A Guide to Buying Alloy Wheels

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What is an Alloy Wheel?

Chances are if you are reading this guide then you already know what an alloy wheel is – but just in case you are reading this because one of your kids or your partner has asked for them as a birthday or Christmas gift then lets find out what an alloy wheel is.
Wheels used to be round with a bit of black around them and nobody took any notice of them - the wheels fitted by most car manufacturers to their cars were steel wheels. Steel wheels are more resilient to damage, and are considerably cheaper to fit and can be tidied up by fitting a nice set of wheel trims – fantastic if you are somebody that likes parking that close to the kerb that you are going to scrape the wheel trims because they are cheap to replace.
Steel Wheels though are almost always heavier, don’t really smarten up the car that much and are smaller in both diameter and width than alloy wheels.

The term alloy wheels is usually given to wheels made from a mixture of aluminium which is light weight and has the ability to be easily moulded into different styles for the fashion orientated masses.

So what are the benefits of fitting Alloy Wheels to my car?

In general, alloy wheels are lighter, more attractive, and better at dissipating brake heat than steel wheels.
You can usually fit bigger wheels to your car which means you can fit bigger tyres thus giving you more grip on the road.
By far the biggest advantage though it the fact that you can individualise you car at a relatively low cost or smarten up a tired looking car.

Terms you are going to come across when buying Alloy Wheels.


PCD stands for 'pitch circle diameter' and is the diameter of a circle drawn through the centre of your wheel's bolt holes. PCD. is measured in millimetres and also indicates the number of studs or bolts the wheel will have Vauxhall 4 stud Alloy Wheels 4x100 i.e. 4 bolt holes drilled through the centre of an imaginary 100mm circle.

Whoever came up with the way to measure an offset did not do it the most simple way in our opinion but as it is now industry standard who are we to try and change it. Simply the lower the offset number, i.e 15, the bigger the lump of alloy being the centre of the wheel hub. This means that the wheel will stick out further from the cars brake drum or disc.
The technical explanation is that the offset is the distance between the hub mounting face at the back of the wheel and the wheel's centreline.

Offset is usually stamped or engraved into the wheel and is measured in millimetres of 'ET' ET is the short form of the German word 'Einpresstiefe' which literally translates as 'insertion depth'
Positive Offset wheels have their mounting face toward the front face of the wheel. Most front wheel drive vehicles have positive offset wheels.

Zero Offset wheels have their mounting face even with the centreline of the wheel and are by definition "ET 0".
Negative Offset wheels have their mounting face toward the rear of the wheel - rear wheel drive and 4x4 vehicles will usually have a negative offset.

Why do some wheels look like they have thinner tyres on them?

Plus-Sizing or Up-Stepping are two terms given to the practice of increasing the diameter of your wheels whilst simultaneously reducing the profile of your tyres to keep the overall rolling radius the same. This means that the effect to you speedometer will be kept to a minimum. Industry standards mean that you Speedo can be effected by up to 3% when fitting aftermarket wheels - but you will usually find that reputable companies have allowed for this and put the correct tyre size on to ensure that you Speedo is kept as correct as it can be.

Fitting Alloy Wheels...

Before you do anything, check to see that you the right sort of bolts - Bolts and studs have various diameters, threads and seating, your wheel supplier should be able to advise on this. Also check to see that you the 4 plastic spigot rings which help the interface between the wheel and the hub.

Next you need to jack your car up - do this securely and be sure to use axle stands, chock wheels still in contact with the ground and apply the parking brake. Offer a wheel up to the car and check that the bolt holes line up, that the wheel locates on the hub correctly and that there is wheel arch, suspension strut and brake calliper clearance if you have up-rated brakes be SURE to seek advice and measure everything thoroughly BEFORE you order as usually if you order a set of wheels they cannot be sent back!.
The wheel bolts or nuts must be tightened to the manufacturer’s specified torque. [Be sure to re-torque them after a 100 miles or so as they will compress slightly] tighten them progressively 'till they're 3/4 tight then lower the car and complete the process. Usually the torque setting is around the 110Nm mark.
Before putting the wheel back on the ground ensure that is rotates freely and that the bolts are not too long so catching on a hub or brake drum. 

Keep them clean.

Unlike Steel wheels your alloy wheels will show up dirt a lot more. I am sure that if you have gone to your local car accessories shop then you will have seen that there's a huge variety of specialist wheel cleaners on the market, all designed to help make the job of cleaning your new rims that little bit easier, unfortunately the real key to a great finish is hard work.
Before you fit your wheels, give them several coats of good quality car polish back and front. This will help prevent the road salt, brake dust and dirt 'keying' to the surface on first use. Be sure to treat the surface of your alloys as well, if not better, than you would your paintwork. Remember, you've spent your hard earned cash on your alloys (or you've had them as a present but the same principle here!) and they're going to be subject to the harshest conditions of just about any part of the car!
Frequent washing with mildly soapy warm water [having hosed all the loose abrasive grit off first] is the best way to keep wheels clean. Never use abrasive cleansers, electric buffers or wire wool pads on your wheels.

Hope this all helps you


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