Air Suspension Height Control Valves ("Leveling Valves")
Can the height of your air suspension be adjusted to be more comfortable or convenient?
According to Hendrickson Truck there is only one correct ride height setting. Changing the height invites more maintenance problems including driveshaft vibration because of incorrect driveline angles and premature failing of shock absorbers.
Although height control valves allow for adjustments, the adjustments were expected by the manufacturer to be nothing more than is required by the slight lack of precision that is tolerated in the manufacturing of a large number of suspension parts that must be fitted in final assembly. As a rule, ride height should never be manually adjusted once the vehicle leaves the assembly line. However, the settings should be checked and adjusted again after any repair is made to suspension components, especially those that require disassembly of the system.The linked article at the right provides additional information specific to Hendrickson truck air suspensions.
Ridewell's Universal Levelling Valve
Helpful Info about Tractor/Trailer Ride Height Control
Integrated dump valve; fits Navistar/International Air Suspension
Multiple brackets & control levers for retrofit all installations
Hadley 500 series pn H00500C; tight dead band
334-1647
Replacement for Hendrickson pn VS-227
334-1648
Replacement for Hendrickson HAS suspension
Integrated dump valve; No-delay for EDGE system
334-1836
Ridewell "Extreme Air" height control valve
Includes valve, bracket, linkage, hardware oe pn 6300BFAB00
Mfg by Ridewell for all Ridewell suspensions plus many others
334-750
Universal height valve for tractor/trailer
Includes multiple brackets; fits many different suspensions
No dump valve; Hadley 450 series pn H00450CA
Haldex
90054007
Controlled response CR valve for trucks/trailers
Dump valve not included; all ports 1/8" NPT
Does not respond to short duration height changes
90555100
Replacement for Holland Neway trailer suspension
No-delay response PR Plus model w. ceramic seal
Integrated normally closed dump valve; push to connect fittings
pilot port 1/4"; other ports 3/8"; 5" adjustable arm
90555263
No-delay PR Plus replaces Volvo 90555356
PR Plus model w. ceramic seal; 7" fixed length arm
3 port side manifold; pilot port 1/4"; other ports 3/8"
Integrated normally open dump valve; push to connect fittings
90555318
PR Plus replaces Volvo 90555357, 90555289
PR plus w. ceramic seal; 7" fixed length arm
Integrated normally open dump valve; push to connect fittings
3 port side manifold; pilot port 1/4"; other ports 3/8"
90555353
No-delay PR Plus replaces Volvo 90555355
Integrated normally open dump valve; push to connect fittings
5 port side manifold; pilot port 1/4"; other ports 3/8"
PR plus model w. ceramic seal; 7" fixed length arm
90555375
No-delay PR Plus replaces Kenworth 90555141
Integrated normally open dump valve; push to connect fittings
3 port side manifold; pilot port 1/4"; other ports 3/8"
PR Plus model w. ceramic seal; 7" fixed length arm;
KN27000
No-delay standard-flow for truck/trailer
Engineering Grade Plastic; dump valve not included
adjustable arms, 12" max horizontal, 14" mac vertical; ports 1/4"
KN27010
No-delay standard-flow for Navistar
Engineering Grade Plastic; dump valve not included
adjustable hoizontal arm 8.2" max; no vertical arm
Hendrickson
AKEM0005-1
VS-27116
Differential height control valve with dump
Meritor
S4640024430
Chassis leveling valve, non-ceramic
S4640070040
Cab leveling valve for IH, Peterbilt
About Haldex valves with included dump control feature
Haldex dump controls are designed to be operated from the cab, from a gladhand, or to automatically function when the emergency brake is set.The “normally open dump valve” needs air pressure to dump and is activated by a manual switch or electric solenoid. The “normally closed dump valve” will dump if air pressure is removed and is typically operated by a gladhand or emergency brake line. Plaza's most popular leveling valve, the Haldex 90054007, which is often found as original equipment, does not include a dump valve.
Haldex 90054007 - Plaza's most popular height leveling valve for truck or trailer
Air Suspensions Using Dayton Parts 334-750 Universal Height Control Valve
Dayton Parts recommends that all of the following suspensions are able to use their part 334-750 which was designed for general applicability and is pictured at the bottom of this page. However, Haldex makes a similar claim for both of its models, "PR" and "CR". In order to determine if a valve is truly interchangeable it is probably a good idea to verify that the port sizes are identical and that the brackets allow the valve to be mounted in the same position. At Plaza we do this every day.
Hendrickson Trailer - INTRAAX AAL and AAT/AANT/AAEDT
Hendrickson Trailer - VANTRAAX HKA/HKANT/HKAT
Hendrickson Trailer - T-4/6/9/15/17
Hutch - H1200 (Mk2/LMk2/E/F) Trailer Air & Air Lift Suspensions
Kenworth - 'Airglide' 100
Navistar/International Air Suspension 'Z' Beam
Neway - AR120/125, AR120US/125US
Neway - AR41/45/75/85
Neway - AR50-US/USF/USF1/USF2
Neway - AR70/80/95/955
Neway - AR90/90-1/92/93/250, ARU92/93
Neway - ARD120/238, 125/244, 234
Neway - ARDST123/244, 246, 250, ARDSTM/L 123/246
Neway - ART500/505/541/550/551/555 - Non-Powered Tractor Air Suspensions
Neway - RL196/196A/228
Peterbilt - Air Leaf and Air Trac®
Reyco - 23/25/30AR, 74AR, 86AR Single/Tandem Axle Trailer Air Suspension
Volvo - Corporate 'Air Ride'
Background info: How does Height Control Work ?
A height control valve is typically mounted to the frame.“Ride height” is specified by the chassis manufacturer with measurements defining the distance between the frame and the axle. The average lift that an air bag will supply when inflated to the maximum is between 5 ½ and 6 ½ inches from a totally deflated state.
One of the benefits of an air suspension is that it will always operate at the proper (optimal) ride height. The ride height for other suspensions will change when weight is added or removed. Leaf springs will also “settle” as they age.
Since air is compressible, the frame would normally move up and down as weight is added or removed. Also when a vehicle leans, the suspension transfers weight from one side to the other. There are two approaches to height control with an air suspension.One approach is “instant response” which adds or removes air pressure to an air spring as soon as a height difference is measured. This change in pressure then restores the frame to the optimal ride height. The other approach to height control operates with a slight delay between the change in measured height and the application of air pressure to the air spring. The delayed approach will work to conserve system air pressure because it is possible that a movement of the frame is only temporary and the optimal ride height will be restored without intervention.
