Bristol chassis setup

I run the Back of the Pack league and we are running Late Models. Think of it as a safe haven training ground. We have about 50 members, but around 22 active every week.

We race the iRacing track one week before they do to prepare like your league. It has actually resulted in official wins for some of our drivers. You should come by sometimes and give us a setup class….. Thanks again for everything. The best setup class I found was the Gary Hensley setup videos in the iRacing forum or in the help section on this site.

I did take it pretty easy in the race and it was perfect all the way to the end and I got the win! Thanks so much for all you do! Hi guys. Drebin Dirt. Eldora Dirt. Jefferson Dirt. Las Vegas. Mid Ohio. New Hampshire. Richmond Dirt. Road America. Taggert Dirt. Texas Dirt. Watkins Glen. Es wurde ein Browserfehler festgestellt. 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. Eventually you should be faster than your neutral handling setup with improper camber in the RF.

As you can see from the above example there isn't always an immediate cure. Chassis setup is sort of like solving a puzzle. Always keep in mind that you may be going the correct way, but there could be an adjustment elsewhere that may be masking your initial change.

Because of this chassis setup can become very frustrating for the novice and experienced alike. For every change you believe your making for the better, it will have an adverse effect elsewhere in the chassis. Curing the loose condition exiting the corner now has probably messed up your chassis going into the turn. Now you must loosen it up again. Tire Temperature synopsis: Optimal temp range is between degrees. The hotter the tire the quicker it will wear.

The hottest tire on the car is the tire that is being worked the most. The coolest tire is the least worked. Work on the corner of the chassis that is either the most overworked or least worked 1st. Track Bar The track bar or panhard bar as I like to call it, is simply a bar that is mounted behind the rear-end that keeps the rear end from moving from side to side while cornering. The left side of this bar is mounted to the rear-end, while the right side is mounted to the frame.

Rear roll center directly effects the body roll experienced in the car. Within the sim we are allowed to lower the bar as low as 7. This measurement in inches is simply telling you how far off the ground the track bar is located. Adding stagger to the track bar changes the angle at which the bar is mounted. By changing the track bar from level, to either uphill or downhill raising or lower only one side, the LR or RR you add rear steer to the car.

The easiest way to describe rear steer is by equating it with wheel base. If one side of your wheel base measurement is NOT the same as the other, you have rear steer. When you add rear steer to the car by running track bar stagger, you change how the chassis will perform at various points throughout a corner.

Raising the right side of the track bar, or lowering the left side, will make the car looser under acceleration while at the same time tighten you up under braking. How much tighter or looser? It depends on how much track bar stagger you have.

Track Bar synopsis: Raising the bar on both ends loosens the chassis. Lowering the bar on both ends tightens the chassis. If you haven't yet read the setup notes section please do so now. Proper note taking is the most overlooked aspect of chassis setup. You can never have too many notes. Without proper note taking your always trying to find a needle in a haystack. With proper note taking you will at least know in which part of the haystack to begin your search.

Was it clear or cloudy when you tested with this setup? What was the temperature? What happens to the chassis under different weather conditions? I'll also keep track of how I like to enter or exit the corners with the current setup.

What is the best line around the track to take with the current setup? Enter a race informed of the situation at hand. Proper note taking will keep you one step ahead of the competition. Transmission Ratios The transmission is designed to change the high rotational speed and low torque turning force of the engine's crankshaft into the higher-torque rotation needed to turn the wheels over a range of speeds.

Transmission ratios vary through the 4 gears selected during shifting and are adjustable in varying increments for each individual gear. Most of your ratio changes will be made at the rear end in the differential.

The most important factor in selecting proper transmission ratios, is to make sure your not geared to high causing excessive wheel spin. You must also be sure you have a good split between ratios through all 4 gears. You'll want to maintain as high an rpm as possible when shifting through the gears.

To large a split ratio between gears will cause slow acceleration and lost time whenever shifting is required. For successful gear shifting, remember that it is critical to ensure that all mechanical elements between the drivers hand and the dog faces are in good order and properly set. This includes the gear linkage in the chassis! Successful up-shifting, defined as fast and non dog-damaging will be achieved by fully moving the dog ring as rapidly as possible from one gear to the next, preferably with the engine's driving load removed until the shift is completed.

The opposite is true of a synchromesh gearbox as used in passenger cars, where slow movement helps. It should be remembered that it is not possible to damage the dogs when fully engaged in gear.

If a driver moves the gear lever slowly, or if the linkage is not rigid and effective, dog wear will occur. We always recommend lightweight yet solid rod linkage, not cables ideally. I list below the different methods of up-shifting that are used in racing most commonly. The best at the top, the worst at the bottom: Automated semi automated.

Gear-shifts take milliseconds. This system produces zero dog wear when set up well. It is not applicable to most cars, but it illustrates that speed of shift is a good thing.

Manual with engine cut. This system is almost as good as an automated one as long as the driver pulls the lever very quickly. Again it is not applicable to many cars, but it illustrates that speed of shift is a good thing.

With this system it is especially important to move the lever ultra fast, otherwise the engine will be reinstated during partial dog engagement, causing damage. The damage can usually be felt by the driver. Manual Best method: With no assistance from the engine management, the driver must lift off the throttle sufficiently to allow the dog ring to be pulled out of engagement.

He should then stay off the throttle long enough to allow the dog ring to engage with the next gear. In practice, the driver can move the gear lever faster than he can move his foot off and back on to the throttle. Therefore the effective method is to apply load to the gear lever with your hand and then lift the throttle foot off and back on to the pedal as fast as physically possible.

In lifting your foot, the loaded gear lever will almost involuntarily flick to the next gear before the foot is re-applied to the throttle. Another method is to load the gear lever with your hand, stay flat on the throttle and dab the clutch to release the dog ring.

The overall effect on the gear shift is similar to the above method, but clutch wear may become a big issue. The method causes unnecessary clutch wear, does absolutely nothing to help come out of gear and usually causes dog wear whilst engaging the next gear. This wear is due to several reasons. Firstly, it is impossible for a driver to co-ordinate the complicated sequence of all five physical movements accurately.

Consequently the engagement dogs often find themselves engaging whilst the throttle is applied. Successful down-shifting, has similar rules applied regarding speed of shift. Unloading the dogs is done in the opposite manner obviously. Whilst braking, the dogs must be unloaded by either touching the throttle pedal or- my preferred method- by dipping the clutch.

However, one sharp dab of clutch or throttle is appropriate per shift. Continued pressure on either will cause dog damage for different reasons. Wedge The wedge can be adjusted by clicking the weight bias tab on the garage screen. Wedge is also known as cross weight or diagonal weight. Wedge is used to keep the back of the car tight entering a corner while also adding bite exiting a corner. A setup that will spin it's tires easily will require more wedge to counter act the traction loss under power.

A setup with a higher gear ratio or one that does not spin the tires will require less wedge. Wedge is required to get through the corners. You might think that by changing wedge you would change left side or front bias, but that isn't the case.

Increasing wedge will tighten the chassis. Decreasing wedge will loosen the chassis. Wedge synopsis: Increasing wedge tightens the chassis. Decreasing wedge loosens the chassis. Steering linearity can effect the way your car performs through the corners. The reason this option is available to use is because of all the available steering devices on the market. Although I don't suggest it, you are able to race with a joystick, as well as every type of wheel device you can imagine.

Not all steering devices are created equal. Various manufactures provide different degrees of wheel movement. Steering linearity allows us an adjustment to compensate for the differences in steering devices. As a general rule, most steering wheel devices will provide better precision when set towards a higher linear setting than low.

Joystick users would probably prefer a lower non-linear setting. With non-linear steering, the steering is slower when the controller is close to center position and progressively quickens the more you turn the controller. At a lower or non-linear setting, you will need to turn your wheel more to enter a corner, but you may experience a more comfortable feel, which will allow you to make better or more accurate steering decisions.

There is no right or wrong answer when it comes choosing the proper steering linearity. A loose setup may work better with a different linearity setting than a tight setup. Adjusting your linearity can change your lap times for the better or worse. It can also change your tire wear for the better or worse. Adjusting your steering ratio along with your linearity will provide you with even more or less steering feedback. Don't be afraid to experiment with this option.

You may find yourself changing your linearity settings based on how tight the turning radius is for the track your competing at. Either way, experimentation is the only way your going to find out what is comfortable for you. Qualifying Chassis Adjustments There are two distinct differences in NASCAR Racing as compared to N4; first, we now get two laps of qualifying at every oval track, second, we have to use the race motor.

Even though we get two laps, we shouldn t waist the first lap for any track except the superspeedways. Often times you ll find that the first lap is the quickest. There are probably two main philosophies about qualifying setups; we could build something that's very radical but it drives much differently than our race setup or we could build something that basically drives the same as our race setup but we take advantage of the fact that we re not concerned with tire wear at all so we build a setup that we can drive hard for two laps and not have to worry about changing our driving style that much.

I prefer that latter philosophy. The next section talks about the chassis adjustments I may make and the order I make them. Chassis Adjustments: Tire Pressures: The first thing we want to do is add some tire pressure to reduce rolling drag and bring the temps up quicker so we get maximum bite. We don t want to raise tire pressures so much though that we lose bite because we ve severely reduced the tires contact patch by crowning it too much.

Typically, we want the tires to crown about degrees. Tape: Next we add tape but at most tracks you re not going to be able to tape the whole grille up or you ll blow the motor before you ve completed two laps. As a matter of fact, you ll want to baby the car through the gears as you re pulling off pit lane.

Remember that adding tape increases front down force which will loosen the car up some. Wedge: If you use any negative wedge on your race setup, put the wedge back to neutral which will offset the added down force of increased tape. Final Drive ratio: I use a taller 4th gear than I think I need especially at the short tracks where rear wheel spin can rob you of serious time. DO NOT use rear wheel spin to turn the car during qualifying. If the rev idiot light comes on at the end of the straights, 4th gear is too short.

A chassis that pushes on exit also robs you of time. Use the front sway bar to fine tune that. Camber: In NASCAR Racing, the true measure of camber may not show up for 15 or more laps and we already know that we don t want our tire temp spread to be any more that 10 degrees across the tire for maximum grip.

Again, this is much improved over N4 So for qualifying we may want to add a bit more negative camber to the RF and positive to the LF. Forward Weight: Since we have the car gripping a little better up front because of the tape and camber and we re probably going to enter the corners a bit faster, we may want to move weight forward a little for stability on corner entry.

We don t want to make drastic changes here or it will throw off how the car handles in the middle, therefore how we drive the car. Rear Spring split: To overcome moving weight forward and increased corner entry speeds, I increase the split in the rear springs which further stabilizes the car on entry and helps the car turn better from the middle off.

For race setups, I use very little rear split because as the RF tire wears a big rear split has a tendency to make the car snap loose on exit. Springs: Stiffer springs can give you slightly better straight speeds but at the cost of handling. If you do stiffen or soften the springs, you ll want to do evenly on all 4 corners to keep the chassis handling about the same.

You can measure this by using roll couple. Shocks: If anything, I may increase the compression stiffness of the RF shock which allows the weight to stay on the left a little longer remembering that we really don t care about tire wear here.

For race setups, a stiff RF compression will cause the RF to scrub more thereby wearing it out quicker. Sway bars: I may increase the front sway bar some if the car is a little too loose. Roll couple does not matter in a qualifying setup except that drastically changing the roll couple will change the overall handling characteristics of the car.

Remember our goal through this whole process is to make the car quicker but not change how we drive it very much if at all. Those tracks have straights long enough and the corners are banked enough to warrant the decreased drag at the expense of down force. Caster: The very last thing I change because I normally have the way I want it from my race setup. From a driving standpoint, we re not concerned with tire wear but remember that sliding the car excessive squealing of the tires through the corners robs you of time.

You definitely have to have the mindset of driving the car as hard as possible but even smoother than you do during a race. Please use this section only as a general guide. You may not see the same exact results as mentioned below. Other component settings may mask changes made in different areas. Adjustments in other areas may be needed first before you see some of the changes indicated below in certain areas.

All troubleshooting answers assume the rest of the chassis is already set correctly or close to being correct. Car turns into a corner too quickly or becomes loose. Too much negative LF camber: Inside of tire excessively hot. Reduced pull to the left entering a corner.

Chassis will tighten up from the middle out. Too much negative RR camber: Inside of tire excessively hot. Tight condition from the middle out. Too much negative LR camber: Inside of tire excessively hot. Loose condition entering a corner. Too much positive RF camber: Outside of tire excessively hot.

Too much positive LF camber: Outside of tire excessively hot. Increased pull to the left entering a corner. Chassis will loosen up from the middle out. Too much positive RR camber: Outside of tire excessively hot. Loose condition from the middle out. Too much positive LR camber: Outside of tire excessively hot. Tight condition entering a corner. Not enough caster: Car too sensitive, steering becomes twitchy.

Very little steering feel, less effort is required to turn. Car will pull towards the side with less caster. Car will feel loose entering a corner. Loss of traction or wheel spin when accelerating. Loss of top speed at the end of a straight-away. Too low a ratio: Low rpms. Car feels sluggish upon acceleration. Car feels under powered. Not enough front bias: Will cause car to be loose. Not enough front brake bias: Will cause car to become loose while braking.

Car pushes through the corners. Car may get tighter as you progress through turn. Car is slow to respond when changing directions. Car may not take set in the corner. Car will want to push. Car may wander under heavy braking. Too much toe in: Car turns into a corner quicker than it should with very little wheel movement. Potential engine damage. Increased speeds Front end will stick extremely well causing a loose condition.

Not enough tape: Cool engine temperatures. Slower top speeds. Little or no front down force will cause the car to push. Car will turn left much easier than right. Car will loosen itself up when negotiating left hand turns. Not enough left bias: Car will not turn left into a turn as easy. Car will turn right much more easier. Car will feel tight when negotiating left hand turns.

Too small a rear sway bar: Car will feel tight. On the rear will increase straightaway speeds. Too high a ride height: On the LR will loosen the chassis. On the LR may cause the RF to bottom out. On the RF will tighten the chassis. Car will also push while accelerating exiting a corner. Front shocks too weak: Car will be loose entering a corner while braking. Car will also feel loose exiting a corner while under acceleration.

Rear shocks too stiff: Car will be loose entering a corner while braking. Rear shocks too weak: Car will push entering the corner while braking. Chassis will feel tight while cornering. Too low a spoiler: Quicker straight-away speeds. Chassis will feel loose while cornering. Front springs too weak: Car will Under steer. Excessive body roll. Mid turn push. Rear springs too stiff: Car will Over steer when accelerating.

Excessive wheel spin. Rear springs too weak: Car will Under steer. Excessive rear squat when accelerating possibly bottoming out. Car will roll over onto the RR. Car may be slow to take a set. RF too stiff: Car will push or Under steer. RF too weak: Car will be loose or Under steer. LF too stiff: Car will be loose or Under steer. LF too weak: Car will push or Under steer.

RR too stiff: Car will be loose or Under steer. RR too weak: Car will push or Under steer. LR too stiff: Car will push or Under steer. LR too weak: Car will be loose or Under steer. More steering required to negotiate a corner. Too low a ratio: Quick steering response. Very little steering needed to negotiate a corner.

Car feels sensitive or twitchy. Car will Under steer. Front pressure too high: Cooler tire temperatures. Higher temp. Rear pressure too low: Excessive heat in tire. Car will Over steer. Rear pressure too high: Cooler tire temperatures.