LOAD RATINGS
“A WHEEL load rating is the mass the vehicle must support on that corner of the vehicle, sometimes referred to as axle loading,” explained Helgeson.
“In theory, the mass distribution should be equal at all four corners of the vehicle – i.e. 50:50 mass distribution, so each wheel would need to carry 25 per cent of the total GVM,” he said. “However, mass distribution in 4x4 vehicles may have a 60:40 split, so the rear wheels may need to carry more load than the front wheels.
“To account for this we calculate the required wheel loading by multiplying the GVM x 0.3 which allows for a 60 per cent loading on one axle.”
Helgeson added that this is a rule of thumb and should be calculated accordingly if you have heavily modified your vehicle.
The consequences of not adhering to load ratings go beyond voiding your insurance or having a car that’s no longer roadworthy. Having an overloaded vehicle with wheels that aren’t load-rated to suit can put your life at risk, as well as others on the road.
“Consumers should be looking at the wheels load rating if specifically buying the wheels for off-road use,” said Allied’s Martin Tonkin. “A high load rating will help when putting your wheels through some serious 4x4 driving.”
MHT’S Corey Longstreth explained to us that a wheel’s load rating should not be exceed by a vehicle’s heaviest gross axle weight, divided in half.
“For example, if your vehicle’s heaviest axle weight is 4000lbs and the wheel you’ve selected has a load rating of 1500lbs, then you have exceeded the load the wheel can carry by 500lbs,” he said.
“While this might not mean immediate failure of the wheel, it can lead to a potentially catastrophic failure of the wheel that could have fatal results.
“Manufacturers will tell you to never exceed the load rating because extensive FEA analysis has determined that number is the maximum load the wheel can support failure of the wheel could occur and that could potentially create an accident on the roadway.
“If the failure of the wheel is determined to be the cause by police or insurance inspectors, denial of insurance claims could occur as well as any potential legal issues associated with the accident.”