Car Wheels and Tires

For this next edition of car parts and how they work we’ll delve into the 4 points of contact that a car has with the road itself. Yes you’re right, wheels and tires! These components of a vehicle seem simple yet can be so intrinsically complicated. The rapid development in car wheels and tires meant for the road during the 20th century shaped the wheels we now have today which consist of a variety of different components such as the tire, rim and hub.

The tire tends to be manufactured separately to the rim and hub by pneumatic firms (Michelin or Pirelli to mention a few) whereas the rim and hub are usually produced by the manufacturers themselves for design purposes. Tires often compose of synthetic and natural rubber, metal wires and fabric whereas rims and hubs are made from a variety of materials depending on the manufacturer and their intentions: usually alluminum-alloy, steel or carbon.

I will also touch upon a bit of the science behind why hypercars can’t quite reach the 300mph speed threshold which many manufacturers are trying to beat (… the reason lies within the dust caps, so stay tuned in!)

Wheels aren’t just rotating pieces of metal…


BMW M4 GTSWheels can be relatively complex especially when it comes to the high performance division

There are a variety of components that go into constructing a wheel which all have different purposes however the main ones are the tire, rim and hub. There’s a lot more to a wheel and tire than just rotating to move the car. Wheels also serve to improve handling, control, braking distance, acceleration and so much more (as do many other components of a car that you wouldn’t think made much of a difference). How come you ask? Well I’ll reveal that in the following heading!

There’s so much science and engineering behind these hunks of metal which is why some wheels can be quite expensive depending on what you go for! You’ve got the tires which serve as great gripping and shock absorbing components due to how they are designed (i.e. flexible, maluable at heat etc..). The rims act as the foundation and structure of the vehicle and serve as variable components which affect control, handling, braking and acceleration and finally hubs which not only let the wheel spin freely but also is the component which connects to the axle which is what makes your wheels move.

There are also smaller components that come into play such as wheel weights to balance the tire and increase handling and consistent/stable steering and can be quite influential little things which can be the difference between a car going straight or crashing into a ditch.

Size and weight matter!


Koenigsegg Carbon WheelsCar wheels come in different shapes and sizes which all have their own purpose

Size and weight truly do matter in this context as they are yet another component of a vehicle and as we know: the lower the mass, the faster it will be! Although wheels and tires count towards a vehicle’s “unsprung mass”, it does still contribute to the overall handling of the vehicle as a whole. The physics behind it is simple and is very similar to what I discussed in my previous car parts edition: Car Suspension Parts. Newton’s 3rd Law of Motion otherwise known as inertia. The law basically states that the lower an object’s mass is, the easier it will be to make it move. In our context, the lower the mass of the wheel, the easier it will be for it to roll or move forward.

The same kind of idea applies to how large (i.e. diameter) a wheel is. The physics concept behind that is rotational inertia where a larger wheel has a larger rotational inertia leading to the same effect as described with the mass of a wheel (it will be harder to move). As such, sportscar manufactures focusing on performance strive to create the lightest wheel so to save a lot of weight. Sure it might be 5 or 10 kg however in the car industry that could be the difference between first and second place! Yes, seriously!

Koenigsegg and the “reinvention of the wheel”


We all know of that Swedish hypercar manufacturer… the one that some people can’t quite spell, yup it’s Koenigsegg. Koenigsegg is just one of the hypercar manufacturers that have a slight twist and in fact almost “reinvented the wheel”. Koenigsegg’s wheels are essentially hollow carbon structures produced through a trademarked process called AirCore Technology. Through this method, Koenigsegg saves about 20kg of unsprung weight which drastically improves handling and safety. To read more on how they are revolutionizing the hypercar industry and the exciting features, be sure to check out their blog!

You can also find out more about how they make their specially made Carbon Fiber Wheels below:

The 300mph speed record: why it’s currently improbable


Bugatti ChironBugatti used to hold the record of the highest top speed for a production vehicle of 267.86mph 

Now probably for the most exciting moment: The race for the 300mph record. Various hypercar manufacturers have been trying to achieve the golden 300mph, the current contenders are Bugatti, Koenigsegg, Hennessy, Tesla and McLaren! A Tesla I hear you say, as you question why it’s on the list of contenders. Well as you might have read in my article on Tesla and their current situation – which you can read again here, the Tesla Roadster has been hinted of a 250+mph top speed.

That’s besides the point however… the reason why the 300mph speed record is currently improbable is because there is no road legal tire to support the magnitude of forces on the wheel at that kind of speed. At that speed (depending on the size of the wheel), the tire can experience around 3000Gs of force at 250mph (that’s not a typo). As such, the tire almost starts to tear itself apart at such speeds. A dust cap on the Chiron usually weighs in at 2.5grams however at the electronically limited top speed of the Chiron it would weigh over 7.5Kgs!!

The only tire capable of the speed records set by Koenigsegg Agera RS (at the time of writing this article: 284.55mph) is the Michelin Pilot Sport Cup 2s. These are the stickiest tires which provide the most grip and actually come as a standard with the Koenigsegg Agera RS. Koenigsegg achieved this in conjunction with their hollow carbon rims mentioned earlier. You can watch the incredible record being set in the video below:

Conclusion


As basic of a function as they may have, wheels are in fact highly engineered components on a vehicle which can really make a huge difference on a vehicle’s stability, handling, braking or acceleration. Car manufacturers have to keep in mind the weight, size, materials and overall purpose of the tire in order to create the perfect one for their situation. When it comes to the hyper division, extra precautions are made to ensure maximum performance and stability. The race for the 300mph speed record is an epitome of such where 5 car manufacturers are going head-to-head in making the slightest of alterations to create the best wheel and tire to beat the record. Obviously there are other more fundamental components which determine this however the wheel and tire are the way that power is transmitted onto the road.

I hope you enjoyed this article. If you have any questions or something you might want to add then please feel free to comment them below!

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