Whispbar, Pro-Rack and Yakima Load Ratings

Whispbar, Pro-Rack and Yakima Load Ratings

RACK TECH EXPLAINED

Applicable to all Whispbar, Yakima, Yakima LockNLoad Crossbar and Platform load carrying systems.

Confused by how much weight you can actually carry on-top of your vehicle? Don’t worry, a lot of us are, but this helpful guide should help you calculate this.

If still in doubt, please drop us a line on 08 82606433 or by our online contact form and we will walk you through this.

When trying to calculate how much weight you can carry on top of your vehicle there are few key factors to take into consideration:

  • Load ratings
  • Static vs dynamic forces
  • On-road vs off-road usage

CALCULATING LOAD RATINGS

To calculate the load rating of your vehicle’s roof, you first need to understand that in order to do this you need to know the ratings of the various components that your vehicle will be carrying.

A typical Yakima LockNLoad roof carrying scenario consists of:

  • A vehicle
  • A crossbar solution, typically consisting of crossbars, legs and a vehicle specific kit.

OR

  • A platform solution, typically consisting of a platform, then either legs and vehicle specific kit or RuggedLine mounting system.
  • Possibly a further carrying accessory like a roof box, kayak holder, boat loader, bike carrier etc…

Each of the items listed above has an independent maximum product load rating. The maximum amount you can carry on top of your vehicle is the lowest maximum value of any of these elements.

Product Load Rating, this is referring to the maximum permissible load that can be supported by the roof rack product. Generally this is a higher load rating than the actual load you can carry on the product, on your vehicle.

Many factors need to be taken into account with these load rating figures:

Example: A roof platform may have a product load rating of 150kg and the mounting structure and/or legs have a load rating of 80kg – therefore the overall load rating of the product is the lowest number 80kg.  The conditions of the dirt road you are travelling has an impact that will also reduce the load rating. Always consider the load rating as the lowest of the values.

If the lowest number identified relates to the vehicle roof, remember that the load rating includes the crossbar or platform system weight. So, if your crossbar solution weighs 10 kg, the maximum you can carry on the crossbars is 70 kg (80 kg – 10 kg = 70 kg)

To find the load ratings of the various components you’ll need to consult the manufacturer’s instructions (owner’s manual for the vehicle roof rating) and/or website. Yakima LockNLoad product load ratings can be easily found on your local Yakima website in the LockNLoad section and your vehicle’s specific info on our fit finder. If in any doubt, contact us for further clarification.

Always remember that load ratings for systems assume that any load is evenly spread over the system. Where possible, apply this when loading your vehicle. Excessive loading on a point can cause damage and vehicle instability.

STATIC VS DYNAMIC LOADS

Dynamic is when you are driving your vehicle and there is motion.

Static is when your vehicle is stationary.

The load ratings applied to products by roof rack manufacturers are for when you are driving the vehicle. These are dynamic load ratings. Static load ratings are generally higher.

Why does this matter? 
Well, generally it doesn’t, as you don’t add more luggage when you reach your destination and stop driving.

Where it does come into play, for example, is with roof top tents (RTTs). In the example above, we determined that you can carry 70 kg on your crossbars. If your RTT weighs 50 kg, you are within your limits by 20 kg (70 kg – 50 kg = 20 kg).

So, what happens when you climb into your RTT? If you weigh 80 kg, using the dynamic load rating, you would naturally be well over the limit. Don’t worry though – unless you plan on being in your tent while driving (which is not recommended)! This is when the static load rating applies.

As a general rule, in a static environment, the load rating can be increased by a multiple of three (3). So, in this case, you can load 230 kg: 80 kg x 3 = 240 kg – 10 kg (roof racks) = 230 kg (remember, this needs to be evenly distributed) onto your roof and you will be ok and actually have 100 kg to spare.

(230 kg – 50 kg rooftop tent – 80 kg person = 100 kg)

Note that the 3x multiple applies to roof rack components. As a general rule, it should be applicable to most vehicle roofs but we always recommend you consult with your vehicle manufacturer before assuming any increase from dynamic to static load rating in the vehicle roof.

Static loading is the rating applied when the vehicle is stationary.

OFF ROAD USE

All load ratings are applicable for driving on well-formed sealed roads with a smooth surface.

Once you move to forest service roads, access roads or other non-technical terrains that are not smooth surface roads at moderate speeds, your stated load ratings have to be reduced. This is because the extra bumpiness of these environments gets transmitted through the vehicle and anything attached to it, potentially generating additional forces on your roof rack system.

For Yakima LockNLoad off road rating reductions across specific roof rack systems, refer to the table below via the Yakima website:

So, in the example previously mentioned where it was determined the roof capacity at 80 kg was the weakest link, if the crossbars are attached via a track mount system the 80 kg will reduce by 20% to 64 kg (remember to then still deduct the crossbar or platform system weight to determine how much you can carry i.e 64 kg – 10 kg = 54 kg).

* Note: extreme four wheel driving such as rock crawling are not covered by Yakima’s warranty regardless of fit type.

ALTERNATIVE MOUNTING OPTIONS

Not attaching the roof racks to your vehicles roof? Don’t worry, in general, the same rules apply.

If you’re attaching your roof rack solution to any of the following:

  • Ute tub
  • Ute tray
  • Ute hard lid
  • Canopy

The same guidelines apply for calculating the maximum load you can carry and off road weight reductions of Yakima’s roof rack systems.

However, you need to speak to the manufacturer of the vehicle, tray, hard lid or canopy to understand whether they have their own off road rating reductions and dynamic to static load increases, as this is likely to vary by brand and manufacturer.

Then, always remember to apply the lowest rating.

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