Remember to consider the weight of diesel fuel when scaling a truck! More than once, I've noticed a new driver scale his rig after loading, finding his gross weight is under the legal gross allowable, then happily head off down the road. He then loads up on product, only to be be ticketed for being overweight at the next scale.
Far too often, new truckers will forget to calculate in the weight of the fuel and on which axle group the fuel weight will alter the overall weight.
This of course, is different for each big rig truck and changes with each load.
However, in general a driver needs to be familiar with his equipment and his axle wt. when loading or fueling.
Just a simple calculation of diesel fuel weight and some trip planning, can make a trucker's day go so much more smoothly!
In the U.S., it's easy on a five axle set-up. 80,000 lbs. gross wt. is allowed, with a maximum of 12,000 lbs on the steering axle and 34,000 lbs on the drives and trailer axles.
10' or greater spread axles are allowed a total of 20,000 lbs on the spread, but still held to a maximum of 80,000 lb gross.
But most new drivers don't pull spread axles, so let's stick to the 12,000, 34,000, and 34,000 lb. set up.
When fueling, depending on where on the tractor's tanks are located, the diesel weight will primarily ride on either the steering axle or the drives.
Most drop nose rigs carry their tanks far forward on the frame, underneath the cab doors while most long hood conventional trucks, carry their tanks, underneath the bunk.
Obviously then, when a long hood truck is fueling, with his tanks underneath the bunk, most of the weight of the fuel being added is going to end up on the drive axles.
For this reason then, a long hood truck needs to maximize the allowable weight, after loading onto the trailer and steering axles, to allow room for added weight to the truck when fueling.
On a 77,000 lb. gross unit, the truck driver wants his steering as close to 12,000 lbs as he can safely get it and his trailer as close to 34,000 lbs. as possible, to allow him a 31,000 drive weight, leaving a 3,000 lb 'buffer', to add fuel without being overweight.
3,000 lbs is more than enough for virtually all highway trucks unless they are capable of carrying more than 300 gallons of diesel, which most trucks are not able.
We like to round off the weight of diesel fuel, just to make it easier. Use the round figure of 7 lb. per gallon, when calculating the weight.... One hundred gallons = 700 lbs.
The weight of diesel does vary somewhat.
Temperature also affects the weight too, but minimally.
If you find you're close to your legal limits on weights, common sense dictates, not to take on fuel just before entering a weigh scale. Know where the scales are located on your route and calculate in fuel stops.
This simple little bit of road trip planning will prevent big tickets on overweight fines and also a lot of major aggravation!