In this write up, it says to measure from the lower flange on the frame rail to the center of the lower shock bolt. This is from Freightliner's manual.
5. Check the ride height of the air suspension by
measuring the distance from the center of the
lower shock bolt to the bottom of the frame rail.
See Fig. 1. See Table 2 for height control valve
adjustment measurements. If ride height is incorrect,
adjust the air suspension.
Height Control Valve Adjustment Measurements
Inches ±1/4 (mm ±6)
AS120 (front) 10 (254) or
AS140 (front) 11 (279)
IFS114 (front) 17-1/2 (445)
IFS ZF (front) 15-3/4 (400)
ADL-RS17/19/21 10-1/4 (260)
AD200-RS17/19 9-3/4 (248)
AD200-RS15 9-3/8 (238)
ADTB280 (rear) 17-1/4 (438)
Airliner 15k (rear) 8-3/4 (222)
AD123 (rear) 18 (457)
ADL123 (rear) 11 (279)
* Some vehicles have a different shock location. When this is the case, the
vehicle will have a 55 degree wheel cut. Ride height for these vehicles
should be set at 10-1/2 inches (267 mm).
Tom and Margaret
2014 Berkshire 390bh-60