How to Scale a Tandem Axle Trailer
Scaling a tandem axle trailer. The 'how-to' of balancing the axle
weights on a tandem trailer and big rig truck, is pretty straight
However, scaling is one of those things that many truckers have
difficulty with, usually because they've never been taught the process.
driver training schools and programs don't seem to spend enough time on
this important skill, so it's pretty common for a trucker to have
difficulty balancing the weight of their load.
Scaling isn't a difficult or complicated process. However, it does take some practice to get the hang of it.
Here's a simple step by step outline of the process of scaling a big rig truck with a tight (closed) tandem axle trailer.
For 80,000 lb gross weight, the goal is 12,000 lb on the steering axle,
34,000 lb on the drives and 34,000 lb on the trailer axles
- Before beginning, lock the trailer brakes.
- Load the steering axle first.
- Lower the landing gear, unlock the fifth wheel, dump the tractor airbags. Cautiously back up the truck toward
the trailer until the tractor is as close to it as it can safely be
without affecting the truck's ability to turn. Be sure to get out of
the vehicle and visually check the distance. When you've determined the
distance is safe and correct, lock the 5th wheel in place, inflate the
tractor air bags and raise the landing gear.
- Release the slider pins.
the trailer brakes still locked, release the slider pins underneath
the trailer and slowly back up with it's wheels locked so the axles are
sliding further underneath the trailer. Sliding the trailer wheels
further under, decreases the drive axle wt. and increases weight on the tandem axles. Generally
the rule of thumb, is about 400 lb. per hole on the trailer slider.
- Scale the truck and adjust accordingly.
If the weight on the trailer axles is too heavy, these wheels need to
slide backwards to the rear of the unit until they reach 34,000 lb. on
Important things to remember When scaling a tandem axle trailer
- Do not slide and adjust on the scale plate. Pull away and make adjustments and then rescale.
- When scaling, we like to load the steering axle and tandem trailer axles to maximum when possible, leaving some room for extra wt. on the drives, to allow for the weight of taking on fuel.
- The weight of fuel is calculated at about 7 lb/gallon...it's a nice easy number to do the math in your head. This formula will help you calculate how much weight to load on the drives, before you fuel.
- In the winter months, it is advisable to leave a bit more weight on the drives to help with traction when climbing hills and to prevent spinning out.
- Always do adjustments on flat, dry pavement, to prevent locked axles from sliding and to ensure slider pins reset correctly, after locking.
- The process varies according to the number of axles, as the various states and provinces dictate their axle wt. allowances.
Smart Trucking Tip
For truckers who own their trailers,..... if your budget allows for it, consider a spread tandem axle trailer.
Scaling a spread axle trailer with a 10'1" spread or greater, is much easier to scale than a tight tandem axle unit. Allowance for these wagons is 20,000 lb per axle. They are quite slick!
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