Wheel and tyre upgrades

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This is a guide to help you sort out wheels and tyres for your MightyBoy.

Before you go out and spend your money on a set of new wheels, there are a number of things you need to consider. For starters, the standard wheel size on a MightyBoy is 12x4.5" with a 145/70/R12 tyre, and 4x114.3mm stud pattern.
While this combination doesn't provide a lot of grip, Suzuki fitted them for a couple of reasons: rolling diameter and unsprung weight.

A standard F5A (543cc) MightyBoy doesn't produce a lot of power or torque, so the standard rolling diameter was chosen to keep unnecessary load off the engine and gearbox. This is especially important if you use your ute to carry anything.

With any vehicle, keeping unsprung weight (components on the end of the suspension) as low as possible helps with handling, acceleration and braking. On a MightyBoy this is critical as the suspension and body are not particularly heavy duty, and extra unsprung weight has a noticeable impact on performance.

To make your decision about wheels easier, this page is broken up into sections based on how much effort is needed to upgrade. From bolt-on, to solutions that need more significant supporting modifications.

Of course there are a heap of other variables that impact what wheels will fit your ute, including the ride height, type of suspension and any modifications to the position of the wheel made by hub changes or camber adjustments. So treat the info on this page as a rough guide and use a website like tiresize.com to help calculate the appropriate wheel and tyre size for your needs.

A MightyBoy with standard wheels and tyres

Standard size wheels are 12x4.5" fitted with 145/70R12 tyres.

Rolling diameter: 508 mm

Weight: ~5kg per wheel (with tyre)

Revolutions per kilometre: 627

A note about wheel nuts

The MightyBoy has 10mm wheel studs as opposed to 12mm found on most other cars. The wheel nuts also have a very small taper area, much smaller than what is needed for most aftermarket wheels. Because the hubs don't have a centre locating collar, it is critical that you purchase wheel nuts with a larger taper area to make sure the wheels are centred on the hub and don't vibrate. The most common style are called acorn nuts, however you can get blank nuts in most common styles and have them tapped with a 10mm thread. (10x1.25 mm to be exact)

Don't get tricked by track width

Observant owners will notice that the track width (distance between the wheels on the same axle) is different on the front and rear of a MightyBoy (1215 mm and 1170 mm). If you want to square the track widths you have the option of staggered wheel fitment, meaning the rear wheels can be roughly 15mm wider, or have 15mm lower offset than the front.

I just want wheels that fit without modifications or scrubbing

If you're looking for a bolt-on swap for the standard steel rims then you should be looking at wheels sizes between 12x5" and 13x5.5" with an offset of +38 to +42 mm. Anything in this size bracket should fit with little fuss, however for 13" wheels you will need to choose an appropriately sized tyre to prevent scrubbing - 155/65/R13 is commonly used. The upside of switching to 13" wheels is that tyres in this size are fairly cheap to buy, however the increase in diameter (531 mm) causes a 4.5% calibration error with the speedo. A 155/60 or 165/55 tyre would be ideal but these sizes are very uncommon. 175/50 are available, but the additional tread width can create scrubbing issues.

I don't mind making a few modifications

Wheel options open up slightly if you're prepared to do some minor modifications - trimming metalwork and rolling the lips of the wheel arches to create clearance. A protrusion on the rear upper bump stops is a common spot for tyre scrubbing and can be filed/cut back slightly, and the wheel arch lips (particularly the front) can be rolled fairly easily, but can result in cracked paint if not done correctly.

The extra clearance allows for a range of wheels from 13x6" to 15x6" with an offset between +38 to +40 mm. The limiting factor is the physical size of the wheel arches, particularly the rear which are smaller diameter than the front. You can go up to 17x6" wheels, however this size is highly uncommon outside of Japan and almost impossible to find in the required 4x114.3 stud pattern.

For tyres the common sizes for 13" are listed in the section above. For 14" the best size is 165/50R14, although 175/50 is more common to find. 15" is 165/50R15, which is common to a lot of kei cars. All of these tyres create varying speedo calibration errors, so take that into consideration.

I have an angle grinder and I'm not afraid to use it

It doesn't take long to reach the limits of the factory bodywork, but if you're willing to get creative (or destructive) then the sky is the limit!

Fitting flares is the obvious way to fit wheels wider than 6", and most commonly used when RWD offset wheels are being fitted, usually in the 0 to +15 offset range. Cheap flexible plastic flares are available from ebay is a range of widths, or there are custom-fitted flares available from Japan through Ginyakobo but these are relative expensive with shipping to Australia.

Flares by themselves become less practical on lowered utes with wide wheels as the tyres will still foul on the factory bodywork. That's when it's time to break out the angle grinder and attack the bodywork, and by that stage this guide becomes fairly redundant. Good luck!