Pickup truck tow vehicle stability tests

AH64ID wrote:

Arcamper wrote:
This topic really surprises me that anyone who has ever towed heavy would say 4 rear wheels are no better than 2. I just did a test myself out in our company parking lot. Parked my 3500 DRW next to a coworkers new 3500 SRW. Put my hand on the bed pocket above the rear wheel and pushed hard on both trucks. The SRW truck I could push about 3/4 inch back and forth. My DRW I could not move at all. It was all in the tire sidewall so I thought maybe his tire pressure was lower. Mine are at 65 and his were 70. After this controlled test I realized a DRW is more stable than a SRW of the same make and year.(How's that for scientific) LOL

While the suspensions on the two trucks should be the same, assuming not a lot of weight in the DRW or suspension enhancements there is something not right about that test.

DRW stability compleatly aside, I have a very hard time believing you can quantify the difference in tires and suspension and get 3/4" of tire squish (a tire rated for at least 3500lbs with 87% of its air) by pushing on the stake pocket.

I can put 2000lbs in my bed and not get 3/4 of tire squish, and I am doubting you are putting 1000lbs of load on a stake pocket with your hands and not moving the suspension.


Yes a DRW is more stable, but not for the reasons man think. The analogy about standing with your feet spread is pretty useless in this situation. Here is a way to test that it's useless with a floorjack and a pair of Jack stands. Jack up the rear off a DRW and put the jackstands under the springs, and apply a known force to the truck (maybe a spring scale to the tiedows in the bed) and measure the deflection with a jig. Move the jacktands 10" narrower and repeat. I'll bet you get the same reading, as it's the suspension that is deflecting despite the narrower width of the jacketsands.

4 side walls make a huge difference in deflection, as does the increased spring rate with a good load applied.

We did not put downward force on the trucks it was side to side force. I agree downward force could not be done by hand. I have 1840 lbs of pin weight and it drops my truck 1.5 inch's. Fact is though push side ways on the bed of a SRW and a DRW and you will see a difference.