Trailer length vs tow vehicle wheelbase

[Randy W]

I just could not resist jumping in here. I have questioned both TL road tests and the WB formulas seen floating around these boards for quite some time now. Towability is a combination of lengths and weights and countermeasures. Wheelbases are like pivot points and the distances between them are like levers. If you push sideways on the rear corner of the TT, the wheels act like a fulcrum and the torque moment is coupled to the hitch ball, the next pivot point. The force X distance product for each end will be the same so the shorter the distance from the rear corner to the wheels, the less force is applied to the hitch through the longer moment arm. At the hitch, the next fulcrum point would be the rear axle of the tow vehicle, again the distance between the hitch and the rear axle becomes the moment that gets transfered to the front wheels. This is where the wheelbase comes in to play, the longer the wheelbase, the less force is applied to the front wheels. As far as weights go, if the tow vehicle weights more that the trailer the tail can't wag the dog, however if the trailer weighs more than the tow vehicle, the tail can wag the dog. The countermeasures I refer to are the WD hitchs and anti sway devices that work on dampening the motion around the hitch ball.

So when do all of these items come into play - think of a semi passing you in slow motion (he is only going 1mph faster than you) His bow wake hits the rear of the TT pushing it towards the side of the road, that force causes the hitch to move the opposite way and that causes your tow vehicle to want to steer for the ditch. As the bow wake moves forward along the TT the force is placed directly on the hitch and now you feel like you are being sucked toward the truck. When the bow wake hits the side of your truck you want to head for the ditch again. If the tow vehicle is heavy with respect to the TT then the effcts of the bow wake are minimized, however if your tail can wag the dog well .........

So, what is the best combination? That is hard to say, a heavy tow vehicle/light trailer will hide any wheelbase issues better than a light tow vehicle/ heavy trailer. On the other hand, the amount of rear overhang on either the trailer or tow vehicle could be of concern. The only real combination to stay away from is a long heavy TT with a long rear overhang and short light tow vehicle.

Randy
'99 Tahoe
'99 Trail-Lite 7211

[Ariel1935]

Someone almost got to my main question. Does the ratio of TV rear overhang to wheelbase make a substantial difference? I have a 2005 Durango with an overhang of 6" less than the "apparent" pivot point of the Hensley Arrow hitch. I tow 8200 lbs with a rating of 8650 lbs.

Question 2. What can I do to improve the Durango?