What You Need To Know About Changing Rims

One of the most common modifications that some people don't even consider a modification is the replacement of factory alloy rims to something from the aftermarket.

Some people change their rims for aesthetic reasons, some do it because it’s packaged by tyre shops when they do their regular tyre replacements and others want some sort of performance gain.

In this simple introduction to alloy rims, we’ll give you all the key information you need to understand alloy rims and what to look out for when you’re shopping for new ones; or at least not to be cheated by shady dealers into buying something not right for you.

The first thing you need to know is that most cars these days are already fitted as standard with aluminium alloy rims, hence the term alloy rims, which is a shortened version of that, in case you were wondering what alloys they are made of.

As opposed to steel rims, which is the other de facto version on some cars that you might remember seeing on especially taxis that have an ugly, dark coloured wheel with a plastic centre piece usually painted in silver covering the wheel.

Alloy wheels are lighter in weight, which helps to save the amount of effort the engine has to use to spin them thereby saving you fuel. Additionally, aluminium alloys can be cast or forged into various different designs, allowing for many customisation options you undoubtedly would have seen at a wheel purveyor.

The down side however, is that alloy rims are softer than steel ones, which means that they are more susceptible to damage from serious impacts like hitting a large pothole at speed, which can result in the wheel being warped and out of alignment.

However, as you’ll see, alloy wheels can be made so well these days that strength can be quite comparable to steel wheels, at a fraction of the weight.

The two main methods of producing an alloy rim are casting and forging. Casting involves pouring the molten aluminium alloy into a mould while forging involves a solid block of aluminium being heated and pressed into shape via specialised machines.

There are finer details as to how the rims can be cast or forged, because each process has several variations that different manufacturers use to either improve strength or reduce weight or both, but we won’t cover those details in this guide.

Suffice to say that the key difference between the two types of rims produced (cast alloy rims and forged alloy rims) is in terms of cost, because forging produces stronger and lighter rims than casting, so you can expect to pay up to several times more than a comparable cast alloy rim.

Our general advice is that you should stick to cast rims unless you’re after serious high performance, because most of us tend not to be able to maximise the performance of a set of forged rims fitted to a regular bread-and-butter vehicle.

On a high performance vehicle like some Ferraris, forged wheels come as standard because weight saving and stress management on poorly surface racetracks matter. But on a regular car, a set of cast alloy rims will do just fine, considering how some manufacturers use certain techniques that make lightweight and strong rims using casting anyway.

Another key thing to note is the wheel size – and by this we don’t mean the more commonly understood diameter size.

Most people are familiar with the diameter of their wheels – 15 inches all the way to 20 or even 22 inches are commonly seen on cars of all ranges these days. But in addition, the full wheel size is actually something like “9Jx19 ET29”, which refers to 9 inches wide, J means for passenger cars, 19 inches and a positive offset of 29 mm.

Confused? Yep. That’s why we’re here to help.

In simple terms, ensure that you get the right width and diameter that your car’s manufacturer has specified for it. Just because you like to get as large a wheel as possible to “fill the wheel arch” doesn’t mean your car will fit any size you like.

Manufacturers have taken into consideration suspension clearance and travel as the wheel moves up and down across uneven road surfaces, so only fit sizes recommended for your car by the manufacturer.

As for offset, this refers to how far the wheel mounting hub is situated away from the centre of the wheel. This is typically a positive number, which means that in the example above the hub is 29 mm away from the centre, towards the outside of the wheel.

Negative offsets are not as commonly found, but the result of a negative offset is a deep dish wheel, that has spokes which appear to be recessed into the rim rather than towards the outside of the rim as in the case of positive offsets.

The offset of the wheel affects how close to the suspension components the wheel is when mounted, so be sure to get the right offset as recommended by the manufacturer or you risk the inside of the wheel rubbing against suspension components or compromised handling if the wheel is mounted too far away from the axle.

In real world terms, this translates to an important piece of buying advice in that not all designs you fancy come in the correct diameter, width and offset ratings. Some wheel designs may have the right diameter and width, but not the right offset for your car.

It is better to get a wheel design that meets all the right criteria, rather than to stick to a design you like but is of the wrong specifications which could ultimately compromise handling and increase wear and tear on your tyres.

Make sure you do your homework on the manufacturer specs for wheels for your car to avoid being sold a set of wheels that are not ideal for your car. Especially so if your car can be fitted with a staggered configuration, which means the front and rear wheels aren’t of the same width, usually found on performance oriented cars.

#Cars #Autos #Wheels #rims #Offset

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