Looking for an answer

[AdamKam]

Recently in a discussion on tongue weight or drive axle weight I stated that my rear wheel weight decreased by 400 lbs with 24 gallons less fuel which is about 150 lbs. Would this indicate that some sort of leverage factor is involved, where the trailer wheels being a pivot point may amplify the weight change. Maybe out there is someone with rocket science knowledge that has an answer.

[SeaDog]

I would think as the rear of the truck would rise with the removal of fuel thus lifting the tongue of the trailer may account for the weight transfer. This is just a wild guess on my part.

[clarkbre]

A couple things to keep in mind:

• For every action, there's a reaction.
• The rear axle of the tow vehicle and the trailer's axle(s) are fulcrum points.

With the above said, any weight added to an area of a trailer or tow vehicle will have an opposite effect to the other side of that axle.

Examples:

1. Hitching your trailer to the tow vehicle. The tongue weight of the trailer puts downward force behind the rear axle (fulcrum point). In turn, the front of the tow vehicle slightly raises up.
   
2. Changing the tongue weight of the trailer can easily happen from the rear of the trailer. In this case, the trailer's axle(s) act as the fulcrum point. By adding or removing weight at the rear of the trailer, the tongue will see the opposite.

My personal example of this was increasing tongue weight by removing the factory mounted bike rack on the bumper of the trailer. The rack weighed 82 pounds and was 129" from the trailers axles (fulcrum). By removing the 82 pounds off the bumper, this put more downward force on the tongue. With the coupler being 225" from the axles, this resulted in 47 more pounds of tongue weight.

Think of it as 2 kids weighing different amounts on a teeter-totter. Two equal weight kids can be equal distance from the fulcrum point and balance. two kids with different weights have to be different distances from the fulcrum point.