The tyre size that you run on your 4WD can make a pretty substantial difference to how capable it is off road, along with how well it brakes, how much power you lose. Ultimately the moment you change tyre sizes, it has a big effect on your vehicle.
People fit different tyre sizes every day of the week, and whilst there’s nothing necessarily wrong with doing so, you need to make sure that your chosen tyre size suits the wheel that you are fitting it to.
In general a good tyre shop will do this for you, and will usually refuse to install tyres that aren’t suitable for the wheels, but they do occasionally slip through. It is possible to fit tyres to a wheel or rim that is under the recommended minimum width, and you’ll have issues going forward.
Tyre size and wheel width
Every wheel that you purchase comes with a list of tyres that it can, and cannot run. For example, you’ll get away with 265/75/16’s on 7 inch rims. However, if you want to go to 265/65/17’s you need to go to an 8 inch wheel. Likewise, you won’t fit 285/75/16’s on 7 inch wide wheels; they need to be 8 inch.
It can go the other way too; if your wheels are too wide, you’ll have issues running normal tyre sizes, and this is something to be aware of.
If you want to know exactly what wheel widths suit what tyres, its all in the tyre and rim association book, which you have to pay for. It’s $90 a manual online, or $100 if you want a physical copy.
Ultimately, contact your tyre shop and discuss options with them before you commit to anything; they’ll have this and know what suits best.
When we install new tyres, we look at a myriad of other things
Is the tyre size common?
I see people purchasing the most random tyre sizes all the time now, just to get the absolute maximum size, or to get a particular tread pattern. My advise is to stick with tyres that are relatively common, for two reasons.
Firstly, they are almost always cheaper, and secondly because they are far easier to get. If you get a puncture on the Gibb River Road and need to replace a tyre, good luck getting some fancy size that only the big city tyre shops carry. If you do manage to get one, you’ll pay through the roof for it.
Does the tyre and wheel type suit our intended purpose?
There’s so many 4WD tyres and wheels on the market today. At the end of the day, the most important thing is whether its going to do what you want it to. Does the tread pattern suit where you are going to be using the vehicle? If you are going where punctures are prone, are they light truck tyres with a decent sidewall?
Are the wheels strong enough for hundreds of thousands of corrugations? There’s some pretty fancy aluminium wheels out there that look great, but ultimately suit a select group of people. If you are rock crawling every weekend a 2 grand set of wheels is probably not what you should be fitting! Get a set of cheaper steel ones that can be smashed back into shape in the unfortunate event that you damage one.
Is the tyre size legal?
There’s a lot of people running tyres on their 4WD’s that are too big, and that can easily and often make your 4WD illegal. If you know about it and still choose to run them, that’s on you, but I hate hearing from people who think they are all good, and are actually completely illegal.
Larger tyres can easily contribute to an accident, and if this happens your insurance company has every right to walk away without paying a cent, and that can leave you in a pretty nasty situation.
Will it do what we want it to?
Lastly, does the tyre and wheel package do what you need it to? There’s no point fitting hugely aggressive tyres that are way oversize if you just plan on mall crawling, unless that’s your thing!
Check the minimum wheel width and get suitable tyres
The takeaway is this; speak to your tyre shop before you commit to buying a new set of larger tyres, as they might not actually suit the wheels you’ve already got, or you are planning on getting and no one likes to deal with that!