If you own a mean off-roading beast like the Wrangler, I bet you’re already thinking about upgrading to bigger tires. First of all, they’ll look like a million bucks. Secondly, they will greatly improve your Jeep’s performance over bumps, steep climbs, rocky terrain, and more. Now, most experts recommend getting a 35-inch set. They have proven to be extremely capable over challenging trails.
However, there’s a catch: when it comes to tire sizes, the measurements aren’t always exact. That’s right: what you see at a local shop/online store in the specs doesn’t always mean you’ll get exactly that. Most likely, the size will be slightly smaller. So, how do you figure this out? What size is a 35-inch tire, actually? Join me, and let’s get to the bottom of this!
Advertised vs. Actual Tire Size
Ok, here are the facts: on the specs, or in ads, manufacturers always indicate the size at the maximum possible pressure. I’m talking about the PSI, of course (pounds per square inch). But, most drivers don’t go for max PSI, because it’s just counter-productive. Besides, for off-roading, it’s recommended to significantly drop the pressure, to maybe 50-60%, depending on the vehicle, the area, the actual tires, and other factors.
Say, for off-roading trucks and SUVs, 20-40 PSI is the golden middle. For the legendary Jeep Wrangler, 29 PSI for the front tires has proven to be the most effective setting. For the rear tires, go with 38 PSI – you won’t regret it. And now you see exactly why the tire size on paper almost never matches that in real life. Thus, if you bought a set of 35” tires, they’ll be somewhere between 33.5- and 34.5-inches.
For regular drivers, this isn’t a very big deal, of course. On the other hand, professional drivers should always keep this in mind to get the best results in competitive racing.
The Right Way to Measure Tires for the Wrangler
Alright, we just learned about the “tricks” that advertisers use. Now let’s see how we can properly measure any set of tires. In my experience, an online calculator is the best way to do this. When it comes to tires, we’ve got three different values. The width is measured in millimeters (from sidewall to sidewall) – it’s the first number you see. The aspect ratio, in turn, is measured in percentages.
This one’s a bit complicated. Say, if you’ve got something like 215/65 in the specs, that means the height of the tire equals 65% of its width. And finally, we’ve got the diameter – the size of the tire. In simple terms, it “tells” you the wheel size/diameter that the tires will fit. So, a 215/65/15 measurement on the sidewall means the tires will be perfectly compatible with a 15-inch wheel.
Figuring out the Exact Tire Size
There are lots of free online calculators that you can use. Simply type in the width, aspect ratio, and diameter, and you’ll see exactly how large the tire is in inches. However, even after you get the most accurate size, you still gotta consider what we discussed earlier. I’m talking about maximum and average PSI that people tend to use.
And remember: for a 35-inch tire, the width will, most likely, be somewhere in the 315-320 range. The ratio, in turn, will “hang” between 65 and 75 percent. With this info, it will be much easier to roughly measure tires at an auto shop off the top of your head. Or, better yet, launch that online tire calculator on your phone and see what’s what. I bet if the specs claim it’s a 35” set, when you check those three parameters, you’ll find that it’s 33-34”, not 35”.
What’s the Deal with the Numbers?
Is there a “P” sitting right before the numbers? That’s a US standard and indicates the tire is intended for Passenger cars. If there are no letters, that automatically means the tire was designed and crafted according to European standards. LT translates as “Light Truck”. And what about the “R” after the aspect ratio, you might ask? It stands for Radial and describes how the layers run (not very important for the average driver).
The “H” is a speed rating set by the tire manufacturer. With most brands, it means you’re not recommended to go over 130MPH/210KM/H. These aren’t strict requirements, but it would still be wise to check whether there’s an H rating on the tires, or not. Finally, the “DOT” indicates that the tires comply with all the safety standards in the US.