What It Takes To Run Big Tires
Photography by Harry Wagner
Big tires are awesome. It doesn’t matter if they are on a Samurai or a one-ton truck, we love the look of big, aggressive meats on our 4x4s. In order for them to work as good as they look though, you need to make some upgrades to your vehicle. Those include not only ensuring that the tires fit properly, but that your vehicle can still accelerate and brake effectively on the road and has the components necessary for the trail so the larger, heavier tires are not scattering parts. Below are the five first upgrades we recommend if you are running big tires.
Lower gears (numerically higher number) are necessary with larger tires in order to allow the engine to operate in the proper powerband. This is less critical with modern vehicles with eight- and ten-speed transmissions since there is a smaller change in RPM between transmission gears, but the ring and pinion ratio should still be matched to the tire size. If you go up 10% in tire size (such as from a 31-inch-tall tire to a 35-inch-tall tire) you should change your gear ratio by a corresponding amount (such as from 4.10 to 4.56). You may even want to consider going lower on the gearing (such as 4.88 in this example) to account for the increased weight of the tires and to provide a better crawl ratio on the trail.
Upgrading your suspension is an opportunity not only to fit larger tires, but also to increase ride quality, suspension articulation, and ground clearance. It is important to have a tire size in mind when shopping for a suspension, and consider factors like whether you are willing to trim body panels in order to fit the largest tires possible. Rubicon Express offers suspensions for Jeeps that not only provide improved clearance for larger tires but also increased articulation through the use of longer control arms and Flex Joints that provide a wider range of motion than rubber bushings. Larger diameter shocks are another worthwhile upgrade that help control the increased unsprung weight of heavier tire and wheel combinations.
Larger tires are inherently heavier than smaller tires, and they also provide more leverage. Think of a taller tire like a longer breaker bar on the end of a socket to put in perspective what they are doing to your braking system. Upgrades could be as simple as adding better brake pads from companies like Power Stop, or as complicated as swapping out rear drum brakes for discs from companies like G2 Axle & Gear. Installing larger diameter rotors and/or calipers with larger bores or more pistons is another option, with Teraflex, Wilwood, and Dynatrac all offering brakes for different applications. Just remember that the brake system is, as the name implies, a system. Calipers that need more fluid will likely require a larger master cylinder to move an increased volume of fluid through the same pedal travel.
Upgraded steering is critical to maintaining control not only on the pavement, but also on the trail. Airing down your tires creates a huge amount of stress on steering components, and the larger the tires the worse the stress gets. You can limit this by ensuring that you only turn the steering wheels when moving, but sometimes that can be a challenge in technical terrain. Upgraded tie rods and drag links with heavier construction, and larger tie rod ends, such as the Rock Jock Currectlync, are considerably stronger than the stock components. Steering boxes with larger sector shafts and pistons, such as the PSC Big Bore XD boxes for Jeep Wranglers, are stronger than stock and also provide more steering power, particularly when combined with a high flow power steering pump. The next step up is a hydraulic assist ram, which helps turn big tires when they are aired down on the trail, like the AGR Rock Ram. A ram requires a lot of fluid to operate though, so ensure that your steering pump can keep up and always match the throw of the ram to your steering box and steering stops to prevent breaking parts.
Fullsize Spare Tire
A full size spare tire means that you won’t be left walking home if you get a flat. The difference in diameter between tires on the same axle can create issues in the differential, particularly if you have a locking differential like a Detroit Locker. Related items you also need with larger tires include a jack capable of lifting your vehicle off the ground. The stock jack probably won’t get the job done anymore, but a taller jack such as a Hi-Lift or ARB hydraulic jack will ensure you can lift your big tires off the ground if you need to change one.
The Easy Button
If you want to get several of these upgrades accomplished at once, adding one-ton axles will net you not only stronger axles, but bigger brakes, better steering, and lower gearing at the same time. Currie, Dana, Dynatrac, and Teraflex all offer complete axle packages designed to bolt into Jeep Wranglers. If you have a different vehicle, you can still add one-ton axles, but custom fabrication might be required. While the cost may seem daunting at first, when compared to adding bigger brakes, lower gears, locking differentials, and trusses to your existing axles, aftermarket axle assemblies start to look very affordable.
Getting in and out of a vehicle can be a challenge, one that gets old when the vehicle is your daily driver or your hands are full. There are a variety of products to make this easier though, from retractable steps to grab handles. These products can make the difference between your truck being fun to drive and being a pain to get in and out of. If you have a complaint about your lifted vehicle, 4WP likely carries a solution to your problem.