Driving ability aside, there’s a technical explanation to why a car like that can achieve such feats. The car is most likely getting more out of its chassis put to use than its competitors. Most experienced drivers understand where to look to pull out that hidden potential. While every car behaves differently, learning to discern how and why brings you closer to both correctly setting up a car, and controlling it like an expert. That ability is directly linked to how well we understand Vehicle Dynamics.
When diving into what Vehicle Dynamics is all about, a good place to start is two commonly used terms: Oversteer and Understeer.
These terms refer to two opposite ways a car chassis wants to move while cornering; when trying to turn, one wants to turn too much and the other not at all. Too much of either can be deadly on track, but a touch of each can translate to a fast car. While you can adjust to these with driving technique, we need to keep in mind the car has it’s natural limits. Understanding how these two behaviors affect the car will help us make critical decisions when we eventually try to push past those limits by changing and tuning components on your car. Rather than fight them for control of the car, we want to use them to our advantage as we attempt that next fastest lap time.
Oversteer takes place when your car rotates more than the amount of your steering input. For example, if you turn your steering wheel ⅛ of a turn, but the car continues to turn after its completed that amount of rotation - you’re now experiencing oversteer. This occurs when the rear tires are put under too much stress and break grip before the front tires do. Too much oversteer can cause spin outs or the rear slamming the wall after kicking out too far. However, when in control, oversteer allows you the tightest racing line which can give you the fastest way around a corner. A little oversteer is considered a good thing in race car design.
Understeer takes place when the car stops rotating before the intended amount of steering input is completed. If you turn the steering wheel, but the car stops rotating and no matter how much steering you add in that direction, the momentum of the car continues in the same direction - You're now experiencing understeer. This occurs when the front tires break grip before the rears. Too much understeer will make the vehicle feel “lazy” and “unresponsive”, not rotating when you ask it to. However, understeer characteristics will add stability when traveling at high speeds and is more predictable to drivers who aren't accustomed to oversteer. It is actually the standard in most road cars and often considered more safe by car manufacturers.
::Oversteer Drive Line
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::Neutral Drive Line
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::Understeer Drive Line |
(NEO TIP: In most scenarios, we attempt to set up a car to perform as most neutrally as possible. The idea is to find the balance between the two where neither is obstructing the way you take the corner. In race scenarios, we are ideally looking for the car to be both as fast and stable around every corner as possible. A neutral vehicle dynamic makes it the best starting point if adjustments are needed on the track.)
When we look at what the tires are doing in both of these scenarios, one set or both sets of tires are losing grip between the rubber and the asphalt. As we arrive at a corner and begin to turn, the wheels rotate and the driving force causes the tires to slide (or slip). In this state, the tires are pointed in a slightly different direction than the one they are traveling. The difference between the two is what we call the slip angle. When the tire has lost all traction, turning the steering wheel deeper into the corner will only widen the slip angle. If the rear slip angles are wider than the front, we are inducing oversteer. In the opposite scenario, we are inducing understeer. The closer the front and rear slip angles are- the more neutral the behavior becomes. |
Now that we understand Oversteer and Understeer a bit more, we can look at a couple of the factors, Grip & Traction, and Weight Transfer, that is related to them that will help us understand why they happen. Our focus is on what is actually happening to the tires, and the forces applied to it that cause the dynamics of these two behaviors.
Traction occurs when the rubber of the tires meet the asphalt of the road at the right temperatures causing friction that keeps the wheels (and the entire vehicle) on the ground while in motion. The rubber has a temperature range where it is at its optimal performance. Too low or too high a temperature will result in the tire not taking grip or breaking grip, causing them to slide. When we overwork or put too much pressure on the tires, we are causing the tires to generate too much heat at which point they will break traction. The goal is to keep the tires at the optimal temperatures for as long as possible. |
Accelerating, braking, and cornering hard are all things that put stress on the tires. By doing this you’re shifting the weight of the vehicle onto two of the four tires in all of the scenarios. This is called Weight Transfer. Every car has a center of mass, (sometimes referred to as center of gravity) that sits between the front and rear wheels. This imaginary point shifts with the way we move the vehicle, and that shift is called the “Moment of Inertia”. To reduce oversteer or understeer, the goal is to keep this moment of inertia as small as possible. Setting up the car correctly can take some of the stress off of the tires during weight transfer. Stiffer springs in the front for example take some of the stress off the tires and onto the springs instead, reducing the amount of understeer that could occur. Most performance tuning done on the chassis is to contribute to a more favorable vehicle dynamic in this fashion.
These are the things that attribute to what we call Vehicle Dynamics. Understanding how the car wants to move or behave is the first step toward learning how to push your car to its limits as a driver. Once we get to the point where the car doesn't feel like there is any more to give- that is when we start modifying or adjusting parts. There are more ways than you count when it comes to changes you could make to your car, but understanding your car’s vehicle dynamics will ultimately make those decisions much easier to suiting your driving style.
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The true goal of suspension tuning is to improve how the car handles; in other words, its ability to maintain a course through turns, braking, different surfaces, and weather conditions. To keep the right course, you’ll start by Increasing ground contact or tire grip as you travel through a corner.
If your car is too stiff, it will bounce around on rough roads or during hard braking. If it’s too soft, it won’t be able to maximize your driving experience because it won’t allow you to control your vehicle. The trick is finding the right balance between these two extremes so that you have enough grip but not too much bounce.
As disc brake starting to show signs of a brake pull or noise, it is time to perform a routine caliper maintenance. One of the most common brake caliper issue is the caliper piston fails to retract. In order for the wheels to rotate freely, a tiny air gap must exist between the rotor and brake pad. When the pads on one wheel drag against the rotor, the pad may glaze or the brake assembly temperatures may increase enough to change the coefficient of friction causing uneven pressure between the pad and rotor surface resulting in brake-pulling.
A friendly reminder, a low master cylinder reservoir fluid level might indicate that the brake pads are excessively worn. Brake fluid supplied by the reservoir is used to fill the caliper bore as the caliper piston extends to compensate for pad wear. In any case, a low fluid level at the master cylinder reservoir indicates the need for a thorough brake system inspection.
Brake pad wear can be an indicator of caliper condition. If the inside pad is more worn than the outside pad, there exist the possibility that one or more of the brake caliper piston may be seized. Either type of caliper — fixed or floating — will cause the brake pads to drag against the rotor when the pistons are seized into the caliper bores. In addition, the caliper boot should not show any signs of fluid leakage nor should the caliper boot appear hardened or cracked. The piston will eventually corrode and seize in place if a defective caliper boot allows moisture to accumulate between the caliper bore and piston.
Calipers with integrated parking brake hardware should be inspected for fluid leakage and correct parking brake operation, and service brake pedal travel. In some applications, the parking brake must be used regularly to compensate for brake pad wear. Excessive service brake pedal travel may result if the driver doesn’t use the park brake regularly or if the parking brake cable or caliper hardware is seized.
Although you’re not likely to rebuild a disc brake caliper in the near future, it still pays to understand how in case, you find yourself rebuilding the original calipers on a classic or collector import vehicle.
First, it’s important to establish safe work habits before beginning any hydraulic brake service by consulting an appropriate service manual. The pressure in the anti-lock brake accumulator should be released by pumping the brake pedal as specified by a service manual or until the pedal feels hard. Next, the bleeder screw should be loosened to allow old fluid to be flushed out of the caliper bore. In some cases, a clogged bleeder screw must be removed for cleaning or replacement. If the bleeder screw is seized, it’s probably cheaper to replace the caliper.
There are two methods of thought on preventing debris from being flushed into the anti-lock braking and master cylinder assemblies when the piston is seated in the caliper bore. The first method opens the bleeder screw to relieve pressure as the caliper piston is seated. The second method clamps the brake hose closed with a pair of hose-clamping pliers to prevent debris from back-flushing into the master cylinder. The first method is the most commonly accepted because there’s less chance of inadvertently damaging the hose.
Seized caliper pistons can be difficult and dangerous to remove, so be cautious. Perhaps the safest method is to bottom the piston with a common C-clamp to push out excess fluid, and then ease the piston from the bore by gently applying air pressure to the brake hose port while backing out the C-clamp screw.
When the piston is ready to exit the bore, cover the caliper assembly with a shop towel to prevent the brake fluid from spattering. If the piston is so badly seized that it doesn’t respond to controlled air pressure, the caliper should be replaced.
Because the piston surface seals the brake caliper, the piston should be in like-new condition. If the piston is pitted or scored, it should be replaced.
Replacing the dust seals often requires a dedicated tool to guide the seals into the caliper bore. The most common method for installing the piston into the boot is to hold the piston in place with a piston seating tool while inflating the boot with compressed air. This method works well on small-bore calipers. Boot expansion tools must generally be used on large-bore calipers with shallow-boot designs.
The piston must be perfectly square with the bore before it will pass through the flat-cut O-ring in the caliper bore. The simplest method is to use a square bar to gently rock the piston from side-to-side until it drops into the caliper bore.
Once the piston is installed, carefully remove the caliper guide pins and lubricate them with synthetic caliper grease or the OEM-recommended lubricant. When installing the caliper bracket bolts, apply thread-locking compound, if required. In other cases, lightly oil the bolts and torque them to specification. Always install new caliper hardware on the caliper bracket to prevent pad rattle and dampen pad squeal.
A correctly serviced caliper should slide smoothly on its guide pins or guide surfaces, and should allow the rotor to turn freely when brake pedal pressure is released. If the caliper won’t release, the interior rubber of the brake hose might be peeling and blocking the return of fluid to the master cylinder reservoir. In other cases, the master cylinder push rod or brake pedal height might be incorrectly adjusted, which prevents the master cylinder from releasing the fluid pressure from within the caliper.
The wheel studs on a car acts as a clamping force that holds the wheel to the hub. When we go to tighten the lug nuts, the wheel studs act like a spring providing elastic force to hold the wheel on properly. The specific torque spec for the vehicle tightens the studs at 90% of its elastic limit yielding the highest possible force to hold the wheel to the hub.
This is very important because of the coefficient of friction involved in holding the wheel on the hub. Generally, the more clamping force to hold the wheel onto the hub, more force it requires for the wheel to slip on the hub. That being said, there cannot be any bending load on the stud.
Why do we need to consider the coefficient of friction? Because this is the ratio of normal force at the contact of the two surfaces to the lateral force required to slip the bodies relative to one another. Performance street tires have a coefficient of friction of 0.9. What does this mean? This means at 100lb of vertical force, there exist 90lb of corning force before it slides.
As the car moves, the stress on the wheel studs does not change unless one of the vertical component of any external force applied to the wheel exceed the clamping force and causing the wheel in place to slip on the hub. The wheel studs then is loaded and may bend, sheer or in some cases break.
If, there isn’t sufficient clamping force or there is too much clamping force between the wheel and the hub, there will be flexing and the tension load on the wheel studs then drop to zero. With no tension load on the stud, the clamped joint is no longer tight. This results in a bending load on the wheel studs and thus the wheel let go. This is how wheels fall off on cars.
By Inserting a wheel spacer between the hub and wheel will changes nothing to the physics of holding the wheel on. By utilizing longer wheel studs for wider wheel spacers will have no negative effects to the wheel and hub. The key is to have quality wheels, hub and spacer that are rigid and stuff. What causes failure is flexing and loss of clamping force. A properly installed wheel spacers are perfectly safe. Always check the torque required for your specific car when installing wheel spacers.
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What kind of braking does it require to set new Street FWD record at SLB 2015?
Here are a few facts for you.
But can technology change how brake systems work - and transform the hot thermal energy into cold? Sounds impossible, right?
But it isn't. With the innovative technology known as brake ducting, the braking equipment gets a true upgrade. Moreover, the 'ducting' in the term refers to actual ducting around the cooling system of the brakes, more precisely the upright, caliper and drillings in the friction material.
The brake ducting testing has founds its greatest use in the racing sports, in which the cars are cooled by forcing air throught the ducts and blowing it through the vents of the disc - therefore ventilating it and the surface of the pads and discs.
Wondering about what are the most positive effects of brake ducting?
First and foremost is the aerodynamic efficiency. While smaller discs are used for circuit racing events in which there is less braking in order to manage the temperature of the brake. Recently, a loophone in the Technical Regulations of Formula 1 has allowed the brake ducting technology to be applied directly to the wheels, and the Red Bull RB10 masterpiece has leveraged a brake cooling duct as one of the most innovative and efficient aerodynamic devices found in this sport.
The main loophole which introduced the brake ducting technology to a sport like the Formula 1 comes from a lack of definition of what actually constitutes a duct. Although the FIA can ban this type of innovative technology, they have certainly seen its effects and have decided to let this technology remain.
In the end, while slowing down the cars in a more effective way, the brake ducting technology also gives a vehicle downforce, which allows safer and efficient braking and precise aerodynamics - all coming from a simple method that redefined how the braking technology functions in racing sports.
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