Advantages and disadvantages of permanent mould casting

Permanent mould casting is a process that makes use of a reusable metal mould made from metal. This process involves pouring molten metal into a mould where cools and solidifies after that mould is opened, casting is removed and mould is reused. Let us have a deep insight into the advantages and disadvantages provided by using this casting process. 

Advantages of permanent mould casting : 

• Close dimensional tolerance can be obtained. 
• This process is economical for large scale production as the labour involved in the mould preparation is reduced. 
• Produce a very good surface finish of the order of 4 microns.
• Better appearance.
• This process produces a fine-grained casting with superior mechanical properties because of the metallic mould used.
• Small cored holes may be produced as compared to sand casting.
• Inserts can be readily cast in place. 
• Increases repeatability of casting.
• A finer grain structure can be obtained.
• High volume production runs.
• Less expensive than investment and die casting.

Disadvantages of permanent mould casting :

• Only non-ferrous metals may be cast by this process.
• Less competitive with sand casting when three or more sand cores are required. 
• Higher tooling cost.
• The complicated shape can not be produced. 
• Only suitable for large scale production. 

Explore more information:

1. Advantages and Disadvantages of Shell mould casting
2. Advantages and Disadvantages of Investment casting
3. Advantages and Disadvantages of Sand casting
4. Advantages and Disadvantages of Die casting
5. Advantages and Disadvantages of Centrifugal casting

Advantages and disadvantages of CNG

CNG stated as compressed natural gas is a fuel used in place of petrol, and diesel fuel It produces fewer undesirable gases in the combustion process than petrol and diesel. Let us have a deep insight into the pros and cons of CNG in this article. 

Advantages of CNG: 

• Less Harmful than coal or oil and environmentally friendly.
• Easy storage and transport because natural gas stored and transported through pipelines, small storage units, cylinders or tankers on land and sea.
• The vehicles operating on CNG has lower maintenance costs as compared to hydrocarbon fuel-powered vehicles so reduced fuel cost.
• CNG gives a better life to lubricating oils, as it does not contaminate and dilute the crankcase oil.
• It produces less pollution in the form of CO2, CO, NOx and SOx as compared to petrol.
• It is lighter than air and tends to dissipate when there is a leakage unlike Propane, which is heavier than air, collects into explosive pockets.
• Using CNG makes the engine cleaner and more efficient.
• Reduced maintenance cost.
• CNG has higher octane levels averaging over 120 octane.
• CNG is abundant in the U.S The country has extensive natural gas resources and a well-established network of pipelines. 
• Switching to CNG can help ease the country's dependence to foreign oil.

Disadvantages of CNG:

• Reduced power for the same engine capacity.
• CNG filling stations are very limited.
• The performance of the car is reduced significantly. 
• Acceleration is slower so you may have to rev the engine more to get going.
• The burning of natural gas also releases carbon dioxide, carbon monoxide and other carbon components which are greenhouse gases that cause global warming.
• Provide less mileage than gasoline.
• Leaks of natural gas are dangerous they may cause explosions or fire. the main danger is that the odourless and leaks cannot be detached unless some odorant has been added to the gas.
• Conversion kits tend to come with a high cost typically it would only make financial sense to convert a late model vehicle to CNG because of the conversion cost.
• Storage space is a very big issue because CNG tanks are large in size so boot space is reduced.
• Cars with CNG kits should always be started on petrol and run for a few kilometres before being switched to the green fuel. This warms up the engine better and gets the motor well lubricated. This cause the injectors to crust and get blocked.
• Non-renewable energy source.
• Natural gas is a source of violence and terrorism.
• Natural gas emits some quantities of greenhouse gas.

Explore more information: 

1. Difference between LPG and CNG

Advantages and disadvantages of fuel injection system

Fuel-injection system is the most vital component in the working of CI engines. The injection system has to perform the important duty of initiating and controlling the combustion process. The injection system main purpose is to the preparation of the combustible charge and is the same as carburetion. Let us have a deep insight into the pros and cons of the fuel injection system. 

Advantages of fuel injection system :

• Setup is simple for a fuel injection system.
• The use of different sensors for detection of various changes such as altitude, throttle position, weather condition would correct the amount of fuel to be delivered to the cylinders.  This maximizes the economy and engine's power.
• Easier to start especially during the harsh winter season.
• Precise, constant and accurate supplication of fuel to the engine.
• Accurate throttle response and tuning options.
• No requirement of adjusting them in accordance with situations.
• Saves undue fuel consumption.  
• Fuel burns efficiently because it becomes atomized as it passes through the cylinder.
• No need for frequent tune-ups in the use of a fuel injection system.
• Ability to run higher compression ratios when the fuel is injected. 
• The vehicle picks up will be good and fast.

Disadvantages of a fuel injection system :

• With the use of an electronic fuel injector, you cannot use leaded gas.
• This system usually has a shortened life unlike with carburettors.
• The fuel injection system is a lot more expensive than a carburettor upgrade.
• Repairing fuel injectors is not easy as compared with carburettors.
• The Air fuel ratio and mix of that will be excellent in a carburettor than a direct Injection system.
• There may be more unburnt hydrocarbon.
• The air-fuel ratio and mix of that will be excellent in a carburettor than a direct Injection system.
• There may be more unburnt hydrocarbon.
• Servicing the fuel injector unit is cumbersome.
• If there is an ECU failure, the bike will seize to work.
• Procuring new fuel maps is a costly affair.
• The need for fuel return lines to the tank in use, or a separate header tank.
• Possible vapour lock in the steel fuel lines above the engine, making it difficult to start a hot engine.

Explore more information: 

1. Types of a fuel injection system

Advantages and disadvantages of disc brakes

A disc brake is a type of brake that uses callipers to squeeze pairs of pads against a disc to create friction that slows the rotation of a shaft, either to reduce its rotational speed or to hold it stationary. One of the biggest advantages is that it can generate and transfer greater amounts of heat to the atmosphere because most of the friction area of a rotor is exposed to air so cooling is faster than drum brake makes them better suited for high-performance driving or heavy-duty vehicles. Let us have a deep insight into the pros and cons of disc brakes to know more about it. 

Advantages of disc brakes :

• Disc brakes require less effort to stop the vehicle.
• It generates less heat.
• The disk brake is simple to install and service.
• The disk brake is easy to control.
• Disk brake can never become self-locking.
• Disk brake has high torque transmitting capacity in a small volume.
• In the disk brake, the braking torque is linearly proportional to the actuating force.
• The disk brake is equally effective for both directions of rotation of the disk.
• Disc brakes will keep working after you bent your rim.
• Disc brake doesn't wear down the rims.
• Disc brakes are that the wheels must be built strongly and they must be able to take high torque stresses between the rim and the hub.
• It is less likely to skid in wet condition. 
• Disc brakes increase the aesthetic value of your bike. 

Disadvantages of disc brakes : 

• A disc brake is much more prone to noise so timely service required. 
• The rotors wrap easier than the drum brake system. 
• Disc brakes are not self-energizing thus need higher clamping forces, which requires a power booster. 
• Expensive as compared to a drum brake. 
• Too many components used in this brake so increases weight. 

Explore more information: 

1. Difference between a drum and disc brakes
2. Types of brakes
3. Mechanical Vs Hydraulic disc brakes

Advantages and disadvantages of automatic transmission system

The automatic transmission also referred to as full auto gearbox is a completely automated gearbox that self-changes gear ratios as the vehicle moves. It uses three main components such as fluid or hydraulic coupling, planetary gear train and hydraulic controls. A fluid coupling did a quite similar job that what a clutch does in a manual gearbox, which changes gear by locking and unlocking a system of planetary gears that provide the various gear ratios. Hydraulic control acts quite similar to fluid coupling but it is typically a gear pump mounted between the torque converter and the planetary gear and controls the clutches depending on the speed of vehicle running condition. Now let us have a deep insight into the pros and cons gives by the automatic transmission system.

Advantages of automatic transmission system : 

• This system gives great driving pleasure. 
• The reduced effort of the driver and more features available to the driver to handle the car. 
• Better for hilly areas. 
• Greatly reduced the risk of stalling.
• Easier to use especially in heavy traffic. 
• Accurate and effortless shifting of gears.
• No clutch replacement cost. 
• To help accelerate quickly. 

Disadvantages of automatic transmissions system : 

• Expensive gearbox thus not equipped with low car price and the initial cost is high.
• A fully automatic gearbox means complexity. 
• Less fuel-efficient because of a lack of control on the torque converter. 
• Maintainance is costly. 
• The additional gear train is required for the reverse condition.  
• Fuel consumption is also higher than a manual transmission. Automatic transmission consumes 10% more than a manual transmission. 
• Take a longer time to change gear between high and low.
• Compromise with the mileage.
• Mechanical efficiency is less.
• Limited torque capacity.
• It may not be best suited for off-road driving.
• Transmission fluid must be transferred every 50,000 km on average.

Explore more information: 

1. Automated manual transmission - Advantages and Disadvantages
2. Dual-clutch transmission - Advantages and Disadvantages
3. Continuous variable transmission - Advantages and Disadvantages

Difference between capstan and turret lathe

Capstan and Turret lathes are the advancements of the Engine lathes and centre lathes in which the tailstock is replaced by a hexagonal turret tool head with 6 different tools in the turret where the turret tool is rotated according to process requirements in each operation. The capstan and turret lathe although appear to be identical at the first sight but a lot of differences in construction, operation, and use. In this article, you can check it out some difference between these two lathe machines. 

Capstan lathe :

• Lightweight machine.
• These are usually horizontal lathe. 
• Turret head is mounted on a slide called ram which is mounted on the saddle.
• Suitable for bar work.
• The saddle is locked at a particular point and the ram is moved to provide feed to the tool.
• Only a limited amount of feed and depth of cut is provided for machining.
• The cross slide is mounted on a carriage that rests on bed ways between the headstock and the ram.
• The turret tool head is indexed automatically.
• Feed stop screws are used to control the distance of tool movement which is at the rear side of the turret.
• No such facility for moving turret at right angles.
• Feed rod gives for longitudinal feed.
• Used for mass production of small size equal part.
• It has hand-operated collet chucks.
• Heavy cuts on the workpiece can't be given because of non-rigid construction. 

Turret lathe :

• Heavyweight machine.
• Turret tool head is directly fitted on the saddle and both of them appear like one unit.
• Suitable for heavier chucking work.
• The saddle is moved to provide feed to the tool.
• They are heavy and durable.
• More feed and depth of cut are provided for machining.
• Some turret type lathes are equipped with side hung type carriage.
• To index the turret tool head, a clamping lever is released and the turret is rotated manually.
• Limit dogs are used to control the distance of tool movement.
• Some turret lathes have the facility of moving the turret at right angles to the lathe axis.
• Feed rod does not give for longitudinal feed.
• Used for mass production of large size equal part.
• It is accommodated with power chucks.
• Heavy cuts on a workpiece can be given because of the rigid construction of a machine. 
• These are available in the horizontal and vertical lathe. 

Related posts: 

1. Difference between capstan turret and engine lathe 
2. What is a lathe machine? Detailed information

Press forging advantages and disadvantages

Press forging defined as the process of shaping a metal that is placed between two dies by applying mechanical or hydraulic pressure. so now let us understand the key pros and cons of press forging to understand more about it. 

Advantages of press forging :  

• It deforms the workpiece completely. 
• The compression rate of the workpiece can be controlled automatically. 
• More economical for high volume productions. 
• Any size and shape can be created. 
• Requires less draft and produces lesser scrap so better dimensional accuracy. 
• Greater accuracy in terms of tolerance within 0.01 to 0.02 inch. 
• This operation is completed in a single squeezing so save time. 
• The plastic deformation goes deep into the centre of the workpiece provides uniform deformation. 
• The capacity of presses ranging from 500 to 9000 tons and the number of working strokes per minute can be high as 40 or even 50. 
• It is suitable for the mass production of nuts, bolts, rivets, screws, brake levers, valves.

Disadvantages of press forging : 

• The initial cost is higher because the cost of the crank press is always higher than of an equivalent hammer. 
• The difficulty of descaling the blank. 
• It is economical when the equipment is efficiently utilized. 

Explore more information:

1. Advantages and disadvantages of Drop forging
2. What is forging? Detailed information
3. Difference between open die and closed die forging

Drop forging advantages and disadvantages

Drop forging is a process that using the die with high strength, a metal blank on forging press will be plastic-deformed, then we will obtain the required shape, size, and internal quality. Now let us discuss the pros and cons of drop forging to understand more about it. 

Advantages of drop forging : 

• The production efficiency is higher. 
• Complex shaped metal parts can be forged with this process, and the distribution of metal flow line is more reasonable. 
• Improve the serving life of parts. 
• Achieve better surface quality, and smaller machining allowance and the size of this process is accurate. 
• Reduce machining work so save metal. 
• It will reduce the cost of spare parts. 
• The production operation is easy, so force or work is low. 
• Improved microstructure. 
• Finer grain size. 
• Continuous grain flow. 

Disadvantages of drop forging : 

• For short runs, this process is not very economical due to the high cost of die production.
• Drop forging presents a dangerous working environment.

Explore more information:

1. Advantages and Disadvantages of Closed die forging
2. Advantages and Disadvantages of Open die forging

Difference between drop forging and press forging

Drop forging is when half of the die is dropped from a height onto the other half of the die, that will contain the hot metal workpiece to be formed and is more suitable for mass production. Press forging is instead of dropping half the die onto the other half the two halves are put together and pushed together under a large pressure to forming the object. 

Main difference : 

The difference is that drop forming leaves the center of the metal not so hard as the outside, but the press forming gives more uniform hardness for larger components. We could also differ forgings from its temperature, such forgings are named cold forging, warm forging, and hot forging. 

Difference :

• The metal is shaped by means of a series of blows in drop forging while in press forging, the metal is shaped by means of a single, continuous stroke. 
• The pressure applied is impacted, and in multi-stroke in drop forging, while the pressure applied is slow, steady and continuous in a single squeezing action in case of press forging. 
• The deformation of metal is more at the surface layers than that of a center of the metal in case of drop forging, while it is uniform, simultaneous and deep penetrating at the center of the metal part. 
• The jarred impressions are obtained in drop forging while impressions obtained in press forging are clean. 
• The draft angles used are more in case of drop forging than that of press forging. 
• Tong holds are normally required for manipulating dies in drop forging whereas in press forging tong holds are not required. 
• The initial cost of drop forging is less as compared to press forging. 
• The drop forging is suitable for almost all types of medium size forgings and press forging is recommended when machine utilization is quite high. 
• The drop forging is a relatively slow process and has moderate production rates where press forging is a faster and higher production rate. 

Closed die forging application

Due to its high precision, closed die forging is preferred for small critical parts with consideration for safety. It is mainly used to produce small products like forged fittings, forged lifting and rigging hardware, forged automotive parts, etc. Now let we check the applications of closed die forging one by one below. 

Applications of closed die forging : 

• According to the advantages of closed die forging, it has become the main metal forming process in modern manufacturing. It can be used for lots of metal components for cars, aeroplane, heavy trucks, shipbuilding, etc. 
• The motivation that encourages many manufacturers to change the production process into closed die forging because it offers better surface finish with good quality, also the price is competitive so we could use this process in below application. 

Automotive application: Connecting rod, control arm, rock arm, axle shafts, axle beams, axle arms, steering yokes. 

Construction machinery applications: Bucket teeth, excavator. 

Agriculture applications: Shafts, spike harrow teeth, tie rod ends, gears. 

Oilfield applications: Elbow, hammer union nuts, cross, tee. 

Mining applications: Ground foundation and auger bits. 

Open die forging application

The differences between open and closed forging process make the end product look different and the major difference in application lies in the size of the product. Now let we understand and applications of open die forging.

Applications : 

• It is the rough process of forging as it does not involve a fixed die size so this process does not use in precision. 
• This process is best suited for forging bigger and heavier metal parts like forged shafts and rollers that find their application in railways because not required much surface finishing machining and create ultra-finished products. 
• The advantages of this process range from better microstructure as the grain size are fine and have a continuous flow this the products in forging method include forged long shafts, forged rollers, and forged cylinders which mostly used for the application of many industries. 

Closed die forging advantages and disadvantages

When it comes to shaping a metal part, forging is the one used to shape the metal in a controlled manner using plastic deformation while there are different types of forging methods, one of the most common is closed die forging. This technique involves the pressing of hot round bars and their net shaping in closed dies. This process provides the desired shapes and is being wide applications for all industries, including engineering, construction, aerospace, power generation, defence, oil, and gas, etc. Let us now have a look at some of its major pros and cons to understand more about it.

Advantages of closed die forging :

• The forging process of closed die creates net shapes or near-net shapes. 
• This process offers superior mechanical properties, higher product strength, and toughness.
• Closed tolerance can be achieved through this process close to + / - 0.3 mm. 
• It is suitable for steel brass and aluminium as well as some other alloys too. Thus, no material limitation. 
• Better surface finish so saves the cost of machining. 
• It is a cleaner and greener process as compared to casting so it is environmentally protected. 
• Good reproducibility and high production rate. 
• Parts of sizes up to 25 tons can be produced. 

Disadvantages of closed die forging :

• This process involves a higher tolling cost that makes it expensive. However, it can be suitable for mass production. 
• Closed die forging may not be helpful for complex and large products.
• This process has a limitation on dimension. 

Thus, this process is overall a cost-effective process when used for mass production and to gain higher product strength and toughness.

Advantages and disadvantages of open die forging

Open die forging is only suitable for simple shapes for its less dimensional accuracy, and high skill operators are required, the dies of this process are simple and less expensive which is the simplest process of all the forging process. In this article, you can check it out the pros and cons of open die forging to understand more about it. 

Advantages of open die forging : 

• Better fatigue resistance and improved microstructure.
• A continuous flow of grain and finer size of the grain.
• Increased strength and prolonged part life.
• Less material waste.
• Reduced chance of voids.
• Cost savings are valuable.

Disadvantages of open die forging : 

• Close tolerance and higher precision parts cannot be formed.
• To achieve the desired dimensions, machining is often required.

Explore more informaion:

1. Advantages and disadvantages of Press forging

Difference between open die forging and closed die forging

The method of deforming a piece of metal between various dies that does not fully enclose the material is open die forging. The metal is modified by a sequence of movements as the dies "hammer" or "stamp" material until the required shape is achieved. 

Let us have a deep insight into the difference between open and closed die forging.

Difference between open and closed die forging : 

• Open die forging is also known as free forging, meaning metal billets compressed under the external compressive force and deformed to desired dimensions in a freeway without forging dies while closed die forging is also known as impression die forging, is a process that heated by medium frequency induction heating furnace to high temperature and forced between upper and lower dies to get expected shapes like the drawing.
• Both forging processes are also different in the side of their processes. Moulding dies are firstly made for closed die forging, and then forged steel bars are placed on the dies and drop forged to desired shapes. In open-die forging, it involves enormous compressive force imposed by the continuous strike of a hammer to make the metal billets deformed. 
• Open die forging will require further rough machining due to its free forging and imprecise dimensions may be reached by second precision machining while closed die forging is more common in small parts for its high precision used to make forged fittings, forged flange and forged automotive parts. 
• The open die metal forged parts are more suitable for larger parts in a number of tons whereas for small parts closed die forging is preferred as high precision is obtained in closed die forging. 

Difference between hot rolling and cold rolling

One of the important processes in metal manufacturing is rolling, but there are two methods available for rolling one is hot rolling and another is cold rolling. It is a common misconception that these processes relate to a specification of metal or grade of metal instead, they refer to how metal is processed at the mill. Now in this article, you can check it out the hot rolling vs cold rolling and some key difference between them. 

What is hot rolling?

Hot rolling is the process in which rolling the steel at a high temperature which is higher than the recrystallization temperature of steel.

What is cold rolling?

Cold rolling is a similar process to hot rolling, the steel is subjected to further cooling process at room temperature in cold reduction mills after being rolled. 

Main difference :

The main difference between these two processes is the temperature in which they are performed. Hot rolling is under high temperature also called as above recrystallization and the cold rolling is under room temperature also called as below recrystallization. 

Some more difference between hot and cold rolling process is explaining below. 

• Hot rolling is the father of cold rolling which follows hot rolling. 
• Hot-rolled metal does not show work hardening effect whereas it shows in cold roller metal. 
• Co-efficient of friction between two rolls is higher in hot rolling it may even cause shearing of metal in contact with rolls and co-efficient of friction us lower in cold rolling. 
• Experiment measurement is difficult in hot rolling while it can be carried out easily in cold rolling.
• Heavy reduction area of a workpiece can be obtained in hot rolling whereas heavy reduction is not possible in cold rolling. 
• The radius of rolls is generally higher for hot rolling and it relatively smaller in cold rolling. 
• The very thin section is not obtained by a hot rolling process vice versa in the cold rolling process. 
• Hot rolling does not allow partial buckling of cross-section while cold rolling is allowed to have local buckling. 
• Mechanical properties are improved by beaking cast structure thus toughness increases in hot rolling and cold rolling increases the tensile strength and yield strength. 
• The hot-rolled surface is not good it has metal oxide on it while the cold-rolled surface is smooth and oxide-free. 

Positive caster Vs Negative caster

Positive caster is when the steering axis is in front of the verticle axis and negative caster is when the steering axis is behind the verticle axis. In this article, you have to clear your mind to check it out the difference between positive and negative caster, comparison and much more details about them.  

Difference : 

• Positive caster occurs when the axis of the steering wheel is ahead of the vertical axis and negative caster occurs when the axis of the steering wheel is behind the vertical axis.  
• A significant amount of positive caster provided that your vehicle has a well-fitted power steering system while negative caster symptoms make the steering wheel light and increasing the susceptibility of your vehicle, and make its path accurate without proper direction.
• Positive caster angles run between 3 - 5° on modern vehicles gives a good mix of highway stability and steering feel. Negative caster is opposite to positive caster. 

Summary : 

If you modify the caster settings on your vehicle, make sure that you keep the angular degrees of the casters completely symmetrical with one another. If you make the mistake of miscalculating the angles of the casters on various wheels of your vehicle, then you will find your car will start pulling more towards one side with respect to another side which doesn't have much of a caster angle. 

Difference between caster and camber

Definition of caster angle : 

The caster angle is the angular displacement of the steering axis from the vertical axis of a steered wheel in a car, motorcycle, bicycle measured in the longitudinal direction. In other words, it is the angle between the pivot line and vertical. 

Definition of camber angle : 

The camber angle is the angle made by the wheels of a vehicle, it is the angle between the vertical axis of the wheels used for steering and the vertical axis of the vehicle when measured from the front or rear. 

Camber angle is taken care of when designing the steering and suspension.

If the top of the wheel is farther out than the bottom, is called positive camber. If the bottom of the wheel is farther out than the top, is called the negative camber. 

This article is about the caster vs camber, what is caster angle, what is camber angle and the comparison between caster and camber.

Difference between the caster and camber : 

• Caster is the angle between the verticle line and kingpin centre line in the plane of the wheel when the view from the side is called the caster angle. Camber is the angle between the centre line of the tyre and the vertical line viewed from the front of the vehicle is known as the camber angle.
• Caster is the steering angle with respect to the wheel's centre and camber is the wheel's angle with respect to its centre. 

Explore more information: 

1. What is a caster?
2. What are toe-in and toe-out?
3. Difference between understeer and oversteer

How to adjust correct steering angle?

The perfect steering is achieved when all the four wheels are rolling perfectly under all running condition. While taking turns, the perfect rolling condition is satisfied if the axis of the front wheels when produced meet the rear wheel axis at one point. Then this point is called the instantaneous centre of the vehicle. 

It can observe that the inside wheel is required to turn through a greater angle than the outer wheel. The larger the steering angle, the smaller the circle of turning. However, a maximum to which we can go as the steering angle. 

It has been found that steering angle can have a maximum value of about 44 degrees. 

The extreme positions are called lock positions on either side. The diameter of the smallest circle which the outer front wheel of the car can traverse and get when the wheels are at their extreme positions is referred to as the turning circle.

Now let we discuss the formula for correct steering angle. 

Correct Steering Angle

Let the axis of the inner wheels makes a larger angle θ than the angle φ subtended by the axis of an outer wheel. 

Let a = wheel track
b =  wheelbase
c = distance between the pivots A and B of the front axle

From the triangle IBP 

cotθ = BP / IP 

From the triangle IAP

cotø = AP / IP = AB + BP / IP = AB / IP + BP / IP = c / b + cotθ

cotø - cotθ = c / b 

This is the fundamental equation for correct steering. 

Explore more information: 

1. What is a caster?
2. Difference between the caster and camber

What is Toe in and Toe out | Definition | Effect

Definition : 

Toe-in is the amount by which the front wheels are mounted closer together on the front than on the back when the vehicle is stationary and viewed from the top. The wheel can be set closer to the rear than to the front, in which case the difference of the distances between the front and rear wheels is called toe-out. 

Effect : 

In rear-wheel-drive vehicles, there is usually an inherent tendency for the wheels to toe-out due to purposeful deviation from centre point steering due to errors in the steering angles of the inner and outer bends of the wheels. 

There is usually an inherent tendency for the wheels to toe-out in rear-wheel drive vehicles just because of purposeful deviation from centre point steering due to errors in steering angles of the inner and outer wheels bends. In order to compensate for this tendency, a small amount of toe-in was initially provided in such vehicles so that the wheels move perfectly straight ahead under normal turning condition. However, the initial toe-out was provided in the case of some front-wheel-drive vehicles to counter the toe-in present therein. 

In rear-wheel-drive vehicles, due to errors in the steering angles of the inner and outer bends of the wheels, there is usually an inherent tendency for the wheels to toe out. 

In rear-wheel-drive vehicles, there is usually an inherent tendency for the wheels to toe out due to purposeful deviation from centre point steering due to errors in the steering angles of the inner and outer bends of the wheels. A small amount of toe-in was initially provided in such vehicles to compensate for this tendency so that the wheels move perfectly straight ahead under the normal turning conditions. 

Toe-in generally does not exceed 3 mm. 

A toe-in wheel alignment can help to reduce oversteer problems and increase stability in front-wheel drives vehicles. 

A toe-out alignment can help to mitigate issues related to understeering and can improve the handling of a vehicle that has rear-wheel drive. 

Explore more information: 

1. What is a caster?

What is caster | Definition | Effect

Definition : 

The caster angle is called the angle between the kingpin centre line for the steering axis and the vertical in the wheel plane. 

If the centre line of the kingpin meets the ground at a point ahead of the verticle wheel centre line is called the positive caster and if it is behind the verticle wheel centre line is called the negative caster. 

Effect : 

The steering axis pulls the front tires, while the tire drag due to the weight of the vehicle is on the vertical line in the centre of the footprint. Since the positive caster steering axis would meet the ground ahead of the tire print centre, the later would always follow former, thus positive caster provides directional stability on the car wheels. 

A positive caster increases the effort required to turn the steering wheel. In the case of negative caster steering, it may be noted that it would be unstable. Example -There would be poor directional control, as in this case the centre of the tire print leads the steering axis. Extremely negative casters would cause shimmy and consequently cupped wear of the front tires. 

As the change of caster angle, the other angles of the steering geometry, the chamber, the inclination of the kingpin and the toe0in or toe-out are changed. Therefore, it is very important that this angle is adjusted first of all while doing the adjustment job. 

Approximately 3 degrees of castor gives good results. 

Explore more information:

1. Difference between caster and camber