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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
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Height Control Valves Currently in Stock
| DaytonParts |
| 334-1580 | Universal height valve for tractor/trailer |
| | 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 |
|
 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.
| Freightliner - FAS Airliner |
| Fruehauf - NT-2/NT-2W Pro-Trac and T1 Cargo Care |
| Granning - L225 - Lift Axle Suspensions |
| Hendrickson Auxiliary - HLM/HLM-1, HLM-2 Lift Axle |
| Hendrickson HA 180/200/230, HA 360/400/460 |
| Hendrickson HAS 120/150/230, HAS 360/400/402/40LH/460 |
| Hendrickson Trailer - HK/HS 190/230, HT 190/230/250/300 |
| 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.
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.
 Dayton pn 334-750 (Hadley H00450CA) |
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 Pn 334-1836 Ridewell's Leveling Valve detail view |
