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Ground pressure per wheel set?

Ground pressure per wheel set?

(OP)
I am looking for either guidance or a formula for calculating ground pressure per wheel set for a truck and trailer that has a capacity up to 80,000 lbs. The tandem axle capacity for both front and rear is 34,000 lbs each and the capacity for the front steering axle is 12,000 lbs. Thank you.

RE: Ground pressure per wheel set?

I don't understand the question. If the truck is loaded to capacity and the weight distribution is correct then the ground pressure is 6,000 lbs per front wheel (12,000 / 2) and 4,250 lbs per wheel in each tandem set (34,000 / 8).

The suspension design in the tandem axles is normally designed to evenly distribute the load between the two axles, and the side-to-side distribution is the operator's responsibility to load the truck correctly, and a good many transport trailers have the ability for the trailer's tandem axle to be shifted fore/aft to get the weight distribution right, in addition to the operator's responsibility to load the truck correctly.

RE: Ground pressure per wheel set?

(OP)
Thank you. I am reading between the lines of a scope of work that I am quoting for a potential customer. None of us in 30 years rigging, trucking and mechanical engineering have ever heard this particular term (ground pressure per wheel set). They specifically asked for the capacity of each truck and ground pressure per wheel set. It seemed too obvious, that they would be asking for equal weight distribution on each wheel since the capacity is already known. I was wondering if they were looking for pounds per square inch of each of the set of tires footprint. I was hoping someone had actually heard this particular term-(ground pressure per wheel set.) Or that there was a formula for converting truck tire footprint to psi when under a full load. Thanks again.

RE: Ground pressure per wheel set?

The 5th wheel location on the tractor can also be tweaked a bit fore/aft, again as a means of managing load distribution.

Don't overlook lateral load transfer due to cornering and longitudinal load distribution due to braking or acceleration.


Norm

RE: Ground pressure per wheel set?

You need to ask the customer for education about what they mean.

It smells like they don't know the difference between pressure and force.

Mike Halloran
Pembroke Pines, FL, USA

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