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Hi Jim, The rule of thumb is 66% of total trailer length to center line of axle(s). Example; If you had a 20ft tandum axle trailer then from the center of the pin to the center line of alxes would be 13ft 2.5". Remember since you have tandum axles then axle center line would be 1/2 the distance between the axles. This works well for most vechiles as well for most dead load weight. On bumper pull trailers you want to keep 12% to 15% tongue weight or you'll induce trailer sway. However your talking rolling load weight with hauling tractors and it would be very easy to get too light of tongue weight depending on the load weight placement, on a typical trailer axle placement of 66%. The futher back the alxes are placed from the pin the more forgiving of rolling load deck placement in requards to trailer sway. The trailer will pull alot better. This creates another problem of having too much tongue weight (TW) for some tow vechiles, your apparent problem. If you would scale the TW on your existing alxe placement you might be surprised that you may not have to move the axles depending on where you place the load on the deck. You can use a bathroom scale to check TW. You need a horizontial 4x4 x 36" or longer. This will support the tongue weight. More tongue weight= a heavier support Set one end of the 4x4 on a block( thick as the scale height) 1ft from the center of tongue pin/ball/coupler. Set the "center" of scale 2ft from the center of tongue the other end of the 4x4. Apply Tongue weight to the 4x4. Read weight on scale.
Multiply the scale reading by 3 and this is your tongue weight. Scale reads off the scale dial? Increase the 2ft distance to 3ft then multiply by 4 and this would be your tongue weight. You have to multiply by the total horizontal center distance in feet between the scale and the ground support block. The 1ft dimension never changes. Only the dimension from the center of scale to the center of hitch pin changes. This can be any length for any given tongue weight but remember to always multiply the total feet between ground support and center line of the scale For this method to be accurate, your measurements must be exactly "centers" of 1ft and 2ft for a 3ft total spread between supports. Do not forget to block the trailer wheels. A class III receiver = 5000lbs max GVW
Class IV = 10000lbs max GVW
Class V = 14500lbs max GVW From what I've seen of the mfg receivers, do not abuse the maximum GVWR. T_Bone
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