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How to buy tires and rims

Do you have a good grip on how to buy tires and rims for your vehicle?

Before we put our hard earned money on a set of tires and rims, it would be a good idea to try and understand the nuts and bolts of choosing the right set for our requirement.

It is mind boggling to note the sheer variety of  rim designs and specification that are available at a tire and rim dealership. Choosing the right set is key to a lasting, trouble free and fulfilling driving experience throughout the lifespan of the set of tires and rims. While going to a knowledgeable and helpful tire dealership is important, equipping ourselves with the knowledge is important to prevent getting into costly mistakes of choosing tires and rims that do not meet specifications..

Introduction to rims

Pressed steel rims

Pressed steel rims

For our understanding, in general, there are 3 types of rim construction fitted to vehicles.

  1. Pressed steel rims- in the early years, steel rims were fitted to most vehicles as standard equipment as in the illustration. For all intents and purposes, these rims were functional, durable and relatively cheap to produce in mass volume. This design and construction was very widely used and accepted on any vehicle with wheels. Steel is heavy and so are these rims manufactured out of a mixture of iron and carbon. It is subject to corrosion in the long run. Not so good looking but functional.

    Alloy wheel rims

    Alloy wheel rims

  2. Single piece alloy rims-in present day vehicles, most manufacturers use styled alloy wheel rims as standard equipment. This type of wheel is made out of a mixture of metal and other non-ferrous alloy. Appearance wise, they are smart and appealing to vehicle owners. It has great strength. It is lighter for the same strength as a similar sized steel wheel rim. Like all metal, it is subject to galvanic corrosion in the long run due to wear  and tear.

    3-piece wheel rim

    3-piece wheel rim

  3. Multi-piece alloy rim- it is made up of component parts as shown in the illustration. In this case it is a 3 piece rim assembled together with special grade light weight titanium bolts. Such kind of rims are forged out of light alloy and usually fitted as standard fittings on supercars which demand minimum unsprung weight and rotational inertia in order to maximize handling and performance. Big names in such kind of rim manufacture are BBS, HRE and Speedline.

Rim specifications

After extensive research and testing, vehicle and rim manufacturers have come up with suitable rims for a given model of vehicle. Most or almost all present day vehicles come with good, smart looking alloy wheel rims with standard rim specifications best suited for the vehicle.

Contemplating changing your tires and rims for whatever reasons?

Before we do any of that, let us try and understand what are the standard critical technical specifications set by the vehicle manufacturer for our vehicle. The following is a cross section view of a wheel rim showing us the critical dimensions that we need to adhere when changing tires and rims for the best handling and performance of our vehicle.

Rim dimensions illustration

Rim dimension illustration

  1. Wheel diameter
  2. Rim width
  3. Pitch center diameter(PCD)
  4. Offset
  5. Hub hole diameter
  6. Bolt pattern- 4,5,6 or 8 lug pattern

A competent tire dealer would be able to advise us the standard critical wheel dimensions of the wheels fitted to the vehicle. Knowing these key specifications will help us to make a  smart choice of suitable tires and rims for our vehicle.

Plus sizing

This is an option that can be exercised, which many vehicle owners do, to enhance the handling of a vehicle. The principle behind plus sizing can be understood from a previous post explaining about low profile tires pros and cons. It is important for us to know and follow the plus sizing guidelines failing which poor performance and handling can be expected.

Critical wheel dimensions

When embarking on an expensive tire and rim change for your vehicle, in addition to following the principles of plus sizing, it is advisable for us to adhere to the following 3 critical wheel dimensions shown in the illustration above:

  1. Pitch center diameter(PCD)- for safety reasons, the wheel must sit precisely on the hub that it is being mounted on so that the mounting nuts can be tightened securely.
  2. Hub hole diameter- the hub center hole of the wheel must be able to fit snugly into position on the mounting hub flange of the vehicle. A poor hub hole fitting can result in rim damage during impact on rough roads. This is a serious safety issue too.
  3. Offset-it is a measurement in millimeters between the mounting surface and the center line of the wheel. On the steered front wheels of the vehicle, offset determines scrub radius also known as contact patch area. As this measurement directly affects steering feel during cornering, straight line stability and the steering centralizing effect after taking a turn, getting the offset of your chosen wheel correct, is key. Deviating more than 3 millimeters from the original specification will alter the steering feel.

Tires and rims are not just for good looks only. They have a technical function to play. Plug and play with tires and rims is a costly and unsafe game and can lead to bad motoring experience.

Having a basic knowledge on how to buy tires and rims can surely help us to make a wise decision, save us a lot of technical trouble and dollars and cents in the long run.

Please leave a comment or a question that is of concern to you. I will be happy to give you a prompt reply.

Nair

2 Comments

  1. Hi Nair. This is truly an amazing post. I thought I’ve known whatever there are to know about rims and tires, but how wrong can I be.

    Never thought that black rim is made from different material.. Now I know why they are heavier than standard rims.

    On another note, it seems that the key to safety and good handling come from suitable rim/tire combination. Does each car (assuming a normal sedan car) have a typical rim/tire specs or it will differ by its maker?

    • Hello Isaac,

      I am glad that the information that you have gathered from this post has given you a good understanding about rim/tire combination. The key to good handling and safety is at stake if this combination is not properly adhered.

      Rim/tire specs differ for each and every model even if it is from the same maker. That is why it is important to check the specs, have that information in hand, before we even think about a change of tires or rims for our car.

      Vehicle manufacturers go through a lot of research and development before they decide on a certain specs of rim/tire combination designed for standard performance and handling. Any enhancement for better performance and handling should not deviate far from the reference specs. designed for that make and model of vehicle.

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