Matching Tire Size With Wheelbase - The Long & ShortPosted in How To: Wheels Tires on January 27, 2014 Comment (0)
Building a 4x4 can seem like a never-ending cycle of trial and error. Just like hundreds of other DIY hobbies, there isn’t a definitive rulebook on how to be the ultimate 4x4 enthusiast, or better yet, how to build the perfect four-wheel drive. One of the best aspects of this hobby is the diversity of the vehicles and people who participate. One question we hear a lot is: “What is the ideal tire size for a given rig?”
More often than not, the answer has less to do with the vehicle, and more to do with what the user’s intentions are with the rig. Sure, most rigs look badass on 40-inch-tall tires, but if all you do is tow your boat to the river and hit the occasional muddy road to the hunting camp, the 40 doesn’t really make a lot of sense. Lift-to-tire ratio charts are a good place to start when matching up tires for your 4x4, but many of the charts come across as vague guidelines, not absolute answers. While a chart offers you an idea of what tire size your 4x4 could cycle, it doesn’t always answer the greater questions of what tire will work best for your axles, steering, and wheelbase.
Most stock light-truck and SUV axles can be good for up to a 37-inch-tall tire, but may require aftermarket components to compensate for the taller tires. Items such as higher numerical differential gears, stronger axleshafts, and even axle trusses will need to be factored in before you choose a new tire size. Larger, ¾- and 1-ton trucks tend to have stronger axles and more robust components, so going up to even a 42-inch-tall tire isn’t out of the question. Just as important as factoring in the axle’s strength, is making sure that your steering and brakes are up to the large-tire challenge. Moving a heavier and larger than stock tire can cause steering components to wear and fail prematurely. This can be compounded with rapid-suspension wear on some of the more frail independent front suspensions. Big brake kits, aftermarket suspension systems, and heavy-duty factory-replacement components can all make your rig handle the larger treads, but will be another investment you will need to factor in.
If there ever was an editorial can of worms, compiling a list of the right tire size and wheelbase is it. No matter how well thought out your formula is, there will be a way to poke a hole in the logic. Despite the lack of a one-size-fits-all solution, we’ve created four categories of some of the most common trail-friendly wheelbases offered in 4x4s. It should go without saying, but we’ll say it anyhow, this is simply a guide. Factors such as the vehicle’s lift height, type, and even the terrain it frequents can all play a part in what size rubber will work best for your machine. Have an opinion for which wheelbase and tire size combo you think is best? Be sure to join the conversation online at www.fourwheeler.com.
Wheelbase (in) 80-96
Tire Range (in) 31-37
If you fall into this category, then chances are you are piloting a Jeep Wrangler, CJ-5, CJ-7, Suzuki Samurai, Willys flatfender, or maybe even some oddball wheeler such as a Geo Tracker. Like it or not, your wheelbase is short, which isn’t necessarily a bad thing. A shorter-wheelbase 4x4 tends to be extremely maneuverable off-road, which historically has made them great for carving new trails across the nation. Aside from steep ledges, the nemesis of the short wheelbase for many years wasn’t so much the wheelbase, as it was the technology and way we used to overlift and overstuff the vehicles.
Nowadays, the low lift and big tire combo has increased the performance, handling, and overall driving characteristics of short wheelbase vehicles tenfold. A smaller/shorter 4x4 can sometimes avoid challenges that larger rigs face. A shorter wheelbase rig, when fixed with, say, a 35-inch tire, can also have an increased breakover angle over a similarly equipped rig with a longer wheelbase, so its propensity for hanging up on obstacles will be lessened.
Maintaining a low center of gravity will often require body modifications and bumpstops to run a larger tire, but the performance off-road will be worth the trouble. We’ve capped our tire range to 37 inches, as the overall balance and proportions of rigs in this category work best with this is and below.
Wheelbase (in) 108-117
Tire Range (in) 35-40
This wheelbase range is one of the most popular and one of our favorites. It brings in many of the fullsize and mini-trucks, along with the wildly popular Jeep Wrangler Unlimited. In this wheelbase range, the exposure of underbelly components or potential for damage to them is raised, but the maneuverability and stability that this length creates is excellent off-road. Items such as your driveshafts, gas tank, and powertrain oil pans become more exposed, especially in wheeling environments where large rocks and steep climbs are abundant.
Given that the breakover angle can be more complex (and lower) on a longer wheelbase, a 35-inch tire is the lowest we would recommend for more elevated wheeling. For more dedicated wheeling rigs, running 37- to 40-inch tires is extremely common and very effective for even more treacherous wheeling settings.
Wheelbase (in) 97-108
Tire Range (in) 33-38
Many of your midsize SUVs fall into this wheelbase category. Such popular rigs as the Jeep Cherokee XJ, Grand Cherokee, fullsize Chevy Blazer, and Ford Bronco are all part of the fold. As the wheelbase increases, so does the stability of the vehicle in climbing situations off-road. The necessity for a larger tire also becomes more important on the rig due to the distance between the front and rear wheels. The vehicle lift (height) and track width also plays a factor in the wheelbase/tire formula.
On the short side, we prefer at least a 33-inch tall tire. Moving towards the end of the 108 spectrum, we are fans of running up to a 38-inch tall tire. If you have the ability to keep the rig low, a 40-inch tall tire is not out of the question, but for the average 4x4, that’s a big investment, both from a financial and build standpoint. A more common, and somewhat happy medium, for this wheelbase is going to stay between 35 to 37 inches.
Wheelbase (in) 118 plus
Tire Range (in) 37 plus
Long wheelbase rigs can work very well on the trail, but they require a good driver and equipment that is up to the task. If you are wheeling anything over 137 inches, you’re most likely not squeezing through your average trail, so we’re going to leave the land yachts out of the equation. Long works great in expedition-style rigs and daily drivers—even purpose-built hillclimbers are great examples of where long and low work great off-road.
A 37-inch-tall tire is going to be a good start on the lower end of this wheelbase spectrum. The challenges of maneuverability and breakover angle will be increased significantly as the wheelbase lengthens, and this can only be compensated by tire size up to a point. In our Top Truck Challenge competition, we often see rigs well into the 120-inch-and-up range work well. They are often aided by 54-inch tires and rear steer, but those are just tools to get the job done more effectively.