Lifting the P38 Air Suspension


Introduction
Front Lift Details
Rear Lift Details
Results
 

Introduction

Many people assume the air spring models cannot be lifted in the conventional sense. Of course this is not true. Although I have not done it, the suspension could readily be lifted by placing spacers under the air springs. In order to keep the travel of the air springs the same as before and avoid damaging them, I would lower the bump stops and shock mounts accordingly, and bend or remount the height sensors to give the same readings at the new height.

 

Andrew Parker lifted his Range Rover 4.0/4.6 by 3.5 inches using these principles (see photo above, taken at "normal" ride height) and shares his procedure with us below. His conversion retains the air springs and all workings with-in.  He reports that the only expensive part was a double cardon jointed and lengthened front drive shaft from Great Basin Rovers.

 

Front Lift Details:

Andrew put rear air spring bladders on the front and used the rear aluminum lower lobes as well which has increased the wheel travel by several inches up front. Andrew also turned the front aluminum pistons flush with the four inch diameter tubing which allows the front bladders to roll further, increasing the effective wheel travel by two or three inches over the OEM setup. He used 9.5 in stroke Edelbrock performer IAS shocks.
 

Front Air spring replaced by rear unit

Lowered front radius arm mount

A truly professional lift preserves the caster angles, so Andrew lowered the mountings for the radius arms accordingly. When he welded the housings for the radius arm bushings to locate in, he set them forward on the frame ahead of the plane the in frame OEM positions are set at.  This moves the axel forward and increases the wheel base by an inch.  It also allows for more tire clearance in side the wheel arch as the wheel and tires outer corner tend to sweep through there under full lock.  This was done in anticipation of the 255/85R16's he plans to run when the 4.10:1 Ring & Pinion gears become available from Great Basin Rovers.

 

As for the front ride height sensors, the front mounts on the frame are unchanged as is the position on the radius arm.  However, the effective change is that the center point of the sensors arch in which it sweeps through is set back one inch closer in relation to the radius arms effective pivot point.  This produces a slightly larger displacement between the height settings as the EAS goes through its leveling routine on the front suspension. The steel link rod which is vulcanized to the rubber bushing ends was cut in half.  The link rods are effectively lengthened by using roughly 6" to 7" long sections of fiberglass tubing to allow the sensor to connect to the radius arm.  The link rods end and tube are bonded with JB weld epoxy and painted gray in the photograph. The result in these modifications has allowed setting the front about an inch higher for all settings.  This has greatly improved the manner in which the Range Rover deals with bumps and holes in the terrain when at some speed.
 

Front shock and lengthened height sensor arm

Modified front Panhard Rod and Steering Link

To lengthen the sway bar link rods, Andrew made extensions of steel tubing that had to be drilled out with a 5/16 diameter drill to get the rods to fit inside the tubes.  Once they were pushed together he ground through the tubes wall thickness into the rod inside and replaced the ground-away material with a weld.  Andrew found two such features were needed to keep these links together, as this years time at the CORVA event made short work of tearing the initial links apart in tension!  This initial problem was due in part to not wanting to melt the plastic covers which seal the swivel caged studs on the link rod ends.

 

Rear Lift Details:

The rear air spring's lower aluminum piston is raised from the axle by some 3.5 inches, by welding on a pair of steel 4" diameter pieces of tubing with steel headers in the ends to fix the pistons to them. Andrew offset the location of the tubes on the axle to help in reducing the bladder's desire to rub on itself as one cycles the axle through its arcs (dictated by the panhard rod and radius arms)
 

Modified rear suspension showing spring with raised piston and limit strap 

Rear suspension showing lifted air spring and lowered  height sensor mounting 

Additionally, the pivot points for the radius arms are lowered under the frame so the geometry for the fully bottomed out condition puts the aluminum piston almost parallel and within ½ an inch of the air springs top plastic cap.  By offsetting the bottom-out stops on the frame and axle Andrew was able to push the collapsed length of the air spring a little further than the stock OEM arrangement allows for.

 

It was necessary to limit strap the travel before the new 9.5 inch travel Edelbrock Performer IAS shocks top out, as the Panhard rod's short relative length shifts the air spring out of alignment from side to side enough to unseat the bladder from the aluminum piston if allowed full droop.  Replacing the rear Panhard rod with a Watts Linkage sould keep the air springs straight and allow at least another inch or two of droop before unseating the rear air spring bladders.
 

Lowered rear radius arm mount

View of complete lifted rear
Photo taken at normal ride height

Meanwhile, the rear Edelbrock IAS shocks are not being fully cycled, as the laid down orientation could produce well over 10 inches of actual wheel travel with these shocks.  Since Edelbrock does not specify any shocks for our Mk II RR's, Andrew used the ones specified for the rear on a late 90's Jeep Grand Cherokee with a 3" lift kit installed.  Both ends are loops with 12mm and ½ inch steel sleeved urethane bushings. This required replacing the shock mounts on the axle with some mounts from Performance Products at this link.

 

The rear ride height sensor housings are lowered 3.25 inches using aluminum plate to offset the mounting holes.  They have ample sweep to accommodate the increased travel.  Andrew does feel he needs another .75 inches of extension, and has these parts modeled in CAD for anyone who would like to make a set.

 

Results

Andrew reports the system is working fine, although he managed to bash his RR up a bit during the CORVA event in January 2003.  "I guess my over exuberance in trying out the new suspension modifications got the better of me"!!  Along with the Edelbrock IAS shocks the ride is most excellent both on and off the road although perhaps just a tad plush in the really rough stuff.

 

The best thing Andrew finds is that that with her lifted like this he can leave the EAS in normal mode and have a very comfortable ride when off roading as the body work and undercarriage are up enough to clear most things.  But the icing is that the air springs are extended a little more than half way which affords excellent
articulation through out the increased wheel travel distance.  Part of this is because the bulge in the top of the aluminum piston isn't completely exposed yet, unlike when the EAS high mode is selected, which allows the the net piston area to be decreased some as the bladder roles down under the bulge during compression over bumps.

 

This feature on the air spring is a big part of the reason why second generation RR's corner so well when they are in Low mode.  By not having the air spring in high mode the suspensions compliance over bumps is much less harsh and the suspension can really work very effectively.  Andrew's neighbor who is an avid desert fan was attending the CORVA event as a spectator this year and caught sight of him on several occasions blazing up the wash to Dos Palms where SCLR was gathering for this event.  His observations were all about how he couldn't get over how stable the body of the Range Rover was as Andrew hit the wash at speeds of around 60 MPH.  The very same wash the previous year was a 30 MPH affair as the front end would pound harshly on the irregularities and tell you breakage was in the works if you kept this up.


 

 

 

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Page revised February 1, 2012