How To Determine How Big of a Wheel My Car Can Take

Your wheel and tire choice is one of the most important pieces of customization you can do to your car. Wheels affect a lot more than just traction — fuel economy, acceleration, braking, and handling can all change when you make adjustments to your wheel weight and size, as I was recently discussing with my barber.

Recently, a predictable continuously variable transmission (CVT) failure took down my barber’s 2009 Nissan Murano. A 2015 Jeep Grand Cherokee (WK) took its place. So far, he’s loved the extra power and regular automatic transmission that the Grand Cherokee has over his old Murano’s droney CVT, but he’s ready for some mods. He had put 22-inch wheels on his old Murano, which he admits ruined the ride and were “a bit much.” But the stock 17-inch units on his Grand Cherokee are pretty dinky. Also, this time, he’s looking for more of an off-road performance setup, instead of the low-profile rubber band setup that was on his old Murano.

But researching online brought him to a series of dead ends and lots of forum threads with conflicting advice. Some said he could go as high as 22-inch wheels with fat tires without any consequence, while others made it sound as if the truck would explode if he increased his wheels by a measly inch. None of that advice answered his questions: Could I go up a wheel size without ruining my car? What will happen to my fuel economy? Well, this one’s for you Jamarr, here’s some information on what you need to know to safely go up in size.

There are two main measurements to consider when you’re looking to change your wheel sizes: how wide and tall of a wheel can fit in the wheel well without rubbing against suspension or steering members, and how much bigger or (smaller) the new wheel and tire combination is, compared to stock.

The answer to the first question is not always the easiest to find. Most OEMs would rather you not install aftermarket parts, aside from special sanctions that have likely been vetted thoroughly. It’s kind of a trial and error process of wading through YouTube videos and internet forums, but luckily Jamarr’s WK Grand Cherokee is a pretty common vehicle with thousands of owners who have already done the off-road legwork. In his case, the YouTube channel Emegos found that the Grand Cherokee will accommodate a 275/55/R20 tire without rubbing, at least on a wheel that looks to have the same offset as the stock 17 inches. Jeep forums back this up, and widely say a 32-inch (total diameter) wheel and tire combo is the max a Jeep Grand Cherokee can accommodate before rubbing.

Now, things can get complicated when wheel width and wheel offset are taken into account. A wider wheel with more negative offset would stick out from the body of the car, freeing up room, and allowing for an even wider tire, but probably not a taller one.

The second question is most crucial to the vehicle’s speedometer. The speedometer works by calculating speed based on tire rotation. A tire that’s substantially bigger or smaller than the stock size has a proportionately different circumference. Generally, anything beyond 3 percent or so in size difference will cause the speedometer to be way off.

Jamarr’s WK is currently riding on a set of 245/70/R17 wheels. Using the handy-dandy wheel calculator, he’s got quite a few choices in both the 18-inch and 20-inch categories that would give him more rim, but still have quite a bit of sidewall for a cushy ride, without destroying his speedometer’s accuracy. He also has some other choices, if he just wants to get the biggest tire in those wheel wells, speedometer accuracy be damned.

People often forget that wheel size and diameter are an integral part of a vehicle’s gearing. A wheel with a bigger circumference is, in effect, creating a taller gear ratio than stock, which would likely harm performance, causing the driver to maybe drive a little harder than before. Also, wider, squishier tires have way higher rolling resistance that will cause a vehicle to work harder against drag and friction, to go the same distance.

If I were Jamarr, I’d probably stick with something like a 265/60/R18 for an 18-inch wheel. In this tire size, the sidewall is still a nice and meaty 60 percent of the tire’s width, with no impact on the speedometer. Or, if he just wants a massive wheel, a 275/55/R20’s is about as big as he can go before he runs into any clearance issues. This tire size would be 4.6 percent larger than stock, necessitating a speedometer recalibration.

That was definitely a wall of text, but I promise, learning what size would be best for your new aftermarket wheel setup, isn’t as daunting as it sounds.

Generally, yes. Bigger wheels and tires are often heavier than stock, which means it’ll take more effort and braking force to slow down or accelerate. Then, there’s the gearing change that comes with a bigger wheel, as mentioned above. 

Typically, yes. Not only are bigger wheels often heavier and less maneuverable, but in the context of off-roading, a bigger, squishier tire will often have more sidewall than normal. Thus, the tire will be prone to more flex than stock, leading to lower on-road performance. Remember, Jamarr’s looking for a somewhat off-road-ish tire, so the compromise might be worth it here.

Generally, no. Sometimes wheels can be redrilled to fit a different bolt pattern, but that’s often outrageously expensive. Bolt pattern adapters do exist, but please be mindful that these devices often compromise safety. We here at The Drive would like to make sure our readers stay safe on the road.

The tire calculator is a great way to see the difference between your current wheel and tire setup, and the size you’re desiring. It’ll also show you recommended sizes that should be compatible with your vehicle.

As far as max size, that’s a little harder. It will take a lot of Google fu to find that answer. For most mainstream cars, it’s usually a forum or Quora question that’s likely already been answered years ago. For other less-common cars, finding your vehicle’s max size will likely be a series of trial-and-error. Bummer.

Happy hunting.