Choosing the right 4WD tyres for your next adventure.
There are so many different tyre manufacturers, let alone the number of tyres to choose from. So how do you know which tyres are going to be best for you and your adventures?
The best thing to do would be to speak to a tyre retailer and they will sell you the tyres based on your answers to their questions.
Or they might just sell you the most expensive option.
You will need to ask yourself what type of driving you will be doing most of?
If the answer is 80% highway travel then you might be best to select something in a HT (Highway Terrain). These will give better handling at highway speeds, less noise when on road.
If the answer is I am not sure or around 50% highway and 50% off-road, then maybe an AT (All Terrain) tyre will be most suitable.
Most 4WD’s will come standard with a AT tyres as they are trying to provide the best of both on road comfort, wet weather handling and off-road capability.
If your answer above is 80% off-roading then you might be best to select MT (Mud Terrain) tyres. These will normally have a thicker rubber, so they will be heavier. But the thicker rubber will resist punctures better when off-roading better, they will also have large chunkier tread for better grip while off road. They can be noisy, but newer technology has found ways to keep the noise down, allowing you to get the benefits of extra grip off-road without the noise at highway speeds.
What size tyre can I install on my 4WD?
The first place to start is to find the tyre placard. This is normally a sticker that can be found by opening the front door of your car and looking on the body of the car between the inside and outside of the car, kind of behind the door.
They can also be inside the glove box, or can be found in the owners manual of the vehicle.
The tyre placard will give you details about the size of the tyre and the recommended tyre pressures, sometimes the placard will show different pressures depending on weight or speed of the vehicle.
The tyre size is a string of numbers shown similar to the following example:
225/70R16
The number is a combination of 3 main components.
The tyre tread width in millimeters. (225)
The ratio or percentage of the width of the tread to the height of the side wall (70)
The diameter in inches of the wheel or rim that the tyre needs to be installed on. (16)
The tyre placard shows what the car manufacturer’s recommendation for your model of vehicle, this takes into account many things including the suspension movement under full load and the movement requirements of the wheels during steering and braking.
There is also a legal requirement that will allow you to change from these details but only by a small amount. It is around 2 inches larger diameter which is 1 inch in sidewall size.
The amount can change depending on the state or territory that your car is registered in, weather you have had a suspension upgrade.
In the example above the overall diameter of the tyre can be calculated using a fairly complex equation. I have included this down in the additional information section.
My example
Theoretically I could increase the tyre size to 2 inches larger than the original of the tyre placard.
The original tyre size shows: 275/70R16, giving me a total diameter of 31.15 inches.
I could increase the size by 2 inches, or a total diameter of 33.15 inches.
This can be achieved either by increasing the ratio or increasing the tyre width.
The combination of both tread width and the ratio can either increase or decrease the overall height of the tyre. The overall tyre width is almost always wider than the tread width, especially on 4WD tyres.
For example:
305/70R16 this gives me a total diameter of 32.81 inches, an increase of 1.64 inches.
285/75R16 this gives me a total diameter of 32.81 inches, an increase of 1.64 inches.
These are just example tyre sizes, they are not meant to be a tyre size that is actually available. It is just showing that the same overall diameter can be achieved in different ways.
Keep in mind that as the tyre width and height increases, you are more likely to make contact with the frame or the mud guards of your 4WD. This can render a brand new tyre dead in a matter of only a few kilometers.
This could be where you might want to consider a suspension upgrade, which is usually a 2inch lift, this will give better clearance of suspension, mud guards and frame of the 4WD.
What I did
When choosing the tryes for my tow vehicle which is also my 4WD, I chose a tyre that was in between the MT and AT. The tyre I chose is also very quiet on the highway which I am very happy about. It is a Nitto RidgeGrappler
My tyre placard shows the original tyre size of: 275/70R16 this gives the tyre diameter of 31.15 inches.
I chose to go to a tyre size of 265/75R16 this gives my a tyre diameter of 31.64 inches.
While this has not increase my diameter very much it has increased the width of my tyres and this does not rub on my frame or mud gards either.
My spare tyre on the back door only just misses the body of the car.
When purchasing my caravan, I was happy to find out that the wheels from my Patrol and the caravan are able to bolt straight onto either the 4WD or the caravan allowing them to be swapped around as required. This gives me an added advantage for remote travel, allowing me to have 2 punctures and still be able to continue on.
The same was true for my camper trailer, but now that I have increased the tyre size on my Patrol the clearance on the camper is very small, meaning that while the wheel will bolt onto camper I will need to go very slow to avoid the tyre rubbing on the mud guard.
But I can still put a wheel from the camper trailer onto my patrol.
Additional information
To find the diameter of a wheel and tyre together:
Diameter of a circle is D.
We can find the diameter of a wheel and tyre by adding the diameter of the rim and adding the height of the sidewall at both sides (top and bottom) or (left and right) to measure the overall tyre.
If we use the same as the example above for the tyre size.
225/70R16
The height of the side wall in mm can be found by taking the tread width 225 and multiplying by the ratio or percentage 70 and then dividing by 100.
We then need to convert this to inches by diving by 25.
So we get 16 + 2 x the height of the sidewall of the tyre.
We get the height of the side wall in mm to be: 225*70/100=157.5mm
We need the height of the sidewall in inches we we take 157.5 and divide by 25 this equals 3.94 inches.
So D for the example above equals the 16 + 3.94 + 3.94 = 27.88 inches.
Make sure to substitute the numbers on the side of your tyre to get your diameter.