Hendrickson Trailer Parts Catalog

ZMD ® Frequently Asked Questions


1. What is ZMD ® ZERO MAINTENANCE DAMPING ® technology? ZMD ZERO MAINTENANCE DAMPING technology consists of a patented ▲ air spring and a down stop that are designed to replace the function of a standard shock absorber to help lower maintenance, improve ride quality and enhance cargo protection. 2. What are the benefits of ZERO MAINTENANCE DAMPING technology? ZMD offers improved ride quality and helps lower maintenance over the trailer’s life cycle due to the elimination of the shock absorbers. It provides better cargo protection and reduces the risks associated with possible CSA violations of applicable U.S. Federal Motor Carrier Safety Administration regulations.

3. What are the advantages of ZMD air springs compared to shocks over the lifetime of the trailer? Shocks are a common maintenance item on air suspensions that must be replaced periodically. Over time, as shocks wear, their damping capabilities also diminish. ZMD air springs are designed to provide continuous and consistent damping levels throughout the life of the air springs. Since there are no shocks to wear out, the ZMD option helps save time and labor costs over a trailer’s life cycle. 4. What are the key design features of ZMD air springs? The main components of a ZMD air spring are similar to those of a standard air spring - both have a rubber bellow and a steel or plastic piston. The internal design components of this patented air spring are specifically designed to perform the suspension damping function traditionally performed by the shock. 5. How does a ZMD air spring work? The ZMD air spring exchanges pressurized air between the bellows and piston through channels that interconnect to provide continuous suspension damping. 6. Traditionally, shock absorbers are responsible for controlling the travel of a suspension to prevent overextending the air springs. Since ZMD eliminates the shocks, how will the travel be controlled? The ZERO MAINTENANCE DAMPING design features down stops to limit suspension travel. The down stops are installed where the shocks would traditionally be. 7. Is ZMD available on all suspension systems? NO. Currently ZMD is standard on ULTRAA-K ® air slider systems. It is an option on select VANTRAAX ® and INTRAAX ® models. Only VANTRAAX HKANT 40K with a 16-inch ride height equipped with Hendrickson’s QUIK-DRAW ® fully pneumatic pin-pull system are available with ZMD. INTRAAX AANT 23K and AAT 23K / 25K models with a 14-inch through 17-inch ride height and standard travel are available with ZMD. INTRAAX AAT 23K / 25K RCA models with a 14-inch or 16-inch ride height and limited rebound travel are available with ZMD. 8. Is ZMD the only option available when specifying a new VANTRAAX or INTRAAX suspension? On select VANTRAAX HKANT 40K models and select INTRAAX AANT 23K and AAT 23K / 25K models, ZMD is an option that is available to customers who wish to upgrade their suspension. Customers still have the option of specifying a suspension with standard air springs and shocks on the HKANT 40K, AANT 23K and AAT 23K / 25Kmodels. (Please refer to Hendrickson Literature Numbers L602 INTRAAX Ordering Guide, L544 VANTRAAX Ordering Guide and L1226 ULTRAA-K Ordering Guide for a complete list of options) 9. Can ZMD be retrofitted on existing trailers in service? YES. ZMD air springs and down stops can be retrofitted on select VANTRAAX and INTRAAX models with the following specifications. VANTRAAX HKANT 40K models require a 16-inch ride height and QUIK-DRAW ® . ZMD is compatible with Hendrickson’s SURELOK ® device. INTRAAX AANT 23K and AAT 23K / 25K models are available with 14-inch through 17-inch ride heights and standard travel. INTRAAX AAT 23K / 25K RCA models are available with 14- or 16-inch ride heights and limited rebound travel. Please call Hendrickson for assistance in ordering a ZMD retrofit kit.


Trailer Commercial Vehicle Systems

Refer to Hendrickson Literature No. L1212 - ZMD ® Zero Maintenance Damping ® FAQ Brochure

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