Parts and Service >> Folding Air Springs on HT25OUS


The standard air spring for Hendrickson's HT25OUS suspension series provides a lower suspension operating pressure. However, this air spring may also be more susceptible to folding over during some operating situations. When the air spring's rubber flex member folds towards the tire, the flex member can be damaged.

The air spring is most likely to fold when a trailer is lifted and the suspensions are allowed to drop away from the trailer frame, as in when a trailer is placed on top of other trailers or on railroad flat cars. When a trailer is unloaded from these situations, the air springs whould be checked for folding before it is operated.

If a folded air spring is observed, the air spring should be straightened as follows: Release the trailer parking brakes to allow the suspension to raise or lower the trailer. Connect air to the trailer until the suspension has raised the trailer to the proper ride height. If the fold is eliminated, no further action is required. If the air spring is still folded, proceed to Step #3. Disconnect the link from the height control valve, rotate the valve arm up and slowly raise the trailer until the fold has been eliminated (See Figure #1 and #2). You will typically hear a popping noise as the air spring flex member seats itself. Rotate the height control valve arm down to lower the trailer to the proper ride height (See Figure #3) and observe the air springs. If the fold is eliminated, reconnect the height control valve link and proceed with the normal operation of the trailer. If the air spring is still folded, return to Step #3.

CAUTION: Stay clear of all moving components when raising or lowering the trailer.