Technical
PROCEDURE

TRAILER SUSPENSION SYSTEMS


SUBJECT: Recommended Ride Height Settings

LIT NO: L388 
DATE: September 2017
REVISION: H
The tables in this publication list the recommended
or “designed” ride heights for all current Hendrickson
trailer suspensions. The designed ride height helps
optimize suspension performance and helps maintain
load equalization among the axles.

For safety and precautionary statements, refer to
Hendrickson literature number T12007, available at
www.Hendrickson-intl.com/TrailerLit.
I. USING A HENDRICKSON RIDE HEIGHT GAUGE

NOTE: Ride height is just one of many factors that
influence load equalization. Even small
adjustments in ride height (within the specified
range) can impact the way the load is
distributed among the axles.
Operating an air suspension outside its specified ride
height range can reduce ride quality, damage cargo
and increase suspension wear. To take full advantage
of the benefits an air-ride suspension has to offer, each
suspension on the trailer should be operated at its
designed ride height.
A-23445
Suspension mounting surface
(bottom of trailer or slider box)

A-23442

Figure 2: Hendrickson ride height gauges

Follow instructions on the gauge (Figure 2) to measure
the distance between the axle and the mounting
surface of the suspension. A ride height gauge works
with both 5-inch and large diameter axles (LDA™). Just
make sure you are using the proper scale on the ride
height gauge. The tool can also be used as a GO/NOGO gauge.

Ride
Height

Axle
center
Figure 1: Ride height defined

A suspension’s designed ride height is defined as the
distance from the suspension mounting surface (the
bottom of the trailer frame or slider box) to the center of
the axle. See Figure 1.
There are two easy ways to determine a suspension’s
ride height:

NOTE: To order a Ride Height Gauge, contact the
Hendrickson customer service department at
866.RIDEAIR (743.3247) and specify:
A-23442 Ride Height Gauge for conventional topmount suspensions
A-23445 Ride Height Gauge for low-ride
suspensions.

II. USING A TAPE MEASURE
1. Measure the distance from the top of the axle to
the mounting surface of the suspension (Figure 3).

Recommended Ride Height Settings 
2. Add half of the axle diameter to this measurement
to determine your suspension’s ride height.

height set below the specified minimum ride height
value will prevent the SURELOK support arms from
properly engaging. See Figure 5.

For example: on 5-inch axles, add 2½ (2.5) inches
to the measured distance, and on LDA™ Large
Diameter Axle, add 27/8 (2.88) inches to the
measured distance.
3. Compare this measured ride height with the listing
in the appropriate table (see page 4 through
page 7).
NOTE: While we recommend that our suspensions
operate at their designed ride height, they
can be satisfactorily operated within the
range listed in the table applicable to your
suspension model or type.
If the measured ride height does not fall within the
range listed in the table, the suspension’s ride height
must be adjusted. Refer to Hendrickson publication
L459 Checking Trailer Ride Height, for complete ride
height adjustment instructions.

Figure 3: Measuring ride height using tape measure

If your suspension model number is not listed in the
tables, contact the Hendrickson technical service
department in the United States and Canada at
866.RIDEAIR (743.3247) for ride height range
information.

DESIGNED RIDE HEIGHT AND SURELOK®

SURELOK® is a ride height locking device that uses
mechanical support arms to maintain the trailer’s
height for efficient trailer loading. When engaged, the
mechanical support arms help limit trailer “drop” and
“walk” during the loading/unloading process.

Figure 4: Ride height set too high

A. If ride height is set above specified maximum value
(Figure 4), The trailer has the potential to exhibit
excessive “walk” and/or drop before the SURELOK
support arms can contact the beam and maintain
trailer height.

NOTE: Refer to Hendrickson publications L816,
DOCK SOLUTIONS or T15001, TRAILER AIR
SUSPENSIONS CONCEPT AND FUNCTIONS for a
complete description of trailer drop and walk.
If a suspension is equipped with SURELOK, it should
be operated as close as possible to its designed
ride height. Suspension ride height is the primary
consideration for optimal SURELOK performance
(not the amount of clearance between the SURELOK
support arms and the suspension beam). When the
suspension is operated at its designed ride height, the
SURELOK support arms will have the proper clearance
from the suspension beams.

Figure 5: Ride height set too low

B. If ride height is set below specified minimum value
(Figure 5), The SURELOK support arms (shown in
retracted position) cannot contact properly engage
the beam.

Any increase above the specified maximum ride height
can reduce the effectiveness of SURELOK to limit trailer
drop and/or walk. See Figure 4. Conversely, any ride
2

L388 H

Recommended Ride Height Settings
INTRAAX® AAT 23K, AAT 25K & AAT 30K LARGE DIAMETER AXLE RIDE HEIGHT SETTINGS*
SUSPENSION
TYPE

STANDARD

HIGH CONTROL

LIMITED REBOUND

LIMITED JOUNCE

DESIGNED
RIDE HEIGHT

MINIMUM
RIDE HEIGHT

MAXIMUM
RIDE HEIGHT

13.5"

13.25"

15.75"

14"

13.25"

15.75"

15"

14.25"

15.75"

16"

15.25"

17.75"

17"

16.25"

17.75"

18"

17.25"

19.75"

19"

18.25"

19.75"

13.5"

13.5"

16"

14"

13.5"

16"

15"

14.5"

16"

16"

15.5"

18.5"

17"

16.5"

18.5"

14"

13.25"

14.5"

16"

15.25"

16.5"

18"

17.25"

18.5"

14"

14"

15.75"

15"

15"

15.75"

16"

16"

17.75"

17"

17"

17.75"

DESIGNED
RIDE HEIGHT

MINIMUM
RIDE HEIGHT

MAXIMUM
RIDE HEIGHT

14"

13.75"

15.25"

INTRAAX® AAEDT 30K RIDE HEIGHT SETTINGS
SUSPENSION
TYPE

STANDARD

15"

14.5"

15.75"

(FRONT SHOCKS)

16"

15.25"

17.75"

17"

15.25"

17.75"

14"

13.75"

14.75"

STANDARD

15"

14.5"

15.5"

(REAR SHOCKS)

16"

15.25"

17.5"

17"

15.25"

17.5"

* If any of these suspensions are equipped with SURELOK®, they should be operated as close as possible to the designed ride height. Refer
to the section titled DESIGNED RIDE HEIGHT AND SURELOK® on page 2 for details on how an improper ride height can reduce the
effectiveness of SURELOK to limit trailer drop and/or walk, or prevent the SURELOK support arms from properly engaging.
L388 H

3

Recommended Ride Height Settings 
INTRAAX® AAL 23K, AAL 25K, AAL 30K, AAEDL 30K AAZL 23K & AAZL 46K RIDE HEIGHT
SETTINGS
SUSPENSION
TYPE

STANDARD

LIMITED JOUNCE

1

DESIGNED
RIDE HEIGHT

MINIMUM
RIDE HEIGHT

MAXIMUM
RIDE HEIGHT

6.5" 1

6.5" 1

7.5" 1

7.5" 1

6.5" 1

7.5" 1

8" 1

7.25" 1

10" 1

9"

7.25"

10"

12"

10"

13.5"

14"

11.25"

15"

15"

12.75"

15"

16"

13.5"

17"

17"

14.25"

17"

19"

16.5"

19"

21"

18.5"

21"

9"

8.5"

10"

12"

11"

13.5"

14"

12.5"

15"

15"

13.5"

15"

16"

14.5"

17"

17"

15.5"

17"

19"

17.5"

19"

21"

19.25"

21"

Ride height not available on AANT 23K models.

INTRAAX® AANT 23K, AAZNT 23K, AAZNT 46K & AAZNT 69K RIDE HEIGHT SETTINGS*
SUSPENSION
TYPE

STANDARD

ZMD STANDARD

1

DESIGNED
RIDE HEIGHT

MINIMUM
RIDE HEIGHT

MAXIMUM
RIDE HEIGHT

12"

11.75"

13"

13.5"

13.25"