The wheel size for a
motor vehicle
A motor vehicle, also known as motorized vehicle or automotive vehicle, is a self-propelled land vehicle, commonly wheeled, that does not operate on Track (rail transport), rails (such as trains or trams) and is used for the transportation of pe ...
or similar
wheel
A wheel is a circular component that is intended to rotate on an axle Bearing (mechanical), bearing. The wheel is one of the key components of the wheel and axle which is one of the Simple machine, six simple machines. Wheels, in conjunction wi ...
has a number of parameters.
Units
The millimetre is most commonly used to specify dimensions in modern production, but marketing of wheel sizes towards customers is still sometimes done with traditional systems. For example, wheels for
road bicycle
The term road bicycle is used to describe bicycles built for traveling at speed on paved roads. Some sources use the term to mean racing bicycle. Other sources specifically exclude racing bicycles from the definition, using the term to mean a ...
s are often referred to as 700C, when they actually measure 622 mm. Wheel diameters and widths for cars are stated in
inch
Measuring tape with inches
The inch (symbol: in or ″) is a unit of length in the British imperial and the United States customary systems of measurement. It is equal to yard or of a foot. Derived from the Roman uncia ("twelfth") ...
es, while car tire bead diameters are stated in inches and widths are in millimetres.
Wheel size
200px, Wheels with Asanti rims on a police car">Hummer H2 car
The ''wheel size'' is the size designation of a wheel given by its diameter, width, and offset.
The
diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for ...
of the wheel is the diameter of the cylindrical surface on which the tire bead rides. The width is the inside distance between the bead seat faces. The offset is the distance from the wheel's true centerline (half the width) to the wheel's mounting surface. Offset is covered in more detail below. A typical wheel size will be listed beginning with the diameter, then the width, and lastly the offset (+ or - for positive or negative). Although wheel sizes are marketed with measurements in inches, the
Michelin TRX The Michelin TRX, (and the related TDX), is a radial tire introduced by the Michelin Group in 1975. It is one of the first volume-produced low-profile tires. Although technologically advanced, and reasonably successful, the tire's requirement for a ...
introduced in 1975 was marketed in millimeters.
For example, 17 × 8.5 × +35 designates a diameter of 17 inches, width of 8.5 inches, and +35 mm positive offset (432 × 216 × +35 in fully metric numbers).
Replacing the wheels on a car with larger ones can involve using tires with a lower profile. This is done to keep the overall diameter of the tire the same as stock to ensure the same clearances are achieved. Larger wheels are typically desired for their appearance but could also offer more space for brake components. This can come at cost of performance though as larger wheels can weigh more.
Alternatively, smaller wheels are chosen to fit a specific style of vehicle. An example of this is the
Lowrider
A lowrider or low rider is a customized car with a lowered body. These customized vehicles are generally individually painted with intricate, colorful designs, rolling on wire-spoke wheels with whitewall tires. Lowrider rims are generally smalle ...
Culture in which smaller wheels are largely desired.
Wheels can be widened to allow for a wider tire to be used and to poke the wheel out to the fender of the vehicle. Running a wider tire allows for more of the vehicle's power to be put to the ground because there is a larger
surface area
The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc ...
making contact with the road. This will improve a vehicle's performance when it comes to
acceleration
In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by the ...
,
handling, and
braking
A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction.
Background ...
.
Bolt pattern
![The tire wheel of Subaru BRZ S (DBA-ZC6) with optional parts](https://upload.wikimedia.org/wikipedia/commons/c/ce/The_tire_wheel_of_Subaru_BRZ_S_%28DBA-ZC6%29_with_optional_parts.jpg)
The ''bolt pattern'' determines the number and position of the bolt holes on the wheel to line up with your vehicle's studs on the mounting hubs. The bolt holes are spaced evenly about the
bolt hole circle. ''Wheel studs'' are the bolts that are on your mounting hub and are used along with lug nuts to attach the wheel to the car. The ''bolt hole circle'' is the circle that the center of each bolt aligns with. The second number in a bolt pattern is the diameter of this circle. The bolt circle has the same center point as the mounting hub to ensure that the wheel will be
concentric
In geometry, two or more objects are said to be concentric, coaxal, or coaxial when they share the same center or axis. Circles, regular polygons and regular polyhedra, and spheres may be concentric to one another (sharing the same center point ...
with the mounting hub. The bolt circle's measurement is called the bolt circle
diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for ...
(BCD), also called the ''pitch circle diameter'' (PCD).
The bolt circle diameter is typically expressed in ''mm'' and accompanies the number of bolts in your vehicle's bolt pattern. One example of a common bolt pattern is 5x100 mm. This means there are 5 bolts evenly spaced about a 100 mm bolt circle.
The picture to the right is an example of
5×100 mm bolt patternon a Subaru BRZ. The wheel has 5 lug nuts and utilizes a 100 mm bolt circle diameter.
5hole_wheel.png, 5-hole bolt pattern
4hole_wheel.png, 4-hole bolt pattern
Some of the most common BCD values are 100 mm (≈3.94 inches), 112 mm (≈4.41 inches), and 114.3 mm (4.5 inches). Always check your owner's manual or call your local car dealership to confirm the bolt pattern on your vehicle. Over the years, over 30 different bolt patterns have been used by car manufacturers,
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/ref> with most of the different bolt patterns being incompatible with each other.
Lug nuts and wheel studs vs. bolts
On vehicles with wheel stud
Wheel studs are the threaded fasteners that hold on the wheels of many automobiles. They are semi-permanently mounted directly to the vehicle hub, usually through the brake drum or brake disk. Lug nuts are fastened onto the wheel stud to secure ...
s, wheels must be fitted with the correct type of lug nut
A lug nut or wheel nut is a fastener, specifically a nut, used to secure a wheel on a vehicle. Typically, lug nuts are found on automobiles, trucks (lorries), and other large vehicles using rubber tires.
Design
A lug nut is a nut fastener wi ...
s. On vehicles without wheel studs, wheels must be fitted with the correct type of lug bolt
A lug nut or wheel nut is a fastener, specifically a nut, used to secure a wheel on a vehicle. Typically, lug nuts are found on automobiles, trucks (lorries), and other large vehicles using rubber tires.
Design
A lug nut is a nut fastener ...
s.
Lug nuts (or bolts) will have either flat, tapered (conical), or ball (radius) seats. The type of seat a wheel requires will determine the appropriate lug nuts required to securely attach the wheel to the vehicle. A flat seat type has a flat end that puts pressure on the wheel and compress it against the mounting hub. Similarly, tapered and ball seat types have a conical or semicircular end, respectively. A place to find the lug nut type is to check OEM (Original Equipment Manufacturer) specifications if you have stock wheels or contact the wheel manufacturer if you have aftermarket wheels.
Some aftermarket wheels will only fit smaller lug nuts, or not allow an ordinary lug nut to be properly torqued down because a socket will not fit into the lug hole. Tuner lug nuts were created to solve this problem by utilizing a special key to allow removal and installation with standard lug wrench or socket. The design of tuner lug nuts can range from bit style to multisided or spline drive, and are sometimes lightweight for performance purposes.
Another variation of lug nut is the "locking wheel nut", which is used as a theft prevention method to keep thieves from stealing a vehicle's wheels. When utilizing locking wheel nuts, one standard lug nut on each wheel is replaced with a nut that requires a unique key (typically a computer-designed, rounded star shape) to fit and remove the nut. This ensures that at least one lug nut will remain attached and, in theory, should prevent theft. However, universal removal tools are available which grip the head of the locking nut using a hardened left-hand thread. The success of locking wheel nuts depends on the determination of the would-be thief and the tools that they have available to them.
Andreas Mikkelsen's Car at Service in Gap (4), Rallye Monte-Carlo 2019.jpg, Car with five wheel studs for use with lug nuts
TSM350 - 2015 - Stierch 19.jpg, Five yellow lug nuts for use on a car with wheels studs
Give me a... yeah, alright. (15694589508).jpg, Car without wheels studs for use with (four) lug bolts
Kugelbundschrauben-92154.jpg, Four lug bolts, from left: Three M12x1.5 mm bolts with different length and one M14x1.5 mm bolt
Offset
The ''offset'' is the distance from the hub-mounting surface to the wheel's true centerline. It is quantified by an ''ET'' value (from the German ''Einpresstiefe'', literally ''press-in depth'') and measured in ''mm''. A positive offset means the hub-mounting surface is closer to the outside edge of the wheel, while a negative offset means the hub-mounting surface is closer to the inside edge of the wheel.
A wheel with too much positive offset will be closer to the edge of the fender. This can cause clearance issues between the tire and the fender. One that has too much negative offset will be closer to the suspension components and could cause the tire to rub on them. Wheel width, offset, and its accompanying tire size all determine how a particular wheel/tire combination will fit on a given vehicle. Offset also affects the scrub radius
The scrub radius is the distance in front view between the king pin axis and the center of the contact patch of the wheel, where both would theoretically touch the road. It can be positive, negative or zero.
The kingpin axis also known as steerin ...
of the steering and it is advisable to stay within the limits allowed by the vehicle manufacturer. Because wheel offset changes the lever-arm length between the center of the tire and the centerline of the steering knuckle, the way bumps, road imperfections, and acceleration/braking forces turn into steering torques (bump-steer, torque-steer, etc.) and thus, will change the drivability of the vehicle depending on wheel offset. Likewise, the wheel bearings will see increased thrust loads if the wheel centerline is moved away from the bearing centerline.
When choosing an offset for an aftermarket wheel, it is important to take note of the space between the outer edge of the wheel and the fender. Depending on the desired style, you may want to match the change in offset from stock wheels to the amount of space between the wheel face and the fender. For example, if there is 15 mm of space between the outer face of the wheel and the fender and you're wanting a flush fitment, you would want to go from a +45 mm offset to a +30 mm offset. This will bring the mounting surface of the wheel further inward towards the vehicle from the true center point of the wheel thus poking the wheel out by an extra 15 mm.
Centerbore
The centerbore of a wheel is the hole in the center of the wheel that centers it over the mounting hub of the car. Some factory wheels have a centerbore that matches exactly with the hub to reduce vibration by keeping the wheel centered. Wheels with the correct centerbore for the car they will be mounted on are known as hubcentric. Hubcentric wheels reduce the job of the lug nuts to center the wheel on the hub. Wheels that are not hubcentric are known as lugcentric, as the job of centering is done by the lug nuts assuming they are properly torqued down. Another, more common, term is hub piloted or stud piloted wheels and hubs. The stud piloted (lug centeric) is an older design while the hub piloted design is more commonly in use today and can provide for a more accurate connection.
Centerbore on aftermarket wheels must be equal to or greater than that of the hub, otherwise the wheel cannot be mounted on the car. Many aftermarket wheels come with "hubcentric rings" that lock or slide into the back of the wheel to adapt a wheel with a larger centerbore to a smaller hub. These adapters are usually made of plastic but also in aluminum. Plastic rings only provide initial centering, but are not strong enough to help support the wheel in case of high-speed pot hole hit. Steel ring is strongest, and aluminum is medium
Brake caliper clearance
The caliper clearance, also called the "X-factor", is the amount of clearance built into the wheel to clear the vehicle’s caliper assembly.
Tire sizes
Modern road tires have several measurements associated with their size as specified by tire code
Automotive tires are described by an alphanumeric tire code (in North American English) or tyre code (in Commonwealth English), which is generally molded into the sidewall of the tire. This code specifies the dimensions of the tire, and some o ...
s like 225/70R14. The first number in the code (e.g., "225") represents the nominal tire width in millimeters
330px, Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The microwave is between 1 meter to 1 millimeter.
The millimetre (American and British English spelling differences#-re, -er, ...
. This is followed by the aspect ratio (e.g.,"70"), which is the height of the sidewall expressed as a percentage of the nominal tire width. "R" stands for radial and relates to the tire construction. The final number in the code (e.g.,"14") is the mating wheel diameter measured in inches. The overall circumference of the tire will increase by increasing any of the tire's specifications. For example, increasing the width of the tire will also increase its circumference, because the sidewall height is a proportional dimension. Increasing the aspect ratio will increase the height of the tire and hence the circumference.
Off-roading
Off-roading is the activity of driving or riding in a vehicle on unpaved surfaces such as sand, gravel, riverbeds, mud, snow, rocks, and other natural terrain. Types of off-roading range in intensity, from leisure drives with unmodified vehicl ...
tires may use a different measurement scheme: , followed by wheel size (all in inches) – for example 31×10.50R15 (787 mm × 267 mm R380 in metric designation). The size of the wheel, however, is denoted as . This means that the width of the wheel is and the diameter is .
Load capacity
Load capacity is the amount of mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...
a wheel will carry. This number will vary depending on the number of lugs, the PCD, the material used and the type of axle the wheel is used on. A wheel used on a free rolling trailer axle will carry more weight than that same wheel used on the drive or steering axle of a vehicle. All wheels will have the load capacity stamped on the back of the wheel. The Gross Vehicle Weight Rating
Vehicle weight is a measurement of wheeled motor vehicles; either an actual measured weight of the vehicle under defined conditions or a gross weight rating for its weight carrying capacity.
Curb or kerb weight
Curb weight (U.S. English) or kerb ...
(GVWR) is the maximum operating mass of a vehicle as specified by the manufacturer. In the United States this information is required to be on the vehicle's door placard. The load capacity of the total number of wheels on the vehicle combined must meet or exceed the vehicle's gross vehicle weight rating.
Staggered wheel fitment
Staggered wheel fitment usually appears on rear-wheel drive vehicles (and in smaller numbers some all wheel drive cars), when the rear wheels are wider than the front wheels. Such a wheel setup may be found on the Ford Mustang
The Ford Mustang is a series of American automobiles manufactured by Ford. In continuous production since 1964, the Mustang is currently the longest-produced Ford car nameplate. Currently in its sixth generation, it is the fifth-best selli ...
, Infiniti G35
The Infiniti G Line is a series of compact executive cars produced by Infiniti, a luxury division of Nissan, for the 1991–1996 and 1999–2016 model years. The first two generations of the Infiniti G (P10 and P11) were sedans based on the Niss ...
, certain models of Mercedes and BMW, etc. A good example of such wheel combination is having in front and in the rear. Technically, wider wheels in the rear allow better grip with the road surface which is a performance benefit for better acceleration.
;Advantages
* Better grip with the road for improved acceleration;
* Better cornering ability;
;Disadvantages
* The rear wheels cannot be rotated to the front and vice versa;
* The front and rear wheels will have different tire sizes;
* In case of improper installation the large rear wheel may rub suspension or wheel arches.
Another setup option of staggered wheel fitment is called double staggered, having smaller diameter narrow width wheels in the front with larger diameter and wider width wheel in the back. For example, a vehicle may feature wheels in front and in the rear. Such setups are found in the Chevrolet Corvette
The Chevrolet Corvette is a two-door, two-passenger luxury sports car manufactured and marketed by Chevrolet since 1953. With eight design generations, noted sequentially from C1 to C8, the Corvette is noted for its performance and distinctive ...
s, the first and second generation of the Acura NSX NSX may refer to:
Stock exchanges
* Namibian Stock Exchange (NSX)
* National Stock Exchange (Jersey City, New Jersey), US (NSX)
* National Stock Exchange of Australia (NSX)
Other uses
* Neon Swing X-perience (NSX), a US musical group
* Honda NSX ( ...
, and some others.
See also
* Plus sizing
Plus sizing is the practice of replacing an automotive wheel with one of a larger diameter fitted with a new tire of lower aspect ratio so that the new tire has close to the same diameter and circumference as the original tire to minimize any cha ...
* Speedometer#Error - handy tire diameter formula, using tire code
Automotive tires are described by an alphanumeric tire code (in North American English) or tyre code (in Commonwealth English), which is generally molded into the sidewall of the tire. This code specifies the dimensions of the tire, and some o ...
* Tire code
Automotive tires are described by an alphanumeric tire code (in North American English) or tyre code (in Commonwealth English), which is generally molded into the sidewall of the tire. This code specifies the dimensions of the tire, and some o ...
* Uniform Tire Quality Grading (UTQG)
Determine Wheel Size
References
{{DEFAULTSORT:Wheel Sizing
Automotive technologies
Mechanical standards
Tires
Automobile wheels