy read the section on track notes. A shock controls the speed at which the spring moves. Shocks are a very easy issue to become confused about. At times, too much or too little of the same adjustment on the same shock can produce the same exact results in the chassis.

Such results end up in total confusion as which way is the right way to go with an adjustment. The most important thing to remember regarding shocks, is that the stiffer the shock, the less grip it will have at the corner or end of the chassis. Shocks do NOT control the amount of weight transfer in a corner.

They will however control how quickly the weight is transferred. Shocks used on WC teams are rated from 1 through 9. The compression of a shock is when it is being pressed down.

The rebound is when it is being pulled back up. This means that the shock when compressed, has the same resistance when pulled apart. This shock would be stiff to compress, but would rebound or pull apart real easy. By adjusting the valving of each shock you can fine tune your chassis through a corner. When discussing shock tuning in depth, a basic understanding of dynamic weight transfer and its effect on tire loadings is necessary. Dynamic weight transfer is the transferring of weight from side to side during cornering, from rear to front during deceleration and from front to rear during acceleration.

The distribution of weight that transfers is affected by the rates of the springs used in the chassis. Basically, if one of a pair of springs receiving weight is stiffer than the other, the stiff spring receives proportionately more weight than the soft spring.

In rebound, a stiff shock slows down and a soft shock speeds up the unloading process. In compression, a stiff shock slows down and a soft shock speeds up the loading process. However, excessively soft or stiff shocks can produce effects opposite to those stated. Consequently, by changing the stiffness of the shocks used on a race car, we are adjusting the loadings on the tires at different points on the race track. If done correctly, good handling will result. The easiest way for me to explain when a shock is doing it's most work, is by using an ordinary automobile as an example.

Imagine a vehicle going down the highway at 50mph. Now imagine this vehicle slamming on it's brakes. What occurs in the chassis? What are the shocks going through in this state? Generally speaking, this is the exact same thing that occurs in a racecar upon entering the corner. Giving the car full throttle what occurs? Just the opposite of what was explained above. The front of the car lifts while the rear of the car squats.

The shocks on a race car are going to react the same way in the middle of a corner when your chassis takes set to full throttle. The balance of traction between the left side and right side tires determines to a great extent how the car will handle while decelerating through the corner. For example, a race car will tend to push whenever the left side tires do not have enough influence in stopping the car the right side tires are slowing the vehicle more than the left so the vehicle tends to go to the right.

Consequently, the left side tires remain loaded further into the corner which helps to turn the chassis. Asymmetrically changing the front or rear shocks can also give different results on the handling of a chassis. Decreasing the rebound on both front shocks allows the weight to transfer quicker from the front to the rear under acceleration. This will loosen a chassis more as throttle is applied. Increasing the rebound would produce just the opposite effects.

Asymmetrically adjusting the rear shocks will also produce different effects as compared to adjusting individual corners. If you understand springs read the spring section you will have a better understanding of how shocks operate. All of the asymmetrical theories that apply to springs also apply to shocks in much of the same manner. In other words a stiffer RF shock will tighten a chassis much the same as a stiffer RF spring will, albeit to a much lesser degree. To begin with your not always going to feel a major change.

Shocks adjustments are a fine tuning device only to be used after the rest of the chassis is close to being neutral or stable. Say 9 compression 9 rebound, or 1 compression 1 rebound.

Once again I bring up stiffer equals less grip on that corner. The reason many drivers do not feel a shock change is because they quickly forget the stiffer shock or shocks produce the least amount of grip. The RF is still stiffer. With a better understanding, you will have a much easier time deciding which shock to adjust to help cure or smooth your corner transitioning problem properly.

What works with one driver, might not necessarily be correct for another. This is due to the fact that different drivers have different driving techniques.

Smooth throttle, brake and steering transitions will require slower shock travel because weight isn't being transferred as quickly compared to those drivers that use abrupt throttle, brake, and steering transitions. Take for example a coil over shock that has a threaded collar for supporting the spring. If the collar has been turned up a number of times so the spring is compressed even when the shock is fully extended then the spring would be preloaded. In other words there is a load on the spring before there is any shock compression.

On the whole car, due to spring placement, suspension positioning, and tire diameters, etc. Adjustments in or out on the weight jack screws is the most common way the preload is changed.

Below is a general guide that should assist you in fine tuning your shocks. The stiffer the REAR shocks, higher the number the looser the car will be under acceleration. The softer the REAR shocks, lower the number the tighter the car will be under acceleration. The stiffer the REAR shocks, higher the number the looser the car will be under braking. The softer the REAR shocks, lower the number the tighter the car will be under braking.

Shock synopsis: RF Higher compression will tighten the chassis entering a corner. Lower compression will loosen the chassis entering a corner. Higher rebound will tighten the chassis accelerating out of a corner. Lower rebound will loosen the chassis accelerating out of a corner. Overall stiffer RF shock will tighten chassis, weaker will loosen it. RR Higher compression will loosen the chassis accelerating out of a corner. Lower compression will tighten the chassis accelerating out of a corner.

Higher rebound will loosen the chassis entering a corner. Lower rebound will tighten the chassis entering a corner. Overall stiffer RR shock will loosen chassis, weaker will tighten it. LF Higher compression will tighten the chassis entering a corner. Overall stiffer LF shock will loosen chassis, weaker will tighten it.

LR Higher compression will loosen the chassis accelerating out of a corner. Overall stiffer LR shock will tighten chassis, weaker will loosen it. Asymmetrical changes: The stiffer the shock, the less grip that tire will have. Stiffer rebound on the left shocks will help the car turn in by slowing weight transfer to the right.

Stiffer compression on the right shocks will help the car turn in by also slowing weight transfer to the right. Softer rebound on the front shocks will loosen the chassis exiting the corner. Softer compression on the rear shocks will tighten the chassis exiting the corner. Doing just the opposite mentioned above, on either compression or rebound will produce just the opposite results. Asymmetrical changes seem to have a greater influence than individual shock changes.

General: Use the above info as a guideline only. Changing just one shock may not give you the exact results mentioned above. Other factors must be considered. The spoiler itself is a wide piece of rigid aluminum located on the rear deck lid that spans the length of the trunk. The purpose of a spoiler is to add down force to the rear of the car. This is accomplished by how the air is passed over the back of the trunk lid as it hits the spoiler.

The same basic theories that apply to an airplane wing apply to a spoiler on a race car. When an airplane takes off from a runway, you'll notice that the rear flaps on the wings point downward.

This is actually just the opposite of how a spoiler works on a WC race car. When the flaps are pointed down on an airplane it assists the plane is lifting up to get off the ground. This isn't an effect you would want in a race car. This is the effect we desire at most race tracks. The rear spoiler catches air pushing down on the back of the car allowing for better traction through the corners.

How much air catches the spoiler is determined by what angle the spoiler is placed at and the rake of the chassis based on ride height. The lower the number the straighter the spoiler or the less down force there will be on the rear of the car.

You may think a setting of 70 would be the best for cornering, and it might very well be depending on the track. The disadvantage to running a higher spoiler angle is that it increases drag slowing you down on a straightaway. Picture yourself holding your hand out the window of an automobile traveling 55 mph, with your palm facing down towards the road.

You'll notice how the wind pushes your hand back a little bit. This would be similar to a spoiler angle of 45 degrees in a race car. You'll notice how much stronger the wind appears to be pushing your hand when you rotate it. This would be similar to you running an angle of 70 degrees on your rear spoiler. Obviously the force on a rear spoiler going mph over the length of the rear deck lid will be a lot higher than your hand out a window.

On a high banked high speed track like Talladega, you'll probably want to run the minimum spoiler angle since down force isn't as critical. A track like Talladega naturally creates down force on the car. The majority of other tracks will require higher degrees of spoiler to keep the rear end glued to the track. To keep it simple, the higher the spoiler angle the tighter the rear will be.

The lower the angle the looser the rear will be. Spoiler synopsis: The higher the angle the slower your straight-away speeds.

The lower the angle the faster your straight-away speeds. The lower the angle the looser the chassis. The higher the angle the tighter the chassis.

Springs Four coil springs are located at each corner of the chassis. The springs determine how much weight is transferred to each corner of the car. The springs are mounted in such a way that they can be adjusted up or down to change ride heights.

Springs are rated by how many pounds it takes to compress the spring 1". This is done using a special tool called a spring compressor. The ideal spring combination is one that would produce equal amounts of wheel travel at all four corners of the car. At all ovals, the heaviest weight is being transferred towards the RF upon entry into a corner. This means the RF corner of the car will travel more requiring a stiffer spring than the other 3 corners.

The higher the numbers the stiffer the spring. The front springs are adjustable in 50 lb. The rear springs can be adjusted as low as lbs. An overall softer spring package is usually preferred over a stiffer setup. With a softer setup though, you run the risk of having the car bottom out on the track. Using softer springs will cause the car to roll over more in the corners.

This may require using higher camber angles to compensate for the roll. In general stiffer front springs will make the car tighter. Stiffer rear springs will loosen the car. Running more spring stagger up front, with a weaker left side spring, will tighten the car under acceleration while loosening it under braking. The greater the difference, the greater the chassis response during these transitions.

Running more spring stagger in the rear, with a weaker left side spring, will have just the opposite effect as the front. A stiffer RF spring will make the car tighter. A stiffer LR spring will tighten the car from the middle, out of a corner because it keeps cross weight in the car.

You'll notice that when making a spring change either stiffer or weaker, it will have the same effect on the chassis as it's diagonal opposite corner. In other words, if you decide to make the RF spring weaker to help loosen the car, you could also make the diagonal opposite corner LR weaker to also help loosen the car. In all actuality, what your doing by changing both diagonal corners together, is changing the wedge or cross weight of the chassis.

Try to remember the diagonal corners as pairs. And that whatever one pair does, the opposite pair will have the opposite effect. Using this method makes remembering what spring does what a little easier. In reality then, all you have to remember is what one spring adjustment does, and you should remember how all the others corners are effected. Let me give you an example. Just remember that a stiffer RF spring equals a tighter condition.

Now I know that diagonally a stiffer LR spring also equals a tighter condition. All will help to tighten the chassis. I remember all this by simply knowing that a stiffer RF spring equals a tighter race car. Let's try to put it in it's simplest form. Spring synopsis: Weaker LF will make the car tight. Weaker RR will make the car tight. Weaker RF will make the car loose. Weaker LR will make the car loose. Stiffer RF will make the car tight.

Stiffer LR will make the car tight. Stiffer LF will make the car loose. Stiffer RR will make the car loose. Overall stiffer front springs will make the car tight. Overall stiffer back springs will make the car loose.

Overall weaker front springs will make the car loose. Overall weaker back springs will make the car tight. Steering ratio is measured by dividing the number of degrees the tire is turned into the number of degrees the steering wheel is turned.

The lower the ratio the quicker the steering response. You'll notice that using a lower steering ratio will require less turning of the wheel to negotiate a corner. This low steering ratio can result in a twitchy car since the smallest of steering inputs will be felt in the car. It is very easy to over steer a car with such a low steering ratio. A car with a higher steering ratio will require more steering input to get through a corner. Too high a steering ratio might give the feeling of a tight race car as you find yourself turning the wheel further to negotiate a turn.

This isn't a push, it's just requiring more movement in the wheel to steer the front tires the same amount as with a lower ratio.

With a ratio of at a track like Michigan you might only have to turn the steering wheel 45 degrees to the left to get through the corner. With the same exact setup, but a ratio of you might have to turn the wheel 90 degrees or more to the left to negotiate the same exact corner.

There is no correct setting for steering ratio. A lot of this depends on the type of steering device used. With so many different wheels on the market, you wont know what is comfortable for you until you experiment with it yourself.

You may be comfortable with a steering ratio of at Dover with a TSW brand wheel, but find that after using a MadCatz wheel that the ratio is all wrong. This is because some wheels turn more or less degrees than others requiring different steering ratio settings.

Road courses are a track with slow sharp turns that would require a lower ratio. High speed long sweeping corners would not require such a low steering ratio since you are not required to turn as sharply on tracks like these. Steering Ratio synopsis: The lower the ratio the quicker the steering response. The higher the ratio the slower the steering response. Lower ratios require less turning of the wheel to negotiate a corner. Higher ratios require more turning of the wheel to negotiate a corner.

Tire Pressure Tires are the most important component on a race car. In fact, every single thing you adjust on a race car is for the benefit of the tires. All these adjustments that I've discussed in this guide are all about trying to achieve the best possible grip from the tires to the track. If you have the best grip at all 4 wheels, then you'll have the fastest car on the track.

Tire pressure is yet another adjustment that will aid you in achieving the best possible grip. Tire pressure is simply how much air you have in a tire.

The hotter tires get, the more they expand. Air contains moisture. WC teams actually don't use air in their tires they use nitrogen. Nitrogen is preferred over air because it doesn't expand as much with temperature changes because it doesn't contain moisture. Since it's impossible to remove all the moisture from a tire, it will still change pressure as temperatures rises. When tires expand it changes the size of the tire which in turn changes the weight on that wheel.

This can be either a negative or positive situation depending on your chassis needs. Tire pressures can be adjusted on all 4 tires from as low as 8 psi. Improper tire pressure can cause an ill handling car. Correct tire pressure can be determined by reading tire temperatures. A tire with a temperature reading higher in the center of a tire indicates an over inflated tire. Over inflated tires will have a tendency to make the car tight.

Under inflation can slightly loosen a chassis but give better grip. Lower tire pressure will also increase the amount of heat in that tire. Excessively low tire pressure produces more heat which can result in quicker wear.

Altering tire pressures allows us to slightly modify the stagger. Stagger is the circumference of the right side tires compared to the left side tires. The best way I can describe stagger is by using a white Styrofoam coffee cup. You know, the kind that is bigger around on the top than on the bottom. Now push it along the table letting it roll. You see how it turns in one direction. This is stagger. Imagine the top or larger side of the cup as the right side tires on a race car.

Imagine the bottom or smaller side of the cup as the left side tires. See how it turns left? Stagger on a race car works the same exact way. By increasing tire pressure on the right side, or decreasing pressure on the left we add stagger to the chassis allowing the car to turn left better through a corner especially under acceleration.

One thing to keep in mind when dealing with tire pressures, is that your also changing the weight of the car on the corner your lowering or raising pressure at. By raising or lowering pressure your changing the ride height of the chassis.

Changing the ride height adds or subtracts weight from that corner of the chassis. So tire pressure actually reacts like a spring. Adding more tire pressure makes that corner of the chassis a little stiffer. Lowering tire pressure will tend to make that corner of the car softer. Tire psi synopsis: Higher psi in RF will loosen the car. Lower psi in the RF will tighten the car. Higher psi in RR will loosen the car.

Lower psi in the RR will tighten the car. Higher psi in the LR will tighten the car from the middle out. Lower psi in the LR will loosen the car from the middle out. Higher psi in the LF will tighten the car. Lower psi in the LF will loosen the car. The lower the psi in a tire the hotter it will run. The higher the psi in a tire the colder it will run. Excessively low front tire psi will create a push. Excessively low rear tire psi will create a loose condition.

Increasing the split more RR psi than LR increases stagger, helping the car to turn in the middle of a corner. Tire pressure allows us to fine tune the chassis. Drastic pressures changes at various corners of the chassis could produce less than desirable results. Keep an eye on tire temperatures. Although your changing the weight on each tire with tire pressure, your changing it to a much lesser degree than with a spring change.

Tire Temperatures When I talk about the inside of each tire, I'm referring to the edge closest to the brake rotors or inside of the car. When I refer to the outside edge of each tire, I'm referring to those edges that are furthest from the brake rotors. I previously mentioned that every adjustment we attempt to make on a racecar, is an attempt to try an maximize the grip of each tire. By taking tire temperatures of each tire we can "read" how well our chassis is performing.

Tire temperatures are the only scientific proof we have of how a chassis is working. It's easy for a driver to misinterpret how a car is handling. Tire temperatures eliminate that mystery by telling us which corner of the car is over or under worked. The information I am going to discuss below, is what I've learned over the years working on real race cars. Some of the tire testing information I will mention below has given me various results within the sim. Some of this information transfers over to the sim rather well.

Use this information to the best of your advantage to better understand the concept behind reading tire temperatures. Tire temperatures are taken with a tool called a tire pyrometer. By comparing tire temperatures across the surface of the front tires we are able to tell if we have proper camber angles, proper toe, proper weight distribution, as well as proper tire inflation.

Comparing diagonal averages indicate the proper amount of wedge in the chassis. The optimal tire temperatures should be in a range of to degrees. Keep in mind that the hotter the tire the quicker it will wear out. The inside of each tire is the edge closest to the brake rotors or inside of the car. The outside edge of each tire are those edges that are furthest from the brake rotors.

This is because of the way the tires travel down the straightaway. On a larger track with longer straights, this spread will be even further. On an oval, the RF tire will have more negative camber, thus resulting in the inside edge of the tire contacting the track more than the outside edge giving you the higher temperature.

On the LF you will run with more positive camber, so just the opposite holds true. The more camber you run, the higher these spreads will be. On a small track were you spend a lot of time cornering, you'll find the spread not as high. This is because your spending more time cornering than on the straights, thus distributing the temperatures across the face of the tire more evenly. If you try to achieve even temps across the tire you may develop a push.

This is telling you that you have too much positive camber. Although the tire may be flat on the track, on a straightaway, the tire will not be flat on the track while cornering. By comparing the average temperature of all four tires you can see which corner of the chassis is working harder than the other. If your RF is a lot hotter than the other three tires your probably pushing because the RF is doing too much work. Work on cooling that tire off by lowering the RF spring and allowing the other tires to share some of the work load.

By comparing the RF average to the RR average you can tell if the chassis is loose or tight. The RF should be about 10 degrees hotter than the RR. If it's higher your probably pushing. If it's lower your loose. A tire is being under worked when it's temperature is a lot lower than the other three tires. When a tire is cooler or under worked, try concentrating on that corner of the car.

Try adding weight to that corner of the car to increase the temperature of that tire. If a tire is a lot hotter than the other 3 work on making that tire cooler. If it is warmer you have too much cross weight.

If it's cooler then you need more cross weight or wedge. Don't expect to learn everything reading the temps only once. It will take a number of 10 lap sessions to sort everything out that is going on with the tires. When analyzing tire temperatures it should be done in a specific order. This is because a problem in one area may mask a problem in another area.

Here is what I do. Run 10 laps, adjust front cambers. Run another 10 laps. Adjust tire psi. Run 10 laps. Adjust toe if needed. Adjust wedge. Run 10 laps.. Look for overheated or overworked tire. Adjust on that corner. Repeat the process all over again. Run 10 more laps. When checking tire temperatures it is important to make sure your not locking up the brakes or making any sudden changes in your steering outputs.

These will all create erroneous tire temperatures readings. Let me try to simplify how to read tire temperatures by giving you this guideline. Let me reiterate once again that the results you see may vary. Lets look at a few examples. Overall average temp is The RR is approximately 26 degrees hotter than the RF. If this RR is also the hottest tire on the car, it indicates the RR is doing the majority of the work in the corners.

This is the corner of the chassis I would work on. We need to take some weight of this corner to cool this tire. I'd start by going with a weaker RR spring. Average temp. Let's compare this with the RR below taken on the same car.

This tire is 10 degrees cooler than the RF indicating a neutral handling chassis. This should be good, but we could be faster with a camber change on the RF. The average temp is After the camber adjustment we no longer have a neutral handling car, but one that is now on the verge of becoming loose.

Your general feeling may be that the camber change made the handling worse, and it very well may of. But were still heading in the proper direction. You may have to take a step backwards at 1st to take 2 steps forward later. To increase the heat in the RF try a stiffer spring. To decrease the heat in the RR try a weaker spring. Either way you will make the car tighter. How much of a change depends on how much it changes your tire temps. Bob also had several of the top regional drivers piloting his personal race cars through the years, racking up an impressive list of wins.

In , Bob's only son Mark, followed in his fathers footsteps and started working in the chassis shop when not at school or work. Already a highly qualified crew guy on the legendary 21 late model s and modified s to come out of the TRC stables, Mark quickly mastered the craft of fabrication. Before long, Mark would take over the primary fabrication duties at TRC and build the company into the one stop shop for chassis, parts and service.

Under the direction of Mark and the watchful eye of Bob TRC has the solutions you need to get on the track and into victory lane. The quality and integrity that goes into these cars are second to none.

All the employees at TRC are racers themselves and know what it takes to build the highest quality product. If it races on dirt, we can fix or service it. Scott Sweeney Jr. Meanwhile, Chad Homan and Doug Surra both doubled down with wins. Homan Adds Win No. He took his Lazer Chassis No. Lazer Chassis Clients, please remember to send us your accomplishments to be included on the site.

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