checking tongue weight with Sherline Scale
I am planning to check tongue weight on a few trailers at the dealer. If I use a Sherline scale and measure at the tongue jack, about what percentage will it be off from actual tongue weight at the h...
Forum Discussion
I position the Sherline scale directly underneath the trailer's ball coupler.
In otherwords, the Sherline substitutes for the trailer ball itself.
The trailer ball is where the dead tongue weight is transferred to the towing vehicle (before any weight distribution system is engaged), so it makes the most sense to me to measure at the exact same place.
Measuring directly underneath the ball coupler also provides a more fair comparison from trailer to trailer, regardless of tongue material design or obstructions. No matter how the end of the tongue is shaped, and no matter what kind of hardware appurtenant obstructions exist under the trailer tongue, the ball coupler still has to be able to latch onto a ball with no obstructions.
Why not measure at the ball coupler, and use the tongue jack to raise and lower the ball coupler on and off the Sherline scale in the same manner as raising it off of the ball mount?
The tilt of the trailer effects the measurement of the tongue weight, so having the tongue jack available to adjust the tilt attitude of the trailer to the towing trim is a benefit. I can't imagine anyone trying to place the Sherline scale underneath the foot of the trailer tongue jack... that seems very unsafe.
I would measure the top of ball height on my tow vehicle first, and then recreate that height at home with the Sherline scale. You might be able to find a 6x6 cutoff blocks, or a stack of plastic RV leveler blocks, or a concrete pier block, or a jack stand... an endless number of objects can be placed under the Sherline to ultimately simulate ball mount height.
That ball height will lower once the weight of the trailer is mounted on the ball, but with weight distribution, some of that lowering will be recovered. If the trailer is light enough where no weight distribution is required, then I would consult the tow vehicle manufacturer's specifications for rear spring deflection. For example, the rear springs might deflect 1 inch per 600 lbs of weight added in the first stage, before overloads kick in. Then the second stage might be 1,400 lbs per inch. Whatever they may be, an accounting could be made for this deflection by reducing the height of the Sherline scale by an inch or two accordingly, to best simulate the actual trailer tilt attitude when finally hitched up, which will make for more accurate tongue weight measurements, in my experience.
In otherwords, the Sherline substitutes for the trailer ball itself.
The trailer ball is where the dead tongue weight is transferred to the towing vehicle (before any weight distribution system is engaged), so it makes the most sense to me to measure at the exact same place.
Measuring directly underneath the ball coupler also provides a more fair comparison from trailer to trailer, regardless of tongue material design or obstructions. No matter how the end of the tongue is shaped, and no matter what kind of hardware appurtenant obstructions exist under the trailer tongue, the ball coupler still has to be able to latch onto a ball with no obstructions.
Why not measure at the ball coupler, and use the tongue jack to raise and lower the ball coupler on and off the Sherline scale in the same manner as raising it off of the ball mount?
The tilt of the trailer effects the measurement of the tongue weight, so having the tongue jack available to adjust the tilt attitude of the trailer to the towing trim is a benefit. I can't imagine anyone trying to place the Sherline scale underneath the foot of the trailer tongue jack... that seems very unsafe.
I would measure the top of ball height on my tow vehicle first, and then recreate that height at home with the Sherline scale. You might be able to find a 6x6 cutoff blocks, or a stack of plastic RV leveler blocks, or a concrete pier block, or a jack stand... an endless number of objects can be placed under the Sherline to ultimately simulate ball mount height.
That ball height will lower once the weight of the trailer is mounted on the ball, but with weight distribution, some of that lowering will be recovered. If the trailer is light enough where no weight distribution is required, then I would consult the tow vehicle manufacturer's specifications for rear spring deflection. For example, the rear springs might deflect 1 inch per 600 lbs of weight added in the first stage, before overloads kick in. Then the second stage might be 1,400 lbs per inch. Whatever they may be, an accounting could be made for this deflection by reducing the height of the Sherline scale by an inch or two accordingly, to best simulate the actual trailer tilt attitude when finally hitched up, which will make for more accurate tongue weight measurements, in my experience.
