How a Roof Racks Can Affect Your Car: The Effects of an Added Accessor

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Attaching any accessory outside the vehicle will ultimately change its shape, weight, aerodynamics, and dimensions.

All these will possibly alter the driving performance of the car. The roof rack could be more obstructive than others of all the items attached to a vehicle.

How will a roof rack affect your car?

The roof rack will easily affect the vehicle's handling, performance, and fuel economy. All that will be due to increased exposed areas to the strong outside wind while driving and a higher center of gravity. There is a vast difference between an unloaded and loaded roof rack and an empty or no roof rack.

Some effects of the roof rack are not substantial, and you will barely feel them as a driver, but there are those effects you may feel in specific driving situations.

Whether you want to transport that old sofa or bike to your camping place, installing a roof rack could be viable. It seems more practical since they come in diverse sizes and shapes and can be put on any standard car.

However, you need to understand the effects of a roof rack on top of your vehicle.

Effects of Roof Racks

Effects of Roof Racks

1. Reduced Fuel Economy

Many car owners complain about the fuel economy of their cars after installing roof racks. The car seems to guzzle more fuel than when it had no roof rack on top. Usually, that is because of the increased wind resistance on the road.

If you are having too much trouble with your fuel economy, you could look for more aerodynamic roof bars to reduce the resistance to the wind. An aerodynamic roof rack will reduce resistance between the strong winds and the car which will not overwork your engine.

2. Increased Noise

The other issue with roof racks is the added noise from the frames while driving. Usually, there will be a whistling noise from the roof racks. The faster you move, the louder the noise.

This whistle noise can be annoying, especially if you drive over long distances. Getting aerodynamic roof bars that will cut through the wind could be of some little help.

Aerodynamic roof bars will reduce this noise even though the whistle will still be heard. If the noise becomes unbearable, you could invest in a wind reflector to shield the roof racks from the excessive wind while traveling down the tarmacked road.

3. Height Restrictions

Installing roof racks on your car will increase its overall height. Even though this height may not be significant, it could give you problems in some circumstances.

Some car parks could have been made for exact car sizes and other restricted height areas. In such cases, having a roof rack could be problematic since you will not access the car park.

4. Performance and Handling

Adding roof racks to the vehicle will ultimately affect the car's performance, especially if the roof rack is fully loaded. Additional weight on the car could worsen the vehicle's handling and bring about movements during high speeds. However, the type of car you are driving and the load you carry will determine the performance and handling.

For example, a Mercedes GLS with a roof rack on top will not be affected in terms of performance, but a Volkswagen Polo with a heavy load on the roof rack can lose control during high speeds.

5. Potential Damage

Depending on the roof racks you have, some markings will be left behind where the racks clamp on. Even though this damage is not severe, it will leave some markings on the car.

To reduce any damage to the vehicle, consider looking for premium roof racks that come with padded clamps. The padded clamps will prevent markings on the car. You could also use car polish to rectify markings on the vehicle. If your rails are plastic, you could apply a black trim restorer.

Aerodynamic Drag

Effects of Roof Racks

A roof rack will not enhance your car's aerodynamics. Adding adjustments to the outside of the vehicle will affect the car's wind resistance. Typically, the roof rack will cause more wind resistance to the vehicle.

The frontal area of the roof rack will negatively affect your vehicle's aerodynamics due to the headwinds.

When carrying huge cargo such as bikes, you will expect more impact as more surface area is exposed to the wind.

The total magnitude of the effect will largely depend on the shape and size of the vehicle. It will also depend on the cargo carried and the type and size of the rack. The drag force can be calculated by:

Drag Force = Frontal Area x Velocity (squared) x Drag Coefficient x �

Drag Coefficient is typically how aerodynamic your vehicle is. A car is a big object moving via air, producing wind drag. Some vehicles could be more aerodynamic than other types having a drag coefficient of 0.3 to 0.4. Others, such as vans and SUVs, could have a drag coefficient of 0.5 to 0.6. Typically, that is because of the overall shape and design of the car.

Even though an empty roof rack does not contribute much to the drag coefficient, it has some footprints on the same. The same is also true when it comes to the frontal area, which is the area that is directedly exposed to the wind's direction.

If you have a loaded roof rack, the drag coefficient could drastically change, especially if you are carrying bicycles. You will experience 2 of three variables that are crucial for air drag that are negatively affected by your roof racks.

You can come across aerodynamic roof rack designs. Some of these racks will have a drag of about 10% compared to the high-drag models. However, you need to understand that wind resistance increases with velocity. Speed is your biggest enemy in terms of fuel economy and drag.

Fuel Economy With a Roof Rack

Roof racks will affect your fuel economy. They worsen the car's aerodynamics by increasing the drag coefficient and frontal area of the vehicle. 

That makes the engine work hard as it aims to achieve speeds and move against wind resistance. Drag will not sharply reduce with low velocity since it rises with an increase in velocity.

For example, an increase of around 20 mph could cause a double in the drag force from 50 mph. A reduction of 20 mph will cause a drag decrease of 66%. This kind of relationship between wind resistance and velocity is why speed has a significant impact on fuel economy.

With the vehicle moving faster, the engine will have to work harder to fight the wind resistance. While driving at 161 km/h, you can expect the aero drag to quadruple. That is why achieving speed in these less powerful cars is not as easy. Technically, your traveling pace has a massive impact on the gas mileage.

Empty Roof Racks

Many drivers always wonder whether an empty rack will affect the car's fuel economy. The answer to this predicament is quite simple. While moving at average speeds of 100 km/h in city traffic, no gas mileage is lost on an empty roof rack. When driving at higher speeds, expect the fuel efficiency to drop to around 15% from 5%.

That means an empty roof rack will typically increase fuel consumption in some circumstances. The footprint may not be noticeable while driving, but you will notice that when you visit the gas station.

Picking More Aerodynamic Roof Rack

Your roof rack's ability to cut through the wind determines how it will affect the car's performance and control. As mentioned earlier, an aerodynamic roof bar will have a massive difference in the vehicle's performance. These aerodynamic racks will cut through the wind with little resistance.

As much as they enhance the performance of your car, they will also reduce the whistling sound produced by the racks as you speed down the highway. An aerodynamic roof rack will help save on fuel economy, especially if you are traveling long distances.

Note that the aerodynamics aspect of the racks works perfectly when the frames are not loaded. If your frames are loaded with heavy bags on top, your luggage will reduce aerodynamics.

Will Racks Slow Down the Vehicle?

With some throttle applied to the car, the roof rack will slow you down because of the air drag generated. Your maximum speed is not achievable because of the same reason. For a vehicle with roof racks, the wind gusts have a wider surface area to impact and attack, which significantly slows down the car.

The presence of the roof rack will also impact accelerating, but again the impact will change based on the car's velocity. Accelerating from a stationary position will not have a significant effect, but accelerating to overtake another vehicle could be impacted by your roof racks.

Final Thoughts

While it is evident a roof rack will affect your car, you should know which conditions make the impact more severe. This guide has all that information and much more. You will learn the actual effects of roof racks on your car.  

About the author 


Vieira Babeker

Hi! I'm Vieira. I've always been interested in different Auto Accessories

My passion here at theroofboxes.com is to provide helpful straight forward clear advice and tips for Automotive Accessories.

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