The tire works as a wheel only after it is installed on the rim and is inflated. Therefore, the tire and wheel assembly influences the function and the performance of the vehicle. The tire is designed and manufactured to suit a standard rim and once installed on the correct rim the tire will perform up to its desired level. It is needless to say that the life of the tire will be shortened if it is installed on an unsuitable rim.

The rim is actually the name for the cylindrical part where the tire is installed. A wheel is the name for the combination between the rim and disc plate. Once the disc plate is installed inside the cylinder this assembly becomes a wheel.

1. History of Wheel/Rim

Several thousand years ago was the start of the history of wheel when the human race began to use the log to transport heavy objects. The original of the wheel were the round slices of a log and it was gradually re-inforced and used in this form for centuries on both carts and wagons.

This solid disc changed to a design having several spokes radially arranged to support the outer part of the wheel keeping it equidistant from the wheel centre.

A wooden wheel which used hard wood stakes as spokes was very popular as a wheel for many vehicles up to about 1920.

Afterwards the disc wheel, in which the spokes were replaced with a disc made of steel plate, was introduced and is still being used to this day.

Furthermore, a light alloy has come to be used currently as a wheel material for many types of vehicle.

2. Type of Wheel/Rim (Dimensional)

The rim used for vehicles is provided depending on each countries standard. This international standard, similar to tires, provides for a basic dimension for the rim diameter, width, and the flange shape, etc. and is common to every country in the world. Recently the shape of the rim has settled to 5 degree Drop Center Rim to provide for international harmony.

(1) Shape of Rim

Typical rim shape vehicles are made up of the following three types.

A) Drop Center Rim (DC)

Drop Center Rim (DC Rim) is shaped so there is a well between the bead seat part which is located on both sides of the rim. This well is to make the mounting and dismounting of the tire easy. In most cases there is a taper of 5 degrees in the bead seat area.

B) Wide Drop Center Rim (WDC)

Wide Drop Center Rim (WDC Rim) is basically the same as DC Rim. To expand the width of the rim, with a shallower well and a lower flange height, this rim is mainly applied to low aspect ratio tires. This design is currently applied to rims for tires of most passenger vehicles.

C) Wide Drop Center Rim with hump (WDC)

In addition, this design has a bump, which is called a hump, on the beginning of the bead seat area. This hump is to prevent the bead slipping down and air leakage from the rim due to the horizontal force applied to the tire when a vehicle tubeless tires turns at high speed.

(2) Rim Size Designation

Rim size designation is as below:

(3) Rim Nomenclature

A) Wheel: Wheel is generally composed of rim and disc.

B) Rim: This is a part where the tire is installed.

C) Disc: This is a part of the rim where it is fixed to the axle hub.

D) Offset: This is a distance between wheel mounting surface where it is bolted to hub and the centerline of rim.

E) Flange: The flange is a part of rim which holds the both beads of the tire.

F) Bead Seat: Bead seat comes in contact with the bead face and is a part of rim which holds the tire in a radial direction.

G) Hump: It is bump what was put on the bead seat for the bead to prevent the tire from sliding off the rim while the vehicle is moving.

H) Well: This is a part of rim with depth and width to facilitate tire mounting and removal from the rim.

(4) Rim Width

The width of the rim is provided in TRA, ETRTO, and JIS, etc. according to the size of the tire. Generally rim width difference of about plus/minus one inch is allowed to be used in comparison to the design rim; you should confirm the most suitable rim size for the tire from the tire dealer. The tire manufacturer designs the tire to become the best profile when the tire is mounted on a design width rim. Generally, it is best to use the design width rim to obtain the optimum performance from the tire.

When the car installed with tubeless tires under greatly decreasing the air pressure turns rapidly a large side force is applied to the tire. The bead sometimes drops into the well of the rim, and the air comes out suddenly. This situation is made worse when an overly wide rim is used. If the tire is used on a narrow rim, the stress concentrates on the bead part where it touches the rim and flange. The rubber in this part and the ply cord wear out, and becomes damage which is called Rim Chafing. Moreover, if severe cornering is repeated with the air pressure of the tire lowered, Rim Chafing might occured to the tire.

3. Type of Wheel/Rim (Material)

Steel and light alloy are the main materials used in a wheel however some composite materials including glass-fiber are being used for special wheels.

(1) Wire Spoke Wheel

Wire spoke wheel is a structural where the outside edge part of the wheel (rim) and the axle mounting part are connected by numerous wires called spokes. Today's vehicles with their high horsepower have made this type of wheel construction obsolete. This type of wheel is still used on classic vehicles. Light alloy wheels have developped in recent years,a design to emphasize this spoke effect to satisfy users fashion requirements.

(2) Steel Disc Wheel

This is a rim which processes the steel-made rim and the wheel into one by welding, and it is used mainly for passenger vehicle especially original equipment tires.

(3) Light Alloy Wheel

These wheels based on the use of light metals such as aluminium and magnesium have become popular in the market. This wheel rapidly become popular for the original equipment vehicle in Europe in 1960's and for the replacement tire in United States in 1970's. The features of each light alloy wheel is explained as below;

A) Aluminium Alloy Wheel

Aluminium is a metal with features of excellent lightness, thermal conductivity, corrosion resistance, characteristics of casting, low temperature, machine processing and recycling, etc. This metals main advantage is reduced weight, high accuracy and design choices of the wheel. This metal is usefull for energy conservation because it is possible to re-cyle aluminum easily.

B) Magnesium Alloy Wheel

Magnesium is about 30% lighter than aluminium, and also, excellent as for size stability and impact resistance. However, its use is mainly restricted to racing, which needs the features of lightness and high strength at the expense of corrosion resistance and design choice, etc. compared with aluminium.

Recently, the technology for casting and forging is improved, and the corrosion resistance of magnesium is also improving. This material is receiving special attention due to the renewed interest in energy conservation.

C) Titanium Alloy Wheel

Titanium is an excellent metal for corrosion resistance and strength (about 2.5 times) compared with aluminum, but it is inferior due to machine processing, designing and high cost. It is still in the development stage although there is some use in the field of racing.

D) Composite Material Wheel

The composite materials wheel, is different from the light alloy wheel, and it (Generally, it is thermoplastic resin which contains the glass fiber reinforcement material) is developed mainly for low weight. However, this wheel has insufficient reliability against heat and for strength. Development is continuing.

4. Manufacuturing Method of Wheel/Rim

The steel disk wheel and the light alloy wheel are the most typical installation. The method of manufacturing the light alloy wheel, which has become popular in recent years, is explained here. The manufacturing method for the light alloy wheel is classified into two. They are cast metal or the forged manufacturing methods.

The aluminum alloy wheel is manufactured both ways, and the casting manufacturing method is used as for the magnesium alloy wheel. There are the following three methods of manufacturing the aluminum alloy wheel.

(1) One Piece Rim

This is a method of the casting or the forge at the same time by one as for the rim and disc.

(2) Two Pieces Rim

This is the methods which separately manufacture the rim and disc similar to the manufacture of the steel wheel and these components are welded afterwards.

(3) Three Pieces Rim

This is a method to manufacture each flange separately, and combining later to the disc by welding.

Each method is shown below.

(4) Forging Method (for One Piece Rim)

(5) Forging Method (for Two Pieces Rim)

(6) Forging Method (for Three Pieces Rim)

(7) Casting Method

5. Test of Wheel

Wheels are part of a vehicle and as such subjected to a high load. The durability of the wheel is important for the safe operation of the vehicle. Therefore, it is necessary to examine a wheel for both strength and fatigue resistance.

(1) Endurance Test in Direction of Radius of Rim

The tire on the test rim is rotated under high pressure condition on steel drum and the durability of the rim is examined. Sometimes, test is done giving camber angle and adding a side force.

(2) Test of Disc

The rim flange is tested by applying a load from an arm mounted to the hub. A bending moment is applied while the rim rotates.

(3) Impact Test

The case where the wheel collides with curb of the road or a large obstacle is assumed and the fall impact examination is done.

(4) Others

The test for welding between rim and disc and the nut seat tightening etc. are provided in the vehicle test standard. Moreover, nondestructive testings such as X ray and color check, etc. are adopted to the light alloy wheel to detect the defects in the casting process. Bead Unseating Test, provided in the tire safety standards, for a mounted tire and the rim is also applied.

In addition tests are carried out in the field with the assembly mounted on a vehicle under various road surfaces.

6. Use Limit of Wheel

Though we think it is possible to permanently use a wheel until it rusts away there is a limit to a wheels useful life. If a rim is used in severe operations such as racing or rallying hidden damage is caused. This may result in a an accident or sudden rim failure whilst damage is caused. This may result in a an accident or sudden rim failure whilst the vehicle is in service. The life of a rim is varied according to using conditions. A rim normally lasts longer than a tire so at time of a tire change a rim should be checked for damage or sign of failure. If any are found the rim should be scrapped.

In the case of steel wheel, cracks and corrosions by rust at the joint parts of rim and disc, nut seats, between decoration holes of the rim or the flange is bent, you should scrap the rim.

WARNING

If you install a tire on a different size rim…, you could be dead wrong!!

Although it is possible to pass a 16 inch tire over the lip or flange of a 16.5 inch rim, it cannot be positioned properly.

Rims of different diameters and tapers cannot be interchanged. The diagram below illustrates the difference between rims of two different tapers and diameters.

Every rim includes information on diameter and width. Please always make sure the stamped rim size matches the tire bead diameter. Most wheels include a warning label inside the rim to protect employees who mount tires and wheels.

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1. Some Reasons for High Frequency of Vehicle Vibrations

(1) Lighter Car Weight

Recently car manufacturers have been developing smaller vehicles with lighter body weights under the requirements of energy conservation. Conversely larger sized vehicles have become heavier due to the requirements of safety and many added accessories.

What has changed in all vehicles is the unsprung weight (that is weight not supported by the springs) has become lighter. Lighter unsprung weight results in improved vehicle handling, response and control.

The wheel and axle components are more finely balanced in vehicles with light unsprung weights. This results in any imbalance or vibration of the tire being transmitted through the steering system and being more noticeable in the vehicle.

(For example : When riding in a light vehicle , such as a sports car, you are able to feel any vibration sensitively more readily).

(2) Higher Running Speeds

Tire imbalance vibration problems mainly occur when the vehicle speed is around 100km/h. The high speed stability of vehicles has improved, and the opportunity to drive at higher speeds has increased.

The force of tire imbalance is increased in proportion to the square of the speed. As such, the vehicle speed has a larger influence on vibration levels, especially in modern vehicles.

(3) Lower Profile Tires

A tire absorbs vibrations from the road by the sidewall. Low profile tires have low height sidewalls, which makes absorbing the vibration from the road difficult. Therefore the feeling of vibration is harsher with lower profile tires than with taller profiles.

As an example, when the body of a car is hit by a rubber hammer and a steel hammer with the same force, the difference in vibration is very noticeable.

Due to the above, the adjustment of tire and rim balance becomes more important.

2. Important Points in Balancing Tires

(1) Adjust to Nearly '0' Grams

Many wheel balancers may indicate a minimum of 10 grams. This, however, is not acceptable for tire balancing in recent years. It is necessary that the balance machine indicate a tolerance below 10g. If the wheel imbalance (whether mounting on a vehicle or wheel balancer) equals W1, and if there is nearly 10g tolerance equal to W2, then W1+W2 may be close to (or over) the marginal vibration level.

(2) Use Good Adapters

Using good, well maintained adapters is important, but often these receive little attention. The use of a cone type adapter rear mounted is the better option. The hub centre mounts centric to the wheel centre, and using a cone adapter will give the same condition as when the wheel is mounted on the vehicle, and will minimize the differences in mounting.

(3) Measuring Tire Balance and Run-out

When the tire and rim rotate on a balancer, the pitch (radial run-out) requires noting. If there is a large radial run-out, vibrations will occur when driving. This will require an adjustment by breaking the beads and remounting the tire on the rim. (See below 'Match Mounting Steps'.)

*Match Mounting Steps

(A)	Match the lightest point of the tire (yellow circle) with the valve stem on the wheel as shown below. Adjust the tire-wheel assembly imbalance, thereby reducing the vibrations.
(B)	If the total radial run-out is greater than 1.0 mm, note the high spot on the tire and this spot on the wheel. Also mark a reference point on the tire opposite the valve location.
(C)	Break the tire beads from the rim and rotate the wheel 180 degrees. Re-inflate the tire and check the run-out again.
(D)	If the run-out is still outside the acceptable limit and the high spot is within 100 mm of the first spot of the tire, the tire should be replaced.
(E)	If the high spot is now within 100 mm of the first spot of the wheel, the wheel should be replaced.

(4) Mounting the Wheel on the Vehicle.

Wheels are classified as either "hubcentric" or "lugcentric", with most O.E.M. wheels being the hubcentric type. Hubcentric wheels are easy to centre due to the diameter of the hub hole of the wheel being almost same as the hub hole of the vehicle.

However in case of lugcentric wheels, the diameter of the hub hole of the wheel is larger than the hub hole of the vehicle. (That is the diameter of the lugcentric wheel's hub hole is different from the vehicle's hub hole.) This is why it is difficult to centre the wheels on the vehicle.

Lugcentric wheels come with locating rings for the vehicle hub. These locating rings are designed to fill the gap between the wheel hole and the vehicle hub. Ensure the locating rings are fitted to the vehicle before fitting the wheel. The rings enable the wheel to be centered correctly on the vehicle.

When tightening the wheel nuts, the bolt holes may expand from the lug nut pressure if the nuts are tightened completely using an impact wrench. For this reason the lug nuts should be tightened gently and gradually at first, then finally the nuts should be tightened completely using a torque wrench or torque stem socket adapters.

It is recommended to pay special attention to the above when fitting lugcentric wheels to a vehicle.

The problem of vibrations is becoming more critical. The problem can almost always be solved by using the latest balancer and associated equipment. Maintaining the balancer and associated equipment in good condition by regular maintenance is essential.

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Vibration of vehicles is one of the major problems in the tire business. Our survey made by the technical service staff in the USA and Canada revealed that, as the cause of vibration problem, it seemed that presently many tire dealers were applying lubrication carelessly and excessive lubrication could cause slip between the tire and rim which led a vibration problem.

Example of Excessive Lubrication

Example of Tire-Rim Slip

It is strongly recommend to follow the below procedures;

(1)	For new tire and wheel assemblies, please clean the tire beads of any manufacturing related lubricants with an approved rubber cleaner fluid commonly used in the tire repair process.
(2)	Please clean the wheel bead seating area.
(3)	Please use a sponge and paste-type lubricant to lubricate the tire bead sole according to the photo shown to the below.
(4)	If more than 40 psi is required to seat the beads, please dismount the tire, re-lubricate it and then repeat the process.
(5)	Please index the wheel valve stem to some location on the tire sidewall so that slippage can be confirmed in the event of a customer return for vibration.
(6)	In the event of a customer complaint where tire/ wheel slip has occurred, please remove the old weights and re-balance the assembly. Please do not dismount the tire unless there is a requirement to match-mounting the assembly.

*Warning

European-made alloy wheels may require higher mounting pressure, as bead seat tolerances may be tighter. Additional lubrication of the safety hump (as shown below) may be required to facilitate bead seating.

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There are many causes for the problem of vehicle vibration. Unfortunately, when the problem occurs, the tires are the primary suspected due to their importance to a vehicles satisfactory operation.

In fact, tire vibration has now become one of the most popular complaints for tire quality. From time to time the tire has a problem of poor uniformity, but there are many cases when tires are adjusted for a vibration complaint when there is no defect at all. Nonetheless, we are forced to adjust the tire even when we understand well that the vibration on a vehicle is not always due to the tire. This occurs because we cannot prove that the cause is other than the tire.

From now on, a case study result for the uniformity of tire-rim assembly will be introduced. This analysis shows that the cause of vibration is not merely tire uniformity and the non-uniformity of tire-rim assembly can be dramatically improved by using match mounting method.

1. Analysis Items

(1) Tire Radial Force Variation (RFV)

(2) Rim Radial Run-Out (RRO)

(3) Phase between Tire and Wheel

(4) Tire Fitting to Rim

(5) Rim Centering for Hub of Vehicle

The contribution of these individual items for assembly RFV was measured and analyzed by using an experimental planning method. The contribution of a phase between tire and rim was divided into tire and rim part and be combined with each item.

2. Analysis Results

(1) Share for RFV of Tire-Rim Assembly

A) Better Tire RFV & Rim RRO Combination

B) Worse Tire RFV & Rim RRO Combination

(2) Share for RFV of Tire-Rim Assembly and Effect of Match Mounting

A) Better Tire RFV & Rim RRO Combination

B) Worse Tire RFV & Rim RRO Combination

The worst assembly includes the effect of worse fitting and centering between a tire and a rim. Moreover the peaks of tire RFV and rim RRO were located on the same position, which maximized the level. However, in the case of best assembly, it was minimized.

As shown, tire is not the highest contributor for RFV of tire and rim assembly. Match mounting proves to be very effective. Off course this is just our case study and there may be some variation in the field, but the vibration problem on vehicles is not only caused by the tire.

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