Are 33-inch Tires The Same As 285s (Metric vs. MM)

Are 33-inch Tires The Same As 285s? 285-wide tires are commonly referred to as 33” tires although 285 is the tire width in millimeters and 33″ is the overall tire diameter. 285/75/16 is usually the accepted metric equivalent size for 33” since it’s a 32.831″ tire diameter.

When comparing 33-inch tires to 285-wide tires, you are essentially talking about two completely different measurements.

The 33” refers to the width of the tire (285) multiplied by the height percentage of the sidewall (75), in millimeters, x2 because there are two sidewalls, divided by 25.4 (inches) plus the wheel size in inches (16”).

That’s a mouthful and a lot to digest at once so let’s break it down into a simple formula.

285 = the width of the tread in mm

Let’s now look into this in a bit more detail

As mentioned, 285 and 33 are referring to two completely different measurements.

Metric tire sizes can be a bit more complicated when it comes to understanding what size they are.

Let’s see what that means

Metric vs Millimeters

Because each tire manufacturer uses their molds, and there’s no set industry pattern, the 285/75/16 is usually the accepted metric size for 33s, even though the physical diameter of the tire can vary from manufacturer to manufacturer.

some are smaller than 33″ and some are larger, depending on the brand

Two different 285s can actually vary in true diameter.

Meaning some are smaller than 33″ and some are larger, depending on the brand.

This means 33-inch tires can be wider by 11 1/2 or 12 1/2 inches in width.

One way to find out the exact diameter of a tire is by going to the tire manufacturer’s website and checking the manufacturing specs on that specific tire and then comparing “apples with apples”.

Fitting 33-Inch Tires On Your Truck

Bigger, taller tires are the single most effective method of gaining improved ground clearance.

This is especially important for overcoming obstacles in an off-road situation.

There are however a few limitations, especially when it comes to IFS (Independent Front Suspension) 4WD vehicles.

Let’s now look at a few factors to consider when fitting 33” tires on your truck.

Lift Kit or Full Suspension

Before you even consider fitting 33” tires on your IFS truck, you’ll need to have a minimum 2” lift kit installed.

Depending on your truck, sometimes this isn’t enough, since you’ll still need to make additional modifications to prevent scrubbing at full lock.

• This is especially true if you want to retain full functionality and articulation which is important for off-road.
• If you decide to go 3” or higher, beware there are serious implications to any IFS suspension, but more on that later.

Who should fit 33” tires?

There are mixed opinions when it comes to large tire upgrades, and depending on who you ask, you’ll get differing opinions.

I give it a resounding YES!

I am currently running 33” tires on my Hilux truck and they work beautifully!

The added clearance, aggressive look, and improved traction and stability in my opinion are well worth it.

It comes at a price though.

Wheel Offset

Wheel offset or backspacing is a factor that gets little consideration, and it can create complications if you’re not sure exactly how much brake caliper clearance is required.

• It’s been widely agreed that 16×8 is the recommended option.
• The problem here is that you don’t want to go too negative offset on the wheels since you risk excessive wheel “poke”. (When the tires stick out of the fenders)

backspacing vs. Offset

Backspacing is the distance measured from the hub mounting surface to the inside edge of the wheel.

When you decrease backspacing, you gain more inside wheel clearance.

There is a fine line between keeping the tires in the guards and preventing scrub on arches, UCA, Brake calipers, etc.

Offset is measured in mm and generally refers to how your wheels sit inside the wheel wells.

You get positive and negative offset wheels.

When it’s positive the imaginary line is more towards the front and negative means the mounting surface is more towards the rear of the rim creating a deep dish effect.

Fender & Arch Trimming To Fit 33s

In many instances, there are a few plastic sections on the inner fender guards that need to be trimmed away since they will scrub at full articulation.

So get familiar with your Stanley knife and cutter and do some trimming of those wheel arches/guards where they are making contact.

Look out for the inner guard pinch weld and inside of the fender flare.

They usually need some trimming, depending on the tire and vehicle.

When you squeeze oversized tires into a wheel arch without lifting the truck, you’ll need to trim away a lot of the inside fender and arch plastic.

This will allow the tire to tuck behind the arch when turning and flexing off-road.

Will the 285/75/16 throw out your speedo?

When you upgrade from a stock tire to one with a taller aspect ratio (Sidewall), increasing the wheel circumference, your speedo can be thrown out.

In the case of 33” tires, the diameter will be larger and have an increase in the aspect ratio.

This might throw out your speedometer reading slightly.

The increase in tire circumference means the actual speed will be higher the faster you travel.  

The below table will give you an indication of how the speedometer reading is affected from 265/70/16 to 33”.

Speedometer reading	20mph	30mph	40mph	50mph	60mph	70mph	80mph	90mph
Actual Speed	21.4	32.2	42.9	53.6	64.3	75	85.8	96.5

Below are the actual differences between the stock 16” tire and the upgraded 285/75/16

Measurement	Stock Tire (265/70/17)	Upgrade (285/75/16)	Differences
Diameter	30.6”	32.8” (833mm)	+7.2%
Width	10.4”	11.2” (285mm)	+7.7%
Sidewall	7.3”	8.4” (213mm)	+15.1%
Circumference	96.1”	103.1” (2619mm)	+7.2%
Revs/Mile	659	615 (382mm)	-44

How Much Lift To Fit 33” Tires On A Ford Ranger

If you want to fit a larger 33” tire without a suspension lift, there is some modification needed.

The Ranger T6 crash bars protrude from the wheel well and the bigger 285/70/17 tire makes contact.

These will need to be removed/modified first so as not to damage the new tires.

They are quite a PITA to remove so be prepared.

Once removed, and a 20+ offset aftermarket wheel is fitted you should be able to get the 33” tires to fit comfortably.

How Much Lift To Fit 33” On A Jeep Wrangler

33-inch tires can be fitted to a stock Jeep Wrangler JK but with minimum clearance on the front bumper and not enough clearance for full articulation off-road.

Before running out and fitting bigger tires to your JK, make sure you understand all the implications and that other factors come into play such as backspacing, clearance, fuel economy, handling, and more.

To take full advantage of the Jeep’s legendary articulation, you would do well to fit a 3-4” lift before fitting 33” tires.

Big Lifts on an SFA Truck

When lifting any IFS truck, the front suspension configuration determines the complexity of the upgrade.

In the case of an SFA or LIVE axle, the axle is not physically attached to the chassis.

• The SFA live Axle allows you to fit big tires and higher lifts more easily.
• The CV angles are not compromised since they are always in line with the diff and axle. 
• This allows you to fit 3”, 4”, and even higher with fewer hassles.
• Fitting 33” tires to a Solid/Live axle truck requires fewer additional modifications and in most cases little to no Body or arch modifications.

Big Lifts on an IFS Truck

An IFS front axle on the other hand is a more complex process and you are limited.

Unfortunately, most 4WDs in production these days are IFS suspensions.

Manufacturers are more concerned about on-road performance and safety so they produce IFS trucks that appeal to a larger market.

The main problem with IFS suspension upgrades is the CV axles.

• The main problem with IFS suspension upgrades is the CV axles.
• The diff of an IFS truck is mounted directly against the underside of the chassis.
• This makes for excellent stability and cornering, however, it limits the downward travel of the wheels and places the CV joints under more stress when the vehicle is lifted too high.

NB: It’s not recommended to go higher than a 3-inch lift kit on an IFS vehicle, and if you do decide to go higher, you’ll need additional modifications such as diff drop kits, adjustable UCA (Upper Control Arms), LCA, and Stabilizer arms.

FINAL THOUGHTS

We have mentioned quite a few variables to consider before dropping a load on expensive oversized tires.

You should first determine what the primary application for the upgrade is.

Is it purely for aesthetics or will you need maximum practicality, and off-road ability, while maintaining maximum articulation?