An Amateur Mechanics Guide to Buying Wheels With Tyres

No matter one's mechanical knowledge, the need to buy and replace one's tyres is inevitable. Whether this need comes from flat or simply worn out tyres on an older vehicle does not matter. However, knowing what to look for and how to do it is essential. To accomplish this, many amateur mechanics and professionals alike enjoy the time-saving option of buying wheels with tyres. This combination allows them the ability to update the look of vehicles whilst also replacing their worn out elements. However, buying wheels and buying tyres each require a separate process of evaluation and decision making that is necessary before making a purchasing decision.

Indeed, there are three distinct evaluation criteria which buyers must evaluate for each element. For wheels, this means determining stud pattern and PCD, wheel offset, and wheel dimension. For tyres, buyers must consider aspect ratio, tread, and silica. Carefully completing both of these evaluations makes the buying process for wheels with tyres much easier.

Also referred to colloquially as rims or wheel rims, technically speaking a car's wheels refer only to the metal part of the wheels and tyre units. Changing one's wheels is not often called for in terms of wear, but it does add a distinctive new and updated look to a vehicle. However, one must take care to choose the right wheels for a car which involves calculating three measurements: stud pattern and PCD, wheel offset, and wheel dimension.

Determining Wheel Stud Pattern and PCD

A wheel's stud pattern and pitch circle diameter (PCD) is the first measurement one should take when interested in buying new wheels with tyres. This measurement is expressed in a two digit, fraction-like number.

Determining Stud Pattern

The first measurement, the stud pattern, is easy to take. It begins by looking at each wheel and counting the number of studs holding them in place. There are 4, 5, or 6 studs, though occasionally 3 studs appear on smaller vehicles such as motorcycles and scooters. The stud pattern is thus a simple expression of the number of studs on each wheel.

Determining PCD

The PCD is then taken by drawing a line through the centre of every stud hole on the wheel and adding them up to get a total diameter. This measurement can be taken by using a ruler and starting on the left side of each hole and measuring across to the left side of the next hole all the way around.

Putting Stud Pattern and PCD Together

The final result of taking these two measurements is a two digit measurement written as a fraction. The first number is the number of studs (4, 5, or 6) and the next number is the diameter of those studs in millimetres. For example 5/120 signifies a 5-stud wheel with 120 millimetres diameter.

Determining Wheel Offset

A wheel's offset is a measurement of the distance in millimetres between the centre line of a wheel and its mounting face. This measurement is either positive or negative and can mean different things. A positive offset means that the mounting face of the wheel is under the car and is common in Hondas and Subarus. A negative offset means that the mounting face is found on the back of the wheel, behind the centre line. Negative offset wheels sit further out from the car and are common on 4-wheel drives.

How to Calculate Wheel Offset

Calculating a wheel's offset is a four-step process which results in either a positive or negative number which correlates with the explanation above. The process is as follows:

1. Measure the car's backspace; start at the bolt up face and go to the back edge.
2. Measure the rim's width from edge to edge.
3. Divide the second number by 2 to find the centre line of the wheel.
4. Subtract the centre line measurement (#3) from the backspace measurement (#1).

Once the offset is determined using this method, it is very important that buyers stick to this number. This is because, often, changing a vehicle's wheel offset also increases the load on axles, bearings, steering components, and suspension joints. Failure to stick with the proper offset can lead to wear on a car's suspension and, eventually, failure of its suspension.

Determining Wheel Dimensions

The final calculation that buyers need when looking for new wheels is the wheel dimension. This is determined by measuring three separate components: the width, diameter, and rear spacing of the wheel. These measurements are taken in the following manner.

Wheel Width

Measure a wheel's width from the inner bead seat to the outer bead seat. This number, to be taken in millimetres, is separate from the physical width of the wheel measured when calculating wheel offset.

Wheel Diameter

The diameter of the wheel is measured, in millimetres, from bead seat to bead seat. This is the measurement needed even though the physical size of the wheel is actually larger.

Rear Spacing

A wheel's rear spacing is the measurement, in millimetres, between the the outside edge of the back of the wheel to its mounting face. Take this measurement by placing a ruler along the back of the wheel through to the mounting face. This is the same measurement used to calculate the wheel's offset.

The second item that must be assessed when buying wheels with tyres is the tyres themselves. Though the choices are not as limited to measurements as with wheels, there are still several factors to consider before choosing tyres for a car. Minimally, this includes the tyre's aspect ratio, tread, and silica.

Tyre Aspect Ratio

Also known as a tyre 'profile' the aspect ratio is the first item that buyers must consider. A tyre's profile is a number which expresses the height of that tyre's sidewall as a percentage of its width. This number is often identified in what are known as sidewall markings of a tyre which collectively express a tyre's size. These markings are found on any tyre either in a store or already on a car.

There are three main components to a tyre's sidewall markings which are expressed in numbers in the following form: 205/55R16. In order, these markings are the tyre's width in millimetres, the aspect ratio, and the diameter of the rim, in inches, which the tyre is designed to fit. The height of the tyre can then be determined by multiplying its width (205) by the aspect ratio (55 per cent). In this example, the tyre in question has a height of 113 millimetres.

The second factor which buyers must consider when looking at tyres is the tread on those tyres. The tread of tyres is the part of the tyres which contacts the road. Each tyre has a tread made of a specific compound which subsequently impacts that tyre's performance. The goal of tyre manufacturers is to make tyres of a compound which is capable of achieving maximum grip while still maintaining both heat resistance and durability.

Most companies use a mixture of materials in the making of a rubber compound for their tyres. They vary the percentage of the materials in order to produce tyres which exhibit varying performance characteristics. A list of the most common tread types and their general characteristics is expressed in the table below.

General Description

Tyre has a small pattern with tight spacing

Designed for use on dry and wet surfaces and normal driving conditions

'V' shaped pattern with wide gaps

Designed for use in ice/snow and mud

Same 'V' shape pattern as one-direction tread, but with the ability to provide traction in both forward and reverse directions

Designed for ice/snow and mud

Same 'V' shape pattern as one-direction tread and non-directional tread with a more rounded shoulder

Designed for icy and muddy conditions on long drives

Designed to endure more wear and tear than other 'V' shaped tyres

Tyre with very deep parallel gaps which prevent the accumulation of small stones or damage from larger rocks

Designed for agricultural vehicles which spend a lot of time on rocky terrain

Choosing the proper tyre tread is generally an exercise in assessing one's own needs and intentions for vehicles. Although cross-country treads and deep rock treads are generally for more more specialised use, the other three all offer important benefits that may suit drivers in certain climates or circumstances.

Tyre Silica

The final element to assess when choosing tyres is a tyre's silica. Silica is a relatively new addition to tyre composition or tread compound which adds to performance. Silica's main advantage is its ability to reduce the car's fuel consumption while concurrently maintaining performance in important areas such as the vehicle's grip in wet conditions. Silica also has the advantage of improving a car's skid performance without the common side effect of compromising the tyre's tread wear. Popular names for tyres which use silica are fuel saver tyres, green tyres, and low-rolling resistance tyres.

Buying Wheels with Tyres on eBay

After determining the size of wheel needed and the type of tyre desired, buyers are ready to find the wheels with tyres that they need. Although wheels with tyres are widely available in automotive stores and through larger retailers, eBay offers customers specific benefits should they choose to shop there.

The eBay Difference

Because it is a marketplace rather than a single retailer, eBay offers buyers far more selection and price advantages than traditional stores or other online retailers. This is because sellers compete with each other on the eBay website for your business. In addition, eBay provides a number of protective benefits to buyers through its partnership with PayPal as well as its detailed feedback system, which allows buyers to evaluate sellers based on past performance on the site.

Searching for Wheels with Tyres on eBay

Searching for wheels with tyres on eBay is quite simple. The site is designed to allow buyers to conduct a general search from any page through the general search bar. Buyers who know their specific needs can simply type in their search terms into the field, such as "Toyota wheels with tyres", and they will be provided with several hundreds or thousands of results. From there, eBay offers search limiters which allow buyers to narrow down their results according to the calculations described in the sections above. This includes tyre width, aspect ratio, and manufacturer.

Conclusion

The choice of buying wheels with tyres is a great way for car owners to help fix a problem or update their vehicles. However, since this purchase involves two separate parts, it is necessary to take the time to evaluate both of them separately.

When shopping for wheels, this means gathering three measurements: stud pattern and PCD, wheel offset, and wheel dimension. For tyres, there are three additional factors to consider: aspect ratio, tread, and silica. Only after going through all of these evaluations are the buyers ready to move on to the purchasing process of wheels with tyres.

eBay is a great place to buy wheels with tyres since it offers its users a few unique benefits such as built-in competition, the benefits of PayPal, and the seller feedback system. Searching for wheels with tyres on eBay is easy as well, making the process of acquiring these important auto parts that much easier.

Tags:
Have something to share, create your own guide...
Explore more guides