How to Calculate Permissible Mass

Calculating permissible tractor mass and permissible trailer mass on the basis of the D value

EC-approved, dynamically tested trailer hitches are always provided with a D value. This is calculated as follows:

D =	G * A * B A + B	, where
D =	D value of hitch
G =	Gravitational constant 9.81 m/s2
A =	Tractor mass
B =	Trailer mass

To calculate trailer mass for a given D value and a given tractor mass, and to calculate tractor mass for a given D value and a given trailer mass, use the following formulas:

Tractor mass	A =	D * B G * B - D
Trailer mass	B =	D * A G * A - D

NOTE: If when calculating A the product of G*B is less than the D value, or if when calculating B the product of G*A is less than the D value, then the result of this calculation is negative. Even so, the D value is sufficient for every combination of tractor mass and trailer mass.

Example of how to calculate permissible trailer mass:

Given that:	D value, D = 55 kN = 55000 N
	Tractor mass A = 7000 kg
B =	55000 N * 7000 kg 9.81 m/s2 * 7000 kg - 55000 N	= 28163 kg

Pay close attention to permissible towed mass and tractor mass!