True to Size
The first thing we need to discuss is the fact that not all 35- and 37-inch-tall tires are actually true to size. In fact, nearly none of them are. It’s just the size the manufacturer rounds up to. If you want to see how tall (and wide) the tire truly is, you’ll need to look at the manufacturer’s specifications for that specific tire. There, you will find the true size listed. This sizing variation is often why one tire may rub when another does not.
Before you close out that spec box on the manufacturer’s website, take a look at how much the tire weighs. Just like sizing, tire weights will range between different companies. In general, a 37 is going to weigh more than a given 35. This additional weight is going to impact the vehicle’s performance. The heavier the tire, the bigger the blow to power, fuel economy and braking. There are ways to combat these effects that we will discuss later in the article.
The primary benefits of moving to a taller tire are to increase ground clearance and traction on the trail. The larger the tire, the more ground clearance you’ll gain. Simply put, every inch counts off-road. While 2 inches may not seem like much, on the trail it can make a world of difference. When you couple in the longer wheelbase of the four-door Wrangler, the large tire becomes even more important.
Power and Fuel Economy
The eight-speed automatic in the Jeep Wrangler JL makes moving up tire sizes much less of detriment to the powertrain. That being said, no matter which size you move up to, you will notice a hit to your power and fuel economy. An easy way to combat this is by installing a higher numerical differential gear ratio. On the Xtreme Recon package from Jeep, they are placing 4.56 gear in Jeeps equipped with automatic transmissions and 4.88s for those with manuals. This is for Jeeps running a 35-inch-tall tire. A taller tire will require even more gearing. If you don’t re-gear with a 37-inch-tall tire, you’ll likely notice that the Jeep will no longer hold overdrive gears on the highway very easily. If you have a Rubicon with 4.10 differential gears, this won’t be as much of an issue if you are running a 35-inch-tall tire.
Moving up to a taller tire will require additional lift in most cases. Thankfully, the massive wheel wells make it where just a modest amount of lift can make this happen. Rough Country offers a variety of suspension kits for the JL ranging from 0.75 inches all the way up to 6 inches. Your tire size goals and how intended on using the Jeep will greatly impact on which suspension is the best fit for your Jeep.
There’s no question that a 37-inch-tall tire simply looks great under the JL. However, it will make a greater impact on the vehicle overall. A 35 in many respects is a more practical solution and will still give you plenty of performance benefits on the trail. If you have questions which upgrades are needed to give your JL a better stance and performance for the trail, be sure to give us a call at 800-222-7023.