You’ve seen trucks driving around and did a double take - why do trucks have dual rear tires? What utility does this have?
Dual rear tires can be hard to understand without knowing about towing or load capcity. It’s also something a child might ask you that you don’t quite know the answer to.
The purpose of dual rear tires on a truck comes down to safety and towing. With dual rear tires, the weight of a big item in the bed or being towed can be distributed more evenly. Believe it or not, the tire setup actually helps with traction and turning.
But how does that work? Shouldn’t having additional tires make a turn more difficult? We’ll further explain a bit more about how trucks like these work when they are towing, and why “dually” rear tires are helpful.
There is plenty of research material on the Internet about why some trucks have dual rear tires. We also have a bit of an education and experience with towing, so we know first hand how much driving changes with carrying a load.
What do dual rear tires do?
Let’s start by shortening dual rear tires to more commonly road terminology - a truck with dual rear tires is often called a “Dually.”
Not often for appearances
Some say that people put dual rear wheels on a truck for appearance purposes. This might be true in a few cases, but there are some drawbacks to putting two wheels on the rear axle that make it not among especially common cosmetic changes to a truck.
Handles more weight
A dually can handle more weight in the truck bed and on the tow hitch than a standard truck. In the case of a new Chevrolet Silverado 3500HD with the big 5.3L 8-cylinder engine, or even the 6.2 liter 8-cylinder engine, there is still a limit to what the truck can tow or haul. With a stronger rear axle and two sets of wheels on each side, you can put more than a ton more in the truck bed, and tow more than 5,500 pounds more.
For a person who is hauling things back and forth to worksites, or traveling with a big trailer - possibly with livestock or horses - the amount of weight either results in having to make multiple trips, carrying less, or leaving something behind.
Drivers who haul large items - and we mean large items - like heavy power equipment, cows, horses, etc, need to be able to consider the weight of all the things they carry. A vehicle can only carry so much weight before it starts to need additional tires to get more traction. Or before the vehicle becomes like a semi.
Better traction and stability
A dually gets better traction with four wheels in the rear, which is great when towing a large amount of weight and needing to turn or manuever. Extra weight makes a vehicle more difficult to control, especially when sudden braking is needed. Duallies can make the often times uncomfortable experience of slowing down with a trailer or a load of shingles more easier - and safer, because the tires offer a wider stance that will cause the truck and trailer to sway less.
Notice how your car or SUV drifts a little under windy conditions? Imagine the same thing when carrying a large load behind you. This can be a little scary. The distributed weight from a dually truck can help with bad weather and wind.
Any downsides to a dually?
Duallies are helpful for many things related to towing and hauling, but they offer some drawbacks too.
A truck with a longer, more supportive rear axle. A dually can cost between $1000 and $2000 more than a regular truck. Also realize we are not talking about your average road truck. We are talking about a heavy duty truck, often with fewer amenities for the price.
Naturally, with more tires, you’ll also expect to pay more for replacing and rotating 6 tires instead of 4. To many people who own a dually, the prices are objectively worth it because of the value of the equipment or animals they are hauling.
While duallies certainly offer an advantage while you are towing, they also make driving in the city more difficult. A dually has a wider turning radius and sticks out more - requiring a bit more attention to spacing when driving through smaller streets.
With more weight from a larger axle and more tires comes lower fuel economy. This can be seen as a disadvantage just from a cost standpoint. Most large truck and dually owners know that they shouldn’t expect to get SUV or sedan gas mileage while towing and hauling.
Less comfortable ride
Duallys are not known for their ride comfort. Additional rubber on the pavement doesn’t make for a smooth or clean ride. In the case of a dually, the driver is willing to sacrifice a dreamy, cloud like ride for the purpose of being able to haul more.
For some newer trucks, manufacturers are aware of the comfort issues and offer more robust suspensions and comfier seats for the purpose. You’ll spend more on trucks like this - but it can be worth it if you are hauling a tractor hundreds of miles per day.
Could you put dual wheels on the front?
Putting dual wheels on the front would make a vehicle difficult to manuever. In the case of a dually, the truck is also most a rear wheel drive or four wheel drive vehicle.
Dual wheels are only especially helpful when placed on the rear axle. When a four wheel or rear wheel drive dually begins to produce torque, it’s transferred to the rear wheels first, where the group of four tires can be the most effective.
Front wheels wouldn’t help because they aren’t placed close enough to the payload or the trailer and hitch to help move the weight.
Does a dually cause additional wear and tear?
Trucks with the capability of using four tires on the rear are also built for the purpose. They have a longer, stronger axle both for additional tires and to turn under more stress.
Could you make a single rear wheel drive vehicle into a dually?
You could if you know a lot about trucks and have some serious mechanics equipment.
How much can a dually tow?
This depends more upon the vehicle. Some heavy duty trucks can tow upwards of 14,000 lbs or more. You should rely more on what the owner’s manual says about whats called the Gross Vehicle Weight Rating, which refers to the overall capacity of the truck, and includes people and their things. A truck owner should be careful not to go past the capacity designated by the truck to avoid problems with the truck body and transmission.
Do duallies need particular tires?
The tires on a dually are based more on the purpose of the truck, and the size needed. You’ll need matching rear tires, of course. A dually driver might have all season or all terrain tires on - it’s really up to where they are driving and how. There is not a specific category of tire for a dual rear tired truck though.
About THE AUTHOR
I've spent many years selling cars, working with auto detailers, mechanics, dealership service teams, quoting and researching car insurance, modding my own cars, and much more.Read More About Charles Redding