Quick answer: Truck tire sizes come in two formats. Metric looks like 285/70R17 — width in millimeters, sidewall ratio, and wheel size. Flotation looks like 35X12.50R17 — overall height, width, and wheel size, both in inches. When people say "33s" or "35s," they mean the overall tire height in inches. A 285/70R17 is about a 33; a 35X12.50R17 is a 35. Here is how to read either one and figure out what fits your truck.
Tire sizing looks like a secret code, and it trips up almost everyone planning their first build. Once you can read it, the whole thing makes sense.
The Two Formats
Every truck tire is written one of two ways, and you will see both when you shop.
Metric (P-metric / LT-metric): 285/70R17
This is what most trucks come with from the factory. Reading it left to right:
285 — the tread width in millimeters.
70 — the aspect ratio: the sidewall height is 70% of the width. A lower number means a shorter sidewall.
R — radial construction (basically all modern tires).
17 — the wheel diameter in inches the tire mounts to.
You will often see "LT" in front (LT285/70R17) — that means Light Truck, a tougher tire built for load and towing, which is what you want on a truck.
Flotation (high-flotation): 35X12.50R17
This is the format built for the lifted-truck world, and it is easier to read because it is all in inches:
35 — the overall tire height (diameter) in inches.
12.50 — the width in inches.
R17 — radial, on a 17-inch wheel.
So What Are "33s" and "35s"?
When people say 33s or 35s, they are talking about the overall height of the tire in inches — nothing else. It is the shorthand the whole truck world uses.
The confusing part: a metric size does not tell you the height directly, so you have to convert. A rough way to do it: take the width in mm, multiply by the aspect ratio, that gives sidewall height in mm; double it (two sidewalls), add the wheel diameter, and convert to inches. Or just know the common ones:
A 33 is roughly a 285/70R17 or a 33X12.50R17.
A 34 is roughly a 285/75R17 or a 295/70R18.
A 35 is roughly a 35X12.50R17 or a 325/60R20, depending on brand.
Sizes vary a little between manufacturers, so a "35" from one brand might measure 34.6 and another 35.2. That matters for fitment, which is why we measure rather than assume.
Quick Estimate
What This Means for Your Truck
Tire size is the single biggest decision in a build, because it drives everything else — how much lift you need, whether you will rub, whether you need upper control arms, and whether your gearing still feels right.
33s are the sweet spot for most trucks: they fit with a modest level or lift, usually with little or no trimming, and they do not hurt your gearing much. 35s are a bigger commitment — more lift, sometimes trimming, and you feel them in acceleration and towing. We go deep on this in best tire size after a leveling kit and 33 vs 35 tires.
Width and Offset Matter Too
Height is not the whole story. A wider tire (that 12.50) needs the right wheel offset or it pokes past the fender and rubs. Getting the height, width, wheel offset and any trimming right together is the actual skill — a tire that is technically "in spec" can still rub with the wrong wheel. We cover the wheel side in our wheels and tires guide.
The Easy Button
If you would rather not do the math, our tire size calculator converts between formats, and we mount and balance in-house on every build. Tell us the truck and the look you want, and we will spec the exact size and wheel that fits without rubbing.
Get the Right Size the First Time
Tire mistakes are expensive — a set that rubs or wears wrong is real money. Tell us your truck and your goal and we will get the size right before anything is ordered. Get a free estimate or call (936) 320-8120. Willis, TX — serving Conroe, Montgomery, The Woodlands, Huntsville, Spring and Tomball. Browse our wheels and tires or see recent builds in the gallery.