Wheel Guide

[nisskid]

Here's a article i've put together, some of the information i have borrowed from other sites out of slackness, but most was written by me, please let me know if any of this info is incorrect as I'm sure I've slipped up here and there or even some of the info i have used is false.

One of the main reasons i've put this up is as a reference for people that ask about this stuff, some may think a lot of it is simple, but there are a lot of people who just aren't sure.

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Wheels are one of the most common upgrades for a car, the main reason is aesthetic improvements, but performance can be greatly improved simply by the wheel you select. There are three main factors in performance that can be helped with wheel selection, unsprung weight, track changes and tyre performance. A light weight wheel can greatly improve the functionality of the suspension improving performance and ride comfort. Also difference sizes of wheels allow different tyres to be used which can improve the performance of the tyre. Changing the track, or the distance between the wheels from side to side, can help balance the car and improve handling.

When it comes to looks, a lot of it comes down to personal preference, and most people can tell whether they like the look just by looking at it, so more importantly we should simply look at the more unknown parts that you can't necessarily tell just by looking at, but are very important in how the wheel will work, how it will change the feel of your car, how it will fit and whether it is suitable to fit your car at all.

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Wheel Size

Wheel size is probably the most important part of choosing the right wheel, the overall dimensions of the wheel consists of 2 main measurements, the diameter and the width; both will affect clearance under the guards, as well as tyre choice and general performance and ride comfort. Wider wheels allow you to run wider tyres, so selecting the right width is important and should be considered when deciding what tyre to use. Also having a larger diameter means to keep a similar overall diameter (with the tyre and wheel) means running a lower profile tyre, this has its advantages and disadvantages such as response in steering, harsher ride comfort, which once again means this must be taken into consideration when making the decision.

Staggered sizes can also be used, depending on the desired outcome, whether it be performance or looks, staggered size is surprisingly popular, especially width. For RWD cars it is very common to see a lot wider wheels at the rear to allow much wider tyres so that they can put the power down through the rear. Also staggered diameter is sometimes used, often seen in drag racing as well as used for presentation purpose.

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The Offset

The offset of a wheel is the measurement from the centre of the wheel (half the total width of the rim) to the mounting surface. A neutral or 0 offset, means the mounting surface is right in the middle of the rim, a positive offset means the mounting surface is positioned forward (towards the outside of the wheel) of the centre. This in effect brings the wheel and tyre in from the guard near the inside more; it will mean more clearance from your guard, but less from suspension components. A negative offset means the opposite; the mounting surface of the wheel is behind the centre of the rim. This will cause the tyre and wheel to stick out away from the vehicle closer to the guard but less inner clearance for the suspension components. When offset is displayed, it’s usually described like +32 meaning positive 32mm offset from the centre, or -21, meaning negative 21mm offset from the centre.

Not only does this mean the wheel and tyre will sit differently in the guard, it will sit differently on the ground, so changing the offset will change the track (distance between the middle of the tyres each side) your car will have. Changing the track in a car can change the handling of a car quite a lot, not only increasing track all round, but having staggered offset at the front and rear, this can change the balance of a car massively. This means research towards track and how it will affect your car is important in deciding what offset you decide to run.

To compare the effects of changing the offset and width of your wheels use the Offset Calculator

http://www.1010tires.com/WheelOffsetCalculator.asp

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Stud/Bolt Patterns

Different cars have different stud patterns, this means wheels are made to fit different cars, having a less common stud pattern will limit your choice of wheels as not as many will be made to suit, but often wheels even have multi-stud patterns which accommodate for different stud patterns on the same wheel. It is important to know what bolt pattern your car is so you know what wheels are available.

Most Bolt Patterns are represented in the following manner:

5/114.3

The "5" indicates the number of holes in the wheel for the bolts to enter and mount the wheel onto the car.

The "114.3" indicates the PCD (Pitch Circle Diameter), the diameter of the bolt circle measured in millimetres or inches. 4 & 6 bolt wheels are measured from the centre of one bolt hole to the centre of the bolt hole directly across from it. On a 5 bolt pattern, it is a bit trickier to measure without special tools. Imagine a circle running through the centres of each bolt hole. You would measure from the centre of one bolt hole to the imaginary circle that lies between the opposite two bolt holes.

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Wheel Construction and Quality

Surprisingly for such a critical part of the car's safety, the regulations and standards for wheels are pretty slack over the world. Some countries simply have none, some have vague standards that aren't really enforced, and some countries like Japan and Germany have some decent standards and tests the wheels have to face.

This means the quality is very wide spread with wheels. The quality of a wheel is a direct result of the manufacturing process used.

One-Piece Wheels

This is the most popular type of wheel where the whole wheel construction is one piece including the disk and the rim. This type of wheel can be made using a variety of different techniques (see below).

Multi-Piece Wheels

This type of wheel uses 2-3 major components secured together to create a full wheel. This means that the different components can utilize different processes of manufacturing. Using a forged disk or face means maximum strength, and using a spun rim means similar strength but it keeps the overall production cost down.

The 2-piece wheel is more common than the 3-piece wheel; it does not have the same range of applications as the 3-piece but it is usually a lot cheaper to buy on the market. The different parts are often held together by bolts connecting the face/disk onto the rim, or sometimes they are simply pressed together and welded.

Gravity Casting

Gravity casting is the most basic technique of casting by using gravity fill the mold. Gravity casting keeps production cost down and is usually a popular method for wheels that are visually oriented and when producing a lightweight wheel is not very important. Since the process uses low pressure to fill the mold, the alloy isn’t very densely packed in the mold leading to low strength, this means more metal is needed meaning more weight to achieve a safe amount of strength within the wheel.

Positive Pressure Casting

Positive pressure casting uses pressure to compress the molten alloy into the mold more forcefully compact the alloy in the mold more. This increase in density improves the strength over the gravity casting technique leading to better results. The only downside to pressure casting over gravity casting is it has a higher production cost. Low pressure is the most popular process used for alloy wheels especially in the OE market as it provides good strength whilst still keeping down production costs. Some manufacturers produce wheels that use higher pressure when casting with special equipment, this is of course the most expensive pressure casting technique but it provides great lightweight properties.

Spun, Flow Forming or Rim Rolling technology

This specialized technique starts with a pressure type of casting and then spins the casting, the outer portion of the casting is then heated and then steel rollers are pressed against the rim area to pull the rim to a final width and shape. The process used a combination of heat, pressure and the spinning motion to create a rim with the strength properties similar to a forged wheel without the higher production cost of forging. This is sometimes used for the OE market in high performance cars, and is also popular for aftermarket wheels. Spun rims are often used with forged faces or disks as it saves a lot of production costs but still achieves similar results.

Forged or Semi-solid Forged

Forging is the ultimate in wheel production, it is the process of forcing or pressing a solid billet of alloy into the forging dies under massive amounts of pressure. This obviously creates a very dense wheel, which produces maximum strength which means less metal can be used which means less weight. Of course as you would expect the production costs is massive, so it’s not a favoured process unless lightweight is high on the agenda.

Semi-solid forging is a similar process but instead heats the billet of special alloy to an almost molten state and then the alloy is forced into the mold at a very high rate. The final product offers mechanical properties very similar to a forged wheel but has a lower production cost. SSR (Speed Star Racing) currently owns the license to this process and are the only ones to use it.

Chrome

This is a popular finish on wheels which results in the surface to be bright and reflective like a mirror. The process involves the wheel being stripped to its bare metal and several different layers of metals being applied which is finished off with a nickel layer that creates the shiny finish. Chrome wheels are usually heavier and can be weaker due to the extra metal and sometimes the use of acid in the stripping process.

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Lightweight Wheels and Unsprung Weight

There is a lot of emphasis on getting a lightweight wheel, especially within the performance tuning world, but it seems a lot of people aren't really aware of what a lightweight wheel does. Firstly what makes a lightweight wheel? Well basically it’s a wheel that doesn't weigh much in comparison to other wheels its own size, often what I do when I'm deciding on what wheel to buy I decide the size I'm after then use a site WheelWeights.com to compare the wheels and weights to other wheels of the same size, you get an idea of what is the general weight for wheels that size then anything well below them is a lightweight wheel. The way to make these wheels light is pretty basic, using as little amount of metal as possible, the issue is you do not want to sacrifice strength too much, so what good manufacturing companies do is use different methods of creating the wheel, different techniques allow them to create extra strength out of the same amount of metal and weight, this means they can use less metal to achieve the same amount of strength, leading to less weight. The only issue is, these processes cost a lot more money so the wheels cost a lot more. Now just because a wheel is light doesn't mean its a good wheel or it has used a superior manufacturing technique, a good wheel keeps good strength and rigidity properties as well as keeping weight down.

Now back to what a lightweight wheel does and what its benefits are. Sure when it comes to making a car go fast you strip out things you don't need in the cabin to make the overall car lighter improving performance, but how does a kg here and there off each wheel justify the extra money they cost when u could just take out a radio or simply skip lunch and make up a similar amount of weight? Well this is where we have to clarify the 2 types of weight in a car; there is unsprung weight which basically includes all of the suspension and parts that move with the suspension including the wheel and tyre, and the sprung weight which included everything else. Now a lot of people believe in a general rule that directly relates sprung and unsprung weight, such as "every 1kg of unsprung weight is equivalent to 15kg of sprung weight, meaning 1kg off all 4 wheels = 4 x 1kg = 4kg, so 4kg x 15 = 60kg's, meaning take off 4kg off unsprung weight (1kg from each 4 wheels) and its equivalent to saving 60kg's of sprung weight.

Let me just say that anything like that is completely false as although sprung and unsprung weight have the same properties, they affect different components, so really it’s like saying every 1hp you add to your engine, your brakes will work 10% better, it’s just not correct.

Now if you’re really interested in unsprung weight I recommend reading up on it as I don't want to get to far into it, but basically the suspension has to move up and down to absorb bumps and keep the tyres fixed to the road and save the force of the bumps being transferred into the chassis, with this movement having more weight will make this movement harder having to move the extra weight, reducing the weight allows the suspension components to move easier and quicker, making the suspension more responsive and meaning the suspension can absorb the bumps better, leading to improved ride comfort and improved traction and handling.

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The Components of a Wheel

The components of a wheel all play a critical part in the function of the wheel, they sometimes take on different names depending on where you’re from, but there are some common names for most components of the wheel.

The Hub and Centre Bore

The hub of a car is a small ring that protrudes out of the mounting surface for the centre bore of the wheel to fit onto. The measurement of the hub can also be referred to as the pilot bore.

The centre bore is the hole in the centre of the wheel that centres the wheel on the hub of the car. Since most wheels are mass produced, they have a large centre bore to accommodate several different vehicles. This is why usually a hub centric ring is needed to fill the gap and make it a firm fit to make sure the centre bore cannot move around on the hub which can cause vibrations. The hub centric ring is just a small metal or plastic ring and can be purchased from most wheel and tyre stores.

The Disk

The disk of a wheel is also known as the face of a wheel as it is most visible looking at a wheel fitted on the car. The disk includes the spokes, mounting surface, and lug holes.

There are different types of disks, referred to as high and low disk, or sometimes referred to as A, B and C, or O, A and R depending on the manufacturer. A high disk, will tend to have more space behind the spokes where it mounts to the mounting surface, this also means that the disk will stick further out away from the car relative to the barrel or the rim. A low disk will mean the opposite; it will have less space behind the spokes, and will stick in further relative to the rim. A high disk type is usually used on cars with big brakes that need to be cleared by the spokes, and low disk's are usually used on smaller brake cars and is often preferred for styling reasons as a low disk often means more dish or concave spokes.

This is why you often see cars with rear wheels having a lot of lip or dish, and the front have less; this is because as the front brakes are usually larger than the rear, the front usually needs more clearance meaning it needs a higher disk wheel, whereas the rear can use a lower disk.

The Rim/Barrel

The rim is the barrel of the wheel which basically connects the tyre to the disk. Its main job is to hold the tyre in place and keep pressure sealed under the tyre to keep it inflated. The design of this can actually be surprisingly important, especially the bead seat. The Bead Seat is the area of a rim where the tyre walls sit and seal to prevent air leakage. A rim can have a slotted or knurled bead to reduce slippage in high performance applications. Different designs can be easier and harder to bead a tyre which can be important when a smaller tyre is stretched over a wider wheel making it hard to bead.

[adam-__-]

Thanks for putting that all together mate. Learnt a few things I would've never looked up to read. Before I read it, I was expecting things similar to those on the carbible website. Reading things you don't even need/want to know. hahah.

I hope people actually read this and not just skip it because it's too long. They'll learn a thing or two..

[nisskid]

cheers mate, yeh definately worth a read, when u consider how many wheels there are out there, its really good to know what to look for. took me a while to write, and im still editing things here and there as i notice mistakes and learn new things. This is just a starting basis, it covers most general stuff, but i would love to gather further info from people to add to it.

[Basti]

thanks nisskid. looks good and informative. i'll read when i have the time

[nisskid]

no probs

[n15m0]

Good stuff...should request the mods to sticky it...!

[NA_Goodness]

Thats wot I was going to do. Thats fantastic mate!! I havent read it yet, but i will eventually!

[nisskid]

yeh might do that, looks like N1GTR is the forum mod, but he hasnt been on in a while.

[siddr20]

+1 for sticky!!

Great write up and very detailed!!

Hopefully this read will clear a lot of doubts for everyone!!

[adam-__-]

I honestly think those who really need to know the information will be too lazy to read it. They'll open up the thread, see how long the post is and get scared away.

[nisskid]

I honestly think those who really need to know the information will be too lazy to read it. They'll open up the thread, see how long the post is and get scared away.

yeh thats my worry as well, owell, i think if someone really wants to find out more they will spend the time to read it.

[joeyjoejoejuniorshabadoo]

great read!

[M'ck'y]

Thanks for putting the wheel information together, now we gotta shop for wheels

[R34~neo6~turbo]

awesome info tnx mate, ill keep this in mind when i shop for my wheels

[RustyR32Gtst]

This may also be helpful -

http://www.miata.net/garage/tirecalc.html

[nisskid]

This may also be helpful -

http://www.miata.net/garage/tirecalc.html

the thread was designed for just wheel info, but as far as tyre sizing goes this is much better: http://www.1010tires.com/TireSizeCalculator.asp

[bayslideblue]

I honestly think those who really need to know the information will be too lazy to read it. They'll open up the thread, see how long the post is and get scared away.

I wasn't scared. It was good reading. I never new what "offset" was until now.

Cheers,

[Milkshakex]

really informative and it didn't scare me away

I fought with it =P

[GTR-N1]

Many Thanks Stewy

This is a great refernce to come back to...

Tez

[Luciano]

well done mate, this was a good lunchtime read. Im actually in the market for rims at the moment, so this info was very good knowledge to gain