on 25, Oct 2018

Alloy wheels have transformed from an option to a norm in the clear majority of cars we see today. Every other car available today will have the choice of alloy wheels in the top-spec variant along with steel wheels in the base and lower variants. Alloy wheels are omnipresent in today’s automotive culture with steel wheels almost on the verge of extinction. They are 50% lighter than steel wheels with better heat conduction which further helps the wheels dissipate any kind of heat generated from the tires and brakes. The icing on the cake; however, is not the weight savings but the aesthetics associated with a good set of alloy wheels which has the ability to completely transform a sober looking car to an exciting looking car. Read on for some insight into alloy wheels and what makes them so popular today.

TYPES

Alloy wheels are generally made from an alloy of magnesium or aluminium. Alloy, as in boring chemistry terms, is a mixture of a metal and another element. The earliest light alloy wheels were made of Magnesium known as mag wheels. Magnesium has many advantages, but owing to their low ductility, they were later replaced with other elements. Alloy wheels can be mainly classified into two groups based on their production methods.

  1. CAST ALLOY WHEELS

Cast alloy wheels are made from casting process which involves the process of pouring liquid metal into a casting. The liquid metal is then cooled to create solid wheels of requisite dimensions. They are usually made from aluminium alloys. The two prime types of casting are gravity casting and low-pressure casting. Cast alloy wheels are more common and casting methods like gravity casting have been around since the 1920s. They are cheaper than their counterparts but cast alloy wheels tend to be on the heavier side.

  1. FORGED ALLOY WHEELS

Forged alloy wheels are made by forging or sculpturing the one-piece billet (solid metal) with the use of heat and pressure to produce desired shapes and patterns. Aluminum alloys and steel are mainly used in this process. Forged alloy wheels have high tensile strength with lesser weight than cast alloy wheels making them more durable, expensive and a prime choice for racing and motorsport applications. The forging process is extensive and not as rudimentary as the casting process, this coupled with the high-grade alloys used for forged alloy wheels make them dearer than the cast alloy wheels by a substantial margin.

Flow formed wheels or flow forged wheels are also available which is the middle ground between the cast and forged wheels. These wheels begin their life as cast wheels but are loaded into a machine which spins the wheel while pressing steel rollers against the rim to put it into its final shape and width. These kinds of wheels cost between cast and forged wheels with more strength than cast wheels; ultimately striking a balance between both.

The latest innovation in the wheel set is Carbon fibre wheels which can be seen in High-end sports and racing cars. These wheels sit in the apex of the whole alloy-wheel food chain, courtesy of them being the lightest and the strongest wheels. These are the best wheels that money can buy with impeccable strength and extreme lightweight properties. Swedish hypercar giant Koenigsegg offered one-piece carbon fibre wheels in 2013. Today, Porsche, Ford and Ferrari have started using carbon fiber wheels in their flagship models like the 911 Turbo S, GT, Mustang GT350R, and the 488 Pista. What was once only confined to racing cars will be ubiquitous in the supercar/hypercar segment in the near future with carbon fibre being the answer to most of the questions, albeit at a huge price. Some of the renowned alloy wheel makers include BBS, Volk, Enkei, HRE, Konig, O.Z, Rota, Rotiform, Borbet, etc.

Below are some boring technical details for the nerd inside you:

PCD (Pitch Circle Diameter): This is the diameter of an imaginary circle drawn through the centre of the bolt holes. The PCD of the wheel should match the PCD that your car came with as standard. PCD is measured in mm. e.g: 4x100 means the wheel has 4 bolt holes and the diameter of the imaginary circle through the bolt holes is 100mm.

Wheel Offset:  The offset of a wheel determines how far a wheel will set relative to the wheel arch. Every car has its optimum offset; if the offset is too low then the wheel could stick out from the side of the car and if too high, the wheel may catch on the suspension or bodywork as it will be too far under the car. The offset is commonly shown as the letters ET followed by a number, eg: ET49. The offset is always measured in mm and can normally be found stamped on the back of the wheel.

Wheel spacers can be used to compensate for offset differences. Wheel spacers fit between your car's wheel and the hub that the wheel mounts to on the car. Wheels which sit too far inside the arches can be spaced-out using spacers. They can also be used to increase clearance, appearance and handling.

 

Wheel Width & Diameter

The alloy wheel size is generally represented as: Wheel diameter x Wheel width - example: 16 x 6.5J. The diameter is the overall diameter of the tire; width is the section between the tire mounting flanges on the wheel.

WHY ALLOY WHEELS? – Pros:

  • A set of alloy wheels and low-profile tires will make your car look better and stand out from the ordinary.

  • Alloy wheels are lighter than steel wheels; thereby reducing the total unsprung mass (The weight of wheels, tires, brakes, and rotors is called “unsprung weight) which in turn leads to better dynamics and minor efficiency gains.

  • Alloy wheels are excellent conductors of heat which conduct heat from the brakes and tires.

  • Alloy wheels improve the handling and steering response of a vehicle.

  • A good set of alloy wheels with proper offset will increase the track and contact area of the tire with the road surface.

  • Alloy wheels are less likely to corrode or rust as they are usually made from aluminum alloys.

  • You will also benefit from extended tire life with alloy wheels being lighter and cooler.

  • Alloy wheels are best paired with tubeless tires as they are airtight.

  • Alloy wheels also aid braking as the brakes tend to run cooler with alloy wheels.

WHY STEEL WHEELS? – CONS:

  • Alloy wheels are expensive than steel wheels. Forged wheels can be even heavier on your pocket.

  • Steel wheels can be easily repaired than alloys, as steel can often be hammered back into place when bent.

  • Alloy wheels tend to break or crack under impact rendering them useless

  • Steel wheels are a good option for winter days, as more unsprung equals to better traction in winter.

The big picture is very clear when you weigh in all the pros associated with alloy wheels as against to its minor cons. It eventually ends in with what the buyer is looking for in a car of his choice and aesthetics might not be one’s priority. You can never go wrong with steel wheels as they can take quite a lot of beating and abuse; that said, alloy wheels are what you’re looking for if you want the best of the bunch.

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