Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Understeer shopping experience:
1. Compare - without doubt the biggest advantage that the Understeer offers shoppers today is the ability to compare thousands of Understeer at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.
2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about
3. Testimonials - don't know anybody that has bought a Understeer? Wrong! If the Understeer is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.
4. Questions - Got a question about Understeer then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....
5. Reputation - Never heard of the company selling Understeer? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Understeer and build up a picture of their reputation for sales, returns, customer service, delivery etc.
6. Returns - still worried that even after all of the above your Understeer wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.
7. Feedback - happy with your Understeer then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.
8. Security - check for the yellow padlock on the Understeer site before you buy, and the s after http:/ /i.e. https:// = a secure site
9. Contact - got a question about Understeer, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.
10. Payment - ready to pay for your Understeer, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.
Understeer is a term for a car handling condition during cornering in which the circular path of the vehicle's motion is of a markedly greater diameter than the circle indicated by the direction its
wheels are pointed. The effect is opposite to that of the oversteer and in simpler words understeer is the condition in which the front tires don't follow the trajectory the driver is trying to impose while taking the corner, instead following a more straight line trajectory.
This is also often referred to as pushing, plowing, or refusing to turn in. The car is referred to as being 'tight' because it is stable and far from wanting to spin.
As with oversteer, understeer has a variety of sources such as mechanical traction, aerodynamics and suspension.
Classically, understeer happens when the front tires have a loss of
traction (engineering) during a cornering situation, thus causing the front-end of the vehicle to have less mechanical grip and become unable to follow the trajectory in the corner.
In modern
race cars, especially open wheel cars, understeering is caused mainly due to the
Automotive aerodynamics configuration. In this respect, the lack of a heavy aerodynamic load (downforce) in the front side prevents the front tires from gaining enough traction. At the same time understeer can be caused by having a heavier aerodynamic load at the rear end of the car giving the rear tires more traction than the front tires. Also, suspension balance should take into account the types of surfaces being driven - differing levels of friction in each surface influence the potential understeer behavior.
Suspension (vehicle), tire pressure and centre of gravity are important factors that determine the understeer/oversteer handling condition.
Understeer covers several different phenomena, in particular, there is a big difference between linear range understeer, typically between 0 and 0.4g, and limit handling understeer, which is at higher lateral accelerations, and is what racing drivers are talking about.
Common practice
It is common practice among automobile manufacturers to configure production cars deliberately to have a slight linear range understeer by default. If a car understeers slightly, it tends to be more stable (within the realms of a driver of average ability) if a violent change of direction occurs, improving safety. However, if the owner fits new tires to the front axle only, they will tend to reduce the understeer margin, which can cause handling problems, as claimed in San Luis Obispo County Court Case CV078853, and others. . The recommendation from most manufacturers when replacing only two tires is to fit the unworn ones to the rear, and the best of the old ones to the front axle, for this reason. However, this is not ideal either.
Physics
Under all high speed (greater than approximately 10mph (15 km/h) for a typical automobile) cornering conditions a wheeled vehicle with pneumatic
tires develops a greater lateral (i.e. sideslip) velocity than is indicated by the direction in which the wheels are pointed. The difference between the circle the wheels are currently tracing and the direction in which they are pointed is the
slip angle. If the slip angles of the front and rear wheels are equal, the car is in a neutral steering state. If the slip angle of the front wheels exceeds that of the rear, the vehicle is said to be
understeering. If the slip angle of the rear wheels exceeds that of the front, the vehicle is said to be
oversteer.
An old bit of
auto racing humor says that an understeering car goes through the fence nose first, an oversteering car goes through the fence tail first, and with a neutral-steering car, both ends go through the fence at the same time.
Design
Any vehicle may understeer or oversteer at different times based on road conditions, speed, available traction, and driver input. The design of a vehicle, however, will tend to produce a particular "terminal" condition when the vehicle is pushed to and past its limits of adhesion. "
Terminal understeer" refers to a vehicle which, as a function of its design, tends to understeer when cornering loads exceed tire traction.
Terminal handling balance is a function of front/rear relative roll resistance (suspension stiffness), front/rear weight distribution, and front/rear tire traction. A front-heavy vehicle with low rear roll stiffness (from soft spring (device) and/or undersized or nonexistent rear
anti-roll bars) will have a tendency to terminal understeer: its front tires, being more heavily loaded even in the static condition, will reach the limits of their adhesion before the rear tires, and thus will develop larger slip angles.
Front-wheel drive cars are also prone to understeer because not only are they usually front-heavy, transmitting power through the front wheels also reduces their grip available for cornering. This often leads to a "shuddering" action in the front wheels which can be felt in the car as grip is suddenly being changed from planting the engines power on the road and steering. This is why rear wheel drive cars tend to handle better as the rear wheels main job is to handle the engines
torque and the front wheels to steer.
Although understeer and oversteer can each cause a loss of control, many automakers design their vehicles for terminal understeer in the belief that it is easier for the average driver to control than terminal oversteer. Unlike terminal oversteer, which often requires several steering corrections, understeer can often be reduced simply by reducing speed. A slight danger in some cars which traditionally understeer is actually sudden oversteer. So for example if a car is driving hard and understeering, the driver may be tempted to take his foot off the accelerator (increasing steering effectiveness of the front wheels as there is no engine torque to deal with) causing the car to
lift-off oversteer and spin, often without warning. Not many production cars react like this, as it is not a desirable characteristic.
Understeer is not just present during acceleration through a corner, it can also be found during heavy braking. If the brake balance (the strength of the brakes in terms of the front and rear wheels) is too heavy at the front this can cause understeer. This is caused by the front wheels locking and losing any effective steering. The opposite is true if the brake balance is too strong towards the rear wheels causing the rear end to spin out (like a child skidding on a bicycle). In ordinary road cars a safe brake balance (tending towards slight understeer) must be found.
Racing drivers, on asphalt surfaces, generally prefer a neutral condition (with a slight tendency toward understeer or oversteer, depending on the track and driver preference) because both understeer and oversteer conditions will scrub off speed while cornering. In rear wheel drive cars understeer is generally faster on a circuit because the rear wheels need to have some grip available to accelerate the vehicle out of the turn.
In a straight line, or when cornering gently (typically up to 0.4g) the characteristic is called linear range understeer. This is a difficult characteristic to sense directly, but is responsible for many important facets of the handling in this regime, including step steer response, frequency response, and yaw gain linearity. Usually this is developed using a
Bundorf analysis.
Understeer values
How much a car understeers can be measured in the number of degrees
more the steering wheel have to be turned per G of lateral acceleration. Here are the measured linear range values for some cars. The higher the number the more the car understeers.
{| border="1" cellpadding="5" cellspacing="0"|-! style="background:#efefef;" | Car model! style="background:#efefef;" | Understeer value|-|
Nissan 350Z| 21|-| [Nissan 350Z Roadster] GT| 22|-|
Renault Megane Sport]| 23|-| Mini Cooper S]| 25|-| Alfa Romeo 147 GTA]| 27|-|
Corvette Z06 111R| 28|-| [Porsche 997 Carrera S] Aero combi| 28|-|
Škoda Octavia RS] Carrera| 29|-|
Porsche Cayman S] GTI| 29|-|
Porsche 987 Boxster S]| 32|-| Range Rover Sport Supertech] ST| 33|-| Mitsubishi Lancer EVO8]CS| 34|-|
Audi RS4| 35|-| [BMW Z4 Roadster M] Comp Package| 36|-|
Opel Astra OPC] 3.0i| 37|-| Subaru Impreza WRX STi] 3.0 aut| 38|-| Volvo V70 T5] 2.0 T Q| 41|-| Mercedes E55 AMG] V6 3.2 Q Avant| 43|-|
Porsche Cayenne Turbo] ForFour Brabus| 45|-|
Mercedes SLK 350]| 49|-| Alfa Romeo 159 2.2 JTS] Roadster V6| 71|}
Notes
See also
External Links
- Effect of narrow rear track on understeer
- Driving Fast - Understeer
de:Untersteuernes:Subvirajenl:Onderstuur (auto)ja:アンダーステアpl:Podsterownośćpt:subviragem
Understeer is a term for a car handling condition during cornering in which the circular path of the vehicle's motion is of a markedly greater diameter than the circle indicated by the direction its
wheels are pointed. The effect is opposite to that of the oversteer and in simpler words understeer is the condition in which the front tires don't follow the trajectory the driver is trying to impose while taking the corner, instead following a more straight line trajectory.
This is also often referred to as pushing, plowing, or refusing to turn in. The car is referred to as being 'tight' because it is stable and far from wanting to spin.
As with oversteer, understeer has a variety of sources such as mechanical traction, aerodynamics and suspension.
Classically, understeer happens when the front tires have a loss of traction (engineering) during a cornering situation, thus causing the front-end of the vehicle to have less mechanical grip and become unable to follow the trajectory in the corner.
In modern race cars, especially open wheel cars, understeering is caused mainly due to the Automotive aerodynamics configuration. In this respect, the lack of a heavy aerodynamic load (downforce) in the front side prevents the front tires from gaining enough traction. At the same time understeer can be caused by having a heavier aerodynamic load at the rear end of the car giving the rear tires more traction than the front tires. Also, suspension balance should take into account the types of surfaces being driven - differing levels of friction in each surface influence the potential understeer behavior.
Suspension (vehicle), tire pressure and
centre of gravity are important factors that determine the understeer/oversteer handling condition.
Understeer covers several different phenomena, in particular, there is a big difference between linear range understeer, typically between 0 and 0.4g, and limit handling understeer, which is at higher lateral accelerations, and is what racing drivers are talking about.
Common practice
It is common practice among automobile manufacturers to configure production cars deliberately to have a slight linear range understeer by default. If a car understeers slightly, it tends to be more stable (within the realms of a driver of average ability) if a violent change of direction occurs, improving safety. However, if the owner fits new tires to the front axle only, they will tend to reduce the understeer margin, which can cause handling problems, as claimed in San Luis Obispo County Court Case CV078853, and others. . The recommendation from most manufacturers when replacing only two tires is to fit the unworn ones to the rear, and the best of the old ones to the front axle, for this reason. However, this is not ideal either.
Physics
Under all high speed (greater than approximately 10mph (15 km/h) for a typical automobile) cornering conditions a wheeled vehicle with pneumatic tires develops a greater lateral (i.e. sideslip) velocity than is indicated by the direction in which the wheels are pointed. The difference between the circle the wheels are currently tracing and the direction in which they are pointed is the
slip angle. If the slip angles of the front and rear wheels are equal, the car is in a neutral steering state. If the slip angle of the front wheels exceeds that of the rear, the vehicle is said to be
understeering. If the slip angle of the rear wheels exceeds that of the front, the vehicle is said to be
oversteer.
An old bit of auto racing humor says that an understeering car goes through the fence nose first, an oversteering car goes through the fence tail first, and with a neutral-steering car, both ends go through the fence at the same time.
Design
Any vehicle may understeer or oversteer at different times based on road conditions, speed, available traction, and driver input. The design of a vehicle, however, will tend to produce a particular "terminal" condition when the vehicle is pushed to and past its limits of adhesion. "
Terminal understeer" refers to a vehicle which, as a function of its design, tends to understeer when cornering loads exceed tire traction.
Terminal handling balance is a function of front/rear relative roll resistance (suspension stiffness), front/rear weight distribution, and front/rear tire traction. A front-heavy vehicle with low rear roll stiffness (from soft spring (device) and/or undersized or nonexistent rear
anti-roll bars) will have a tendency to terminal understeer: its front tires, being more heavily loaded even in the static condition, will reach the limits of their adhesion before the rear tires, and thus will develop larger slip angles. Front-wheel drive cars are also prone to understeer because not only are they usually front-heavy, transmitting power through the front wheels also reduces their grip available for cornering. This often leads to a "shuddering" action in the front wheels which can be felt in the car as grip is suddenly being changed from planting the engines power on the road and steering. This is why rear wheel drive cars tend to handle better as the rear wheels main job is to handle the engines
torque and the front wheels to steer.
Although understeer and oversteer can each cause a loss of control, many automakers design their vehicles for terminal understeer in the belief that it is easier for the average driver to control than terminal oversteer. Unlike terminal oversteer, which often requires several steering corrections, understeer can often be reduced simply by reducing speed. A slight danger in some cars which traditionally understeer is actually sudden oversteer. So for example if a car is driving hard and understeering, the driver may be tempted to take his foot off the accelerator (increasing steering effectiveness of the front wheels as there is no engine torque to deal with) causing the car to
lift-off oversteer and spin, often without warning. Not many production cars react like this, as it is not a desirable characteristic.
Understeer is not just present during acceleration through a corner, it can also be found during heavy braking. If the brake balance (the strength of the brakes in terms of the front and rear wheels) is too heavy at the front this can cause understeer. This is caused by the front wheels locking and losing any effective steering. The opposite is true if the brake balance is too strong towards the rear wheels causing the rear end to spin out (like a child skidding on a bicycle). In ordinary road cars a safe brake balance (tending towards slight understeer) must be found.
Racing drivers, on asphalt surfaces, generally prefer a neutral condition (with a slight tendency toward understeer or oversteer, depending on the track and driver preference) because both understeer and oversteer conditions will scrub off speed while cornering. In rear wheel drive cars understeer is generally faster on a circuit because the rear wheels need to have some grip available to accelerate the vehicle out of the turn.
In a straight line, or when cornering gently (typically up to 0.4g) the characteristic is called linear range understeer. This is a difficult characteristic to sense directly, but is responsible for many important facets of the handling in this regime, including step steer response, frequency response, and yaw gain linearity. Usually this is developed using a Bundorf analysis.
Understeer values
How much a car understeers can be measured in the number of degrees
more the steering wheel have to be turned per G of lateral acceleration. Here are the measured linear range values for some cars. The higher the number the more the car understeers.
{| border="1" cellpadding="5" cellspacing="0"|-! style="background:#efefef;" | Car model! style="background:#efefef;" | Understeer value|-| Nissan 350Z| 21|-| [Nissan 350Z Roadster] GT| 22|-| Renault Megane Sport]| 23|-|
Mini Cooper S]| 25|-|
Alfa Romeo 147 GTA]| 27|-| Corvette Z06 111R| 28|-| [Porsche 997 Carrera S] Aero combi| 28|-|
Škoda Octavia RS] Carrera| 29|-| Porsche Cayman S] GTI| 29|-| Porsche 987 Boxster S]| 32|-| Range Rover Sport Supertech] ST| 33|-| Mitsubishi Lancer EVO8]CS| 34|-| Audi RS4| 35|-| [BMW Z4 Roadster M] Comp Package| 36|-|
Opel Astra OPC] 3.0i| 37|-| Subaru Impreza WRX STi] 3.0 aut| 38|-| Volvo V70 T5] 2.0 T Q| 41|-| Mercedes E55 AMG] V6 3.2 Q Avant| 43|-| Porsche Cayenne Turbo] ForFour Brabus| 45|-| Mercedes SLK 350]| 49|-| Alfa Romeo 159 2.2 JTS] Roadster V6| 71|}
Notes
See also
External Links
- Effect of narrow rear track on understeer
- Driving Fast - Understeer
de:Untersteuernes:Subvirajenl:Onderstuur (auto)ja:アンダーステアpl:Podsterownośćpt:subviragem
