Guide for fitting larger wheels

Workshop - DIY Guides

One of the most common questions asked by MightyBoy owners is "will X wheels fit?" This guide aims to help you choose what wheel and tyre combination will be suit your needs.

With all mechanical work on your vehicle please make safety your first priority and remember, this article is to be used ONLY as a guide to assist the reader and should not be considered a replacement for mechanical expertise. If you are unsure about any aspect of this, or any other guide provided on the Team MightyBoy website, then please seek the advice of a professional in the area concerned. Team MightyBoy contributors take no responsibility for the accuracy of technical information provided, nor is the author of this document responsible for any harm or injury incurred as a result of following any instructions written in or implied by this document. When making modifications to your vehicle, always abide by any rules or regulations set forth by your state Government’s vehicle standards department or road and traffic authority.

Before choosing your wheels

There are a number of considerations to be made when choosing the right set of wheels for your MightyBoy, but they boil down to a single choice - performance or looks. If you want the best handling then you should be looking at something around 13" in diameter. Looks on the other hand are completely subjective, so you can go as large as will physically fit within the wheel arches (or larger if you don't mind slicing up the bodywork!).

The specifications for standard MightyBoy wheels are:
Diameter: 12"
Width: 4"
PCD: 4x114.3mm (diagonal distance between wheel studs)
Tyres: 145/70/R12 (at some point most MightyBoys were fitted with larger commercial-grade tyres)

Rolling diameter

You can probably tell by the standard specs that Suzuki chose wheels based on low cost rather than quality, and this is reflected in the handling performance. There is another reason for such small wheels, and that's because the standard MightyBoy motor has very little power, and smaller wheels put less load on the engine and have less rolling resistance - meaning more power gets to the ground. Fitting wheels that are a little bit larger isn't going to dramatically affect engine performance, but as you increase wheel size it is important to choose a size that suits your application. You can also maintain the standard rolling diameter (or close to it) by choosing a lower profile tyre when installing larger wheels.

Legality

Under the proposed NCOP for light vehicle modifications the rule is that wheels can be 15mm larger in overall diameter (wheel and tyre) from standard. However as the MightyBoy is classified as a commercial vehicle, the increase can be up to 50mm. Width increase is limited to 26mm (1"). Wheels any wider or larger than this will require certification by an engineer.

As a side note, insurers will only legally cover wheels that are within the above guidelines.

Wheel weight

A very important consideration when choosing wheels for your MightyBoy is that the standard wheel and tyre weighs around 5kg. This is lightweight, and it is worthwhile trying to get wheels as close to this figure as possible. Heavier wheels put more stress on steering, suspension and wheel bearings.

Wheel arch clearance

A MightyBoy doesn’t have the most generously sized wheel arches, and you need to take this into account when looking at replacement wheels and tyres. Depending on your choice of wheels you may need to have the arches rolled to provide enough clearance to prevent the tyres from scrubbing. If your MightyBoy is lowered then rolling the arches is very necessary, and the rear upper bump stops will require trimming to prevent the insides of the tyres from scrubbing. After fitting new wheels be sure to check all clearances carefully before driving.

So what wheels will fit?

It is difficult to say what wheels will fit without requiring modification as there are many factors that need to be taken into account, including wheel offset, width, overall diameter ride height and suspension condition. The following table is an indicative guide.

Notes:
Required wheel offset is between +38mm and +42mm depending on wheel width. (Higher offset required for wider wheels)
Wheels wider than 6" are considered too wide to fit without substantial body modifications and have been excluded.

Rim diamater x width (inches) Recommended tyre size Comments
12x4 145/70/R12 Standard wheel and tyre combination
12x4 to 12x5.5 145/70/R12 to 165/65/R12 No known issues
13x5 155/70/R13 Most likely choice to fit without scrubbing.
13x5.5 165/65/R13 or 175/50/R13 175 tyres have same rolling diameter as standard.
13x6 175/50/R13 175 tyres have same rolling diameter as standard.
14x5.5 155/60/R14 or 175/50/R14 Fit nicely but will require rolled arches.
14x6 175/50/R14
15x5.5 165/45/R15 or 165/50/R15
15x6 165/45/R15 or 165/50/R15
16x5.5 165/40/R16
Wheels and tyres difficult to source.
16x6 165/40/R16
Wheels and tyres difficult to source.
17x5.5 165/35/R17
Wheels and tyres difficult to source.
17x6 165/35/R17
Wheels and tyres difficult to source.

Wheel studs / wheel nuts

MightyBoys have a 10mm stud diameter, as opposed to most other vehicles which have 12mm studs. This can make alloy wheels difficult to fit as the standard wheel nut is too small and chews into the alloy. It is strongly recommended that you fit alloy wheels with acorn style wheel nuts. These have a large tapered collar that will centre the wheel on the hub and won't damage the wheel.

There are various companies ('Nice Wheel Accessories, for example) who produce suitable 10mm acorn wheel nuts.

Other things to consider:

The MightyBoy has a 114.3mm stud pattern, the same as some other FWD cars of the 80's and 90's. (80-86 Nissan Pulsar, 80-86 Holden Astra, 80-86 Ford Laser, 80-86 Mazda 323, 86 onwards Hyundai Excel, 84-98 Suzuki Swift, etc)

If you're considering wheels from a RWD car, note that the offset will be incorrect which can damage the wheel bearings. This is due to the extra pressure applied during cornering.

Nothing larger than the stock 12” rim/tyre will fit in the spare tyre recess without making some modifications. But if you did happen to get a flat, running the 12" on the rear of the ute won't damage a thing. It just means that if you get a flat on the front, you'd have to shuffle a few tyres around to accommodate the different wheel sizes. On a front wheel drive car, you should always put the spare wheel on the rear axle if it is a different size to the other wheels.

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