If you own a large vehicle, such as a jeep or a pickup fitted with 33-inch tyres, chances are, you have come across the 285s, especially if you have planned on putting a set of this tyre type on your vehicle. Whether you want to upgrade your tyres for the sake of aesthetics or to provide the off-road capability to your pickup, you should know the difference between 33” and 285 tyres.
A 33-inch tyre is considered the same as a 285 one, scale-wise. That’s because while a 33” tyre is the entire diameter or height of the tyre, 285 is the measurement of the tyre’s treads in millimetres.
There’s some minor computation involved here. However, you have to consider the numbers involved first, which are the markings on the sidewall of your jeep or pickup truck.
Typically, the markings on a 285-mm tyre size differ, depending on its total scale. For this example, however, you have a tyre with the markings 285/75/16 on the sidewall.
The first combination, 285, refers to the tread width, while 75 is the percentage of the sidewall height in millimetres. In this case, the equation will appear as 285 mm x 0.75mm = 213.75 mm.
Since there are two sidewalls, we multiply the answer, 213.75 mm by 2; thus, with 213.75 x 2 = 427.5 mm. Divide the answer, 427.5 mm, by 25.4 to convert the measurement to inches. For this matter, you will have 16.831” as your answer.
Then add the answer to 16” (which is the diameter of the rim of your vehicle). So, with 16.831” + 16”, you will have 32.831”, and that’s the final answer. In this case, 32.831”, or 33” when rounded off, refers to the approximate diameter of your tyre measured in inches.
How Much Is the Difference Between a 33” Tyre and a 285 mm Tyre?
There are no two tyre manufacturers that produce the same tread patterns. That’s how you can easily distinguish one tyre from another. However, you may not notice the dissimilarities in size despite the slight discrepancies between a 33-inch and 288-mm tyre. For the curious and meticulous types, we have done you the favour of knowing how much difference there is between the two tyre sizes using the table below:
|Diameter—inches (mm)||32.83 (833.9)||33.03 (838.88)||0.2 (4.98) 0.6%|
|Width—inches (mm)||11.22 (285)||12.52 (318)||1.3 (33) 11.6%|
|Circum. —inches (mm)||103.14 (2619.77)||103.76 (2635.42)||0.62 (15.65) 0.6%|
|Sidewall Height—inches (mm)||8.42 (213.75)||8.51 (216.24)||0.1 (2.49) 1.2%|
|Revolutions per mile (km)||614.31 (381.71)||610.66 (379.45)||-3.65 (-2.27) -0.6%|
As you can see, there isn’t much difference between the two tyre sizes. In fact, the percentage values that you get in terms of the diameter, width, and circumference on both tyres, whether in inches or millimetres are considerably small. If there are, it’s so minimal the replacement tyres would not even create any inconvenience to you or your vehicle.
What to Consider Before or When Upgrading to a Sized Tyre?
If you want to replace the tyres of your vehicle for improved aesthetics or off-road capability, you don’t just rush to a tyre centre and have those 33s or 35s fitted into your pickup. There are just some crucial things that you take into account. The factors that may help prevent your vehicle from running into issues that may affect its performance are as follows:
Wheel Offset and Backspacing
A wheel offset refers to how the wheels are fitted into the wheel well of a vehicle. Because of the varying designs concerning the placement of the hub, there are three different types of offsets. They are zero, positive, and negative wheel offsets.
A zero wheel offset occurs when the wheel of the hub is aligned with the wheel’s centreline. Meanwhile, when the hub is situated at the front of the centreline of the wheel, you have a positive wheel offset. Conversely, a negative wheel offset happens when the hub is behind the wheel’s centreline.
If you want to install a new set of tyres, say, 285 or 33s on your pickup truck, you should note how far the hub of the wheel is from the wheel wells. In this way, you will not have any clearance issues when the wheels articulate. When the tyre touches the parts located at the wheel well, this is called backspacing. To avoid any backspacing concerns, choose a wheel that has the proper wheel offset. In the case of a larger tyre like a 33”, a negative wheel offset may help prevent tyre performance problems.
Inner Fender Liner
Before you have that wide 258s or 33s fitted into your wheel wells, make sure that there is sufficient space between the inner fender and the tyre itself. The inner fender, or the fender liner, is the part of the vehicle that protects the components inside the wheel well from dirt and corrosion.
Vehicles with insufficient allowance between tyres and their inner fenders may encounter suspension problems in the long run. Also, you may experience handling problems because there may not be enough headroom for your tyres whenever you make maximum articulation, especially off-road.
Wheel offsetting and resolving inner fender issues come together in this case. For that matter, selecting a wheel with the proper offset can keep you from running into such a problem.
Lift Kit Suspension
Installing a lift kit suspension under your jeep or pickup gives it an additional clearance between the tyre and the wheelhouse. Lift kits make ideal complementary equipment if you are planning to switch to larger tyres, such as a 33” or 35”, especially if you want to go off-roading.
The kit usually consists of strut spacers, which may range from 2” to 4”, as well as coil springs and lift blocks. Depending on the type of struts installed, the lift kits provide that extra space around the tyre, which prevent the tyre shoulder from scraping against any of the components in the wheel well or the fender liner. Consult the expertise of a tyre specialist if you have questions on how much lift you should give your vehicle.
It’s evident that tyres come in different shapes and sizes, thus knowing the type of tyre that fits into your vehicle may help a lot, especially if you are doing this for reasons of practicality or rugged appeal. Apart from that, you also experience optimal functionality of having the ideal tyres for your pickup, without compromising your car’s overall performance.