Sunday, May 28, 2017 at 21:34
" Does the extra-cab section qualify as "seats". "
The seats, the extra cab area and the tray out the back all come under the heading of " load bearing areas ". If the car is to be loaded up to its maximum then each area must take its full share. Exactly how much must go in each area is a good question.
The engineers who designed the car will know how the load must be distributed right down to the last kilo. Dealers should be able to explain it to their customers. If they can't then contact the manufacturer or better still ask the dealer to do it for you. I have worked for new car dealers in my younger days. Ringing the manufacturer for a customer or arranging for a customer to meet the manufacturer's representative at the dealers was a normal part of the job.
Most owners tend to load their cars fairly
well but alarm bells always start ringing when things like slide-on campers or heavy weights on the tow ball come into it. Fully loaded slide-ons are notorious for overloading the rear end of cars and overloaded rear ends on utes in particular are notorious for bending chassis.
I went on a long Outback trip with about eight or nine other cars a few years ago.. One was a new extra cab with a superbly built custom made aluminium slide on. The roof tilted up at the rear and the bed was over the roof of the car. The rear end was too low so the owner lifted it first with heavier springs then air bags. All of these parts were readily available from aftermarket companies so the owner thought that was the right way to go and was not expecting any problems.
It did not bend its chassis that time but it did about twelve months later.
This link does not involve a slide-on but the result was the same
BENT C The owner of this car had carefully weighed everything that he put in the car. From memory it was about 200 kg under the maximum but look at what he had on the far end of it. There was 120 kg on the tow bar that had been slightly lengthened. Then there was the two spare wheels and their carrier hanging off the back. You then have to add whatever was in the back of the car behind the axle.
It was not weight that bent that car, it was a combination of leverage on the rear end plus mass and the forces generated by mass in motion.
Anything behind the axle is sitting on a lever i.e the distance from the axle back to wherever each object is. If you keep adding weight to the area behind the axle you would eventually force the rear end down so far the front wheels would lift off the ground. It is leverage that is doing that and you can't stop it by installing heavier springs or air bags.
Weight is just a measure of the pull of gravity. We see it as a figure on some scales. You can buy a kilo of something but you can't buy a kilo of weight.
Mass on the other hand is the amount of material in whatever is giving you a weight reading on scales. Your bathroom scales might take 120 kilos for example so if you placed a 120 kg block of concrete on them, they would read 120 kilos and no damage would be done to them. If you picked that block up though and dropped it onto them, they would most likely be smashed beyond repair even though the weight of
the block has not changed. The damaged has been caused by the material in that block falling and building up momentum then being brought to a sudden stop.
The same thing is constantly happening to the rear end of a car. As the front and rear wheels rise and fall suddenly, particularly on rough roads, the rear end of the chassis is constantly rapidly lifting whatever is sitting on it or stopping it suddenly when it falls.
That is the normal procedure for any car and the chassis or the rear axle housing will cope with it if it is within the design limits of the car. If it is not then things can and do break.
This is what you have to think about. You have to not only think about keeping the car within its weight limits as specified by the manufacture but you have to pay a lot of attention to where you place material in it. The forces generated by that material when it is in motion is the key to the whole thing.
Getting advice from somebody who understands all of this and is not trying to sell you something is the way to go.
Another thing to keep in mind is a tray back ute will roll off the assembly line as a bare cab/chassis with about ten litres of fuel in the tank. The weight of everything you add to it after that must come off its carrying capacity. That includes whatever body is fitted to it, like a flat tray or whatever, plus fuel, accessories, driver and passengers before you start loading the tray or the cabin.
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