Why do some trucks have a spare set of wheels hanging? Wouldn’t it better to just have all the wheels on the road?
In: 159
Those are cheater axels. You drop them to distribute the load across more tires. This reduces damage to the road, and you lift them with heavy loads to get better fuel economy
I think they call them cheaters because weigh stations check how much weight you have on each axel. This is regulated by the state to keep road maintenance down
Those wheels exist to support added weight within the trailer. When deployed they will also increased “drag” and, therefore, fuel consumption. While this increase may not be a large amount for an individual vehicle or trip, when you multiply that small number across an entire fleet, it becomes a sizeable amount.
Spoke with a fleet driver once about the aero skirts that are now prevalent on so many trailers. He said they were told it added roughly 1% to their fuel efficency. Now multiply that savings across a fleet of a thousand trailers. And there you have it.
In addition to what others have explained they can also be used to improve stability in slippery conditions by redistributing the weight balance of the truck. You can for example lower them extra low to increase weight on the front wheels to give them more traction to steer better. Lifting them will put more weight on the rear drive wheels (if the truck is loaded evenly) to give them more traction up hills and such.
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TIL that’s not where big trucks keep their spare tires. It’s a “drop axel” for heavy weight.
Thanks /u/blowingair ! Makes sense.
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