Forum Discussion
kohldad wrote:The phenomena is a resonance between the vehicle inertia and its suspension, that shock absorbers can't stop.
Bingo. Regardless of frame flex, under loaded, over loaded, etc.
Assuming it's not just a way overloaded truck and the truck doesn't have worn out shocks, there are three easy things to do.
Change shocks, preferably to an adjustable shock so different settings can be tried. This will change the harmonic frequency.
Change you speed to adjust the rythem of the tires and road irregularities.
Change you COG by shifting weight forward/aft in the camper. This will change the loading on suspension components which will result in a change in the harmonics.
Even my rig which is 1,600#s under payload experience porposing at times, especially on concrete roadways and bridges. I just change speed to get away from the harmonic frequency of hitting the joints and the problem goes away.
NO BINGO. The understood DEFINITION of porpoising with regard to truck camping is that the cabover moves significantly with respect to the cab. If not, then Lance struts would be worthless. But the Truck Camper Magazine test and personal experience shows that they DO have a positive effect. And since they attach near the corner of the windshield, the purpose has to be to dampen the frame flex that causes the cabover vs cab relative motion.
With my new truck, the frame flex is gone. When I hit rough bumps or harmonic frequency joints, the suspension reacts but the frame does not flex. That can be uncomfortable, of course, but it is not porpoising.
I agree that slower speed and, to a minor extent, internal weight shifting may help. Changing the harmonic frequency by adjusting the shocks just means that some other joint interval will come into play.
Rick
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