Suspension Details & Modifications

Flexible suspension demo
Range Rover Suspension Innovation
Coil Suspension Details
Air Suspension Details
Traction Advantage of Soft Suspensions
Articulation and Ramp Travel Index
Suspension Mods for Better Handling
Suspension Mods for Articulation
Suspension Lifts
Air Suspension Diagnosis and Repairs
Other Suspension Mods, Upgrades & Repairs

 

Range Rover Suspension Innovation

Suspension innovation is such a vital part of the Range Rover design and heritage that it deserves special attention. It is probably the most important factor in the vehicle's off road superiority over all competitors.

 In 1970, at a time when almost all 4x4s used primitive leaf springs, the Range Rover pioneered the use of soft, long travel coil springs on all four wheels. This arrangement caused a lot of raised eyebrows among off-road journalists, even as late as 1987 when it was introduced to the US. It took another 5-10 more years before the four wheeling fraternity finally recognized the value of this feature, and owners of specialized trail rigs of all brands began modifying them to provide extreme axle articulation.

By this time Range Rover suspension design had already leaped ahead into the next generation of innovation -- the electronically controlled, self leveling, variable height pneumatic suspension pioneered on the Range Rover County LWB in 1993. The ability to reduce ride height for high speed cruising, increase it for off road clearance, maintain a level ride regardless of load, and maintain articulation were major breakthroughs.  The staggering capabilities of this system, in combination with the simultaneously introduced electronic traction control, took the four wheeling world by surprise, and other manufacturers have made no more than a token attempt  to catch up.

Meanwhile, in case they do, yet another generation of Range Rover suspension innovation has now appeared in the Mark III Range Rover. This all-independent air suspension has even more travel than the solid axle one it replaces. In a major leap forward, the air springs are cross linked (left to right) when off road, reducing the effective spring rate to near zero. This not only softens the ride but increases the ground contact force and traction considerably on a drooping wheel. It also makes the independent setup simulate the articulation motion of a beam axle, getting around the usual criticisms of reduced effective off road clearance on uneven terrain that independent suspensions usually receive. Aside from these advantages, the independent suspension gives much improved ride and steering control over bumpy terrain.

By comparison, some other manufacturers are still emerging from horse-and-buggy technology of leaf springs, especially on the rear of their vehicles.

 

Coil Suspension Details

The main secret to the amazing off road traction of the Classic Range Rover was its use of exceptionally soft springs. By minimizing the reduction in ground contact pressure caused by a drooping wheel, this maximized traction on mild as well as serious terrain undulations.  The use of such soft springs (while retaining a 1600 lb payload capability) was made possible  by the Boge self-leveling strut (a self adjusting air spring) fitted to the central A-frame link on the rear axle.  This provides a restoring force on the center of the axle to compensate for load, allowing very low spring rates to be used at the road wheels. The Classic coil suspension was also designed to maximize available vertical wheel travel and articulation, keeping the wheels on the ground and gripping in terrain that has other 4x4s clawing at the air. This obviously helps both traction and control. More information on this topic is given below under articulation and ramp travel index.

The front radius arms are attached to the axle by two bushings each, giving the vehicle some additional roll stiffness due to the fact that these bushings must be deflected in order for the axle to tilt. This gives the front axle more lateral stability than the rear -- an important thing to remember when jacking up one end of the vehicle.  When fuel injection was introduced in 1984, efforts were made to reduce body roll to cope with the extra speed. The front radius arm bushings were stiffened up, and variable rate springs were used on the rear. In 1991, the suspension was re-tuned to further reduce body roll; this time the old bushings and springs returned but front and rear sway bars were added. Maximum articulation was unaffected.

                                                                               Approximate Coil Spring Rates (lb/in)     Sway Bars    Bushings
                                                                                      (Front)    (Rear)
Pre-EFI Range Rover 1970-84                                    133        150                                            no               soft
RR Base Models 1984-92, County 89-90                  133        120-178 (variable rate)          no                hard
RR County 1991-93                                                     133         150                                           yes               soft

 

Air Suspension Details

Overview
The electronically controlled airbag suspension used on late model Classics, the Range Rover P38 and the Mark III Range Rover gives the vehicle a low profile for high speed handling, fuel economy and safety, while allowing a higher clearance to be achieved for four wheeling. It also achieves the load leveling function by pumping air into the individual springs to maintain ride height and keep the vehicle on an even keel regardless of load.

The system uses air springs of the type used on large trucks, but specially designed by Dunlop for long travel. Air is drawn into a 10 liter storage tank through a dryer and compressor. System operating pressure is 10 bar (150 psi) for Classic and 4.0/4.6 models, and 13.7 bar (200psi) on the Mk III model. A solenoid valve block  regulates the flow of air to and from each individual spring under the control of the system ECU. All exhausted air passes out through the dryer in reverse to flush it out and avoid any water buildup in the bottom of the tank.

Height sensors for each wheel (potentiometers mounted on the suspension arms) inform the ECU of the vertical position of each wheel. 

Height Settings

1. Access Mode -- the lowest setting, 2.5 inches below standard ride height on the Classic and 4.0/4.6, and 1.8 inches (40 mm) on the Mk III. On the latter two models it can be "preselected" prior to stopping, and on the Mk II it can actually be activated when the speed drops below 15 mph.

2. Low Profile/Motorway -- an inch (0.8 inch or 20 mm on the Mk III) below standard; selected automatically above 50 mph (62 mph Mk III) unless inhibit switch is depressed.

3. Standard Height -- default position used in normal around-town driving.

4. High Profile/Off Road -- 1.6 inches above standard on  Classic and 4.0/4.6 models; 2.4 inches (front) and 2.0 inches (rear) on Mk III.

5. Extended Profile (Classic & 4.0/4.6 only) -- 2.8 inches above standard; selected by the ECU when it senses the vehicle is high centered.

Driver and Automatic Height Controls
Two dashboard switches provide manual control of ride height settings. There is an up-down rocker switch (replaced by a rotary control switch on the Mk III) and an "inhibit" switch (renamed the "hold switch on the Mk III and located at the center of the rotary control). The Mk III also has an additional switch on the driver's door that can be used to select access mode.

On the Classic and 4.0/4.6, all height settings except "Extended profile" can be selected manually using the rocker switch. The "Inhibit" or "Hold" switch can be used to lock the height setting in standard or low profile.  On the Mk III, the low profile /motorway setting cannot be manually selected, but once it is at this height it can be held there  by the "hold" switch.

The suspension ECU changes ride heights automatically under various conditions. In access mode, moving away from rest, standard ride height is automatically selected. At freeway/motorway speeds, low profile or motorway mode is selected automatically unless the inhibit/hold switch is activated. In High Profile/Off Road mode, if speed rises above about 30 mph (31 mph on the Mk III) the suspension reverts to "standard" height. On the Mk III, if the ECU senses that the trailer connector is being used, the suspension is locked into the "standard" height setting.

RR III ArticulatingLeft-Right Cross-Linking of the Suspension
On the Mark III Range Rover, with its independent suspension geometry, the above features are augmented by the use of large diameter air tubes linking the left and right sets of air springs at front and rear. Operation of the cross-linking is automatic only; when the air suspension ECU senses wheel movements corresponding to off-road conditions, valves in these cross linking tubes are opened, air can flow freely from left to right airbags. This equalizes pressure between the two, reducing the effective spring rate to zero. This is the ultimate in soft suspensions. If the left front wheel is raised, the right front one will be pushed downwards. This makes for greatly increased ground contact force (and traction) on a drooping wheel, as well as a very soft ride.

Benefits of the Air Suspension System
Obviously, the air suspension system conveys many benefits over an ordinary fixed coil or leaf suspension. The availability of an instant "lift" for off road operation is the main attraction of the system. However, the ability to lower the vehicle to access mode is particularly appreciated by short spouses and mothers.  Also, when the body is lowered from standard height to motorway or low profile mode, the springs are automatically stiffened slightly for better high speed control, the castor angle is increased for better directional stability (Classic and 4.0/4.6 models), and the profile of the vehicle is lowered for better stability and aerodynamics. On off pavement expeditions, vehicles are typically heavily loaded, and the ability of the air suspension to maintain constant height under all load conditions is a real boon. No sagging in the rear, or reduction in clearance. Also, the progressive nature of air springs reduces the chance of "bottoming out" when hitting a bump too fast. When towing, there is no need to use the tiresome and labor-intensive load equalizing hitches needed with all other vehicles.

More Details
For more detail on the air suspension, see the Air Suspension Operation, Diagnosis and Repair section of this website.

 

Advantages of a Soft Suspension for Four Wheeling

Until the 1990s, conventional and "lifted" 4x4s overwhelmingly used leaf springs or stiff coils with anti-sway bars tuned for flat high speed cornering on pavement or supposed "heavy duty" use off road. Aftermarket "upgrades" invariably included even stiffer springs, shocks, bushings and/or anti-sway bars. The net effect was a very stiff suspension that not only provided less maximum wheel travel (resulting in wheels lifting off the ground in very uneven terrain) but much reduced traction even in mild off-road situations requiring only modest vertical wheel movements. When a wheel droops even an inch or two on uneven terrain, its ground contact force is significantly reduced, reducing available traction.

As a hypothetical example, consider a 4,000 lb vehicle with 1,000 lbs supported by each wheel, encountering a small 4-inch mound under one wheel at low speed. That wheel and its diagonal opposite will be deflected upwards by 1 inch, while the other two will each droop by an inch.  Truck and 4x4 springs are commonly rated at over 300 lb/inch; with such a spring at each wheel, one inch of droop will reduce wheel loading by 300 lbs, reducing available traction at that wheel by 30%. (With an open differential on the axle, traction is lost at both wheels). In this simplified model, a moderate 8 inch terrain irregularity would reduce available traction by 60%.  The Classic Range Rover introduced the use of springs of about 150 lb/inch stiffness -- in our model this would reduce the traction loss to 15% for the 4 inch bump and 30% for the 8 inch bump.

The above example is oversimplified, but it illustrates the adverse effects of firm springs on off-road traction, even on moderate terrain. It explains the dogma that serious off-road vehicles must use "lockers" on the differentials to maintain traction. Lockers force both wheels to rotate at equal speed, transferring all the torque to whichever side has the grip. They therefore greatly increase stress on the drive train components, and have adverse side effects on steering control. The locker can suddenly transfer 100% torque to one wheel, breaking parts with notorious regularity.

These simple consequences of basic mechanics seem never to be learned by other 4x4 manufacturers. In recent years, however, aftermarket suspension builders have cottoned on to the advantages of soft, flexible suspensions, and some off-road suspension builders are even taking it to extremes, with suspensions that are so flexible that they are intended only for off pavement use and are unsafe to drive on the highway.

A significant side benefit of the Range Rover's soft "magic carpet" ride is its ability to run circles around other 4X4's on the typical rough road or trail, where stiffly sprung vehicles are reduced to a bone-jarring crawl. Not unimportantly, soft suspensions also Tread Lightly and result in less environmental impact.

 

Articulation and Ramp Travel IndexArticulation

Articulation is essentially the ability of the other wheels to stay on the ground when one wheel is lifted up (e.g. surmounting a rock). Articulation of an axle is measured as the difference in vertical position between one wheel and the other on the same axle. Total articulation (front plus rear) that the wheels are capable of represents the height of an obstacle that could be theoretically surmounted by one wheel while the others still remain on the ground.

In the early 1990s, Four Wheeler magazine introduced a measure of suspension articulation called ramp travel index (RTI). One wheel of the vehicle being tested is driven up a 20 degree ramp, and the distance it travels up the ramp before one of the rear wheels leaves the ground is measured. To arrive at the RTI, this distance is divided by the vehicle's wheelbase and multiplied by a thousand.  (Longer wheelbase vehicles therefore need more articulation to achieve a given score). Since the measure was introduced, Range Rovers and other Land Rover products have been easily the highest scoring stock vehicles tested. On the new Mk III Range Rover, front wheel travel was increased to 270 mm (10.8 inches) and rear wheel travel to 330 mm (13.2 inches).

The following approximate figures for total articulation and RTI puts the figures for Range Rovers and "Brand X" 4x4s in perspective:

            Vehicle                                                                            Articulation (front + rear)           RTI
2003 Range Rover Mk III (Independent, air)                               24 inches + tire comp            710 (estimated)
1994 Range Rover County (air)                                                   23 inches                                703
1992 Range Rover County (coils)                                               22 inches                                 670
1995 Range Rover 4.0SE (air, sway bar disconnected)          24 inches                                 670
1995 Range Rover 4.0SE  (air, stock)                                       22 inches                                 600
1993 Range Rover County LWB (air)                                         21 inches                                 588
1995 Land Rover Discovery                                                        20 inches                                 588
Land Rover Defender  (coils -- US spec)                                   19 inches                                 580

1996 Jeep Grand Cherokee                                                        15 inches                                 422
Jeep Wrangler YJ                                                                          12 inches                                 357

The advent of ramp testing was a useful innovation, but in an effort to outscore each other some people have taken their suspension flex to such extremes that the vehicle may be dangerous to drive on the highway. Some aftermarket suspensions claim as much as 40 inches of total articulation; driving one of these on the freeway would be interesting.

 

Suspension Mods  for Improved Pavement Performance

Four wheelers are always tampering with their suspensions and tires above all else. The stock RR suspensions are hard to improve upon, but that does not stop us from trying!

The most common mods available from nearly all aftermarket suppliers are "uprated" shocks. For example, Bilstein shocks and steering stabilizers are available for Classic and 4.0/4.6 Range Rover models. These are said to give better control and a slightly firmer ride. On the 4.0/4.6 the ride is, IMHO, already too firm, so going further in that direction may no be what you want. Ian Dugdale reports that Koni red or Special shocks (road, not sport) are a good compromise for the 4.0/4.6/P38; he reports they are valved similarly to the Bilsteins but are valved for comfort while incorporating a strong rebound which reduces sway. He notes they should be used on their softest setting, which is still "firm, and not for those who like to wallow!"

Poly bushings are also available from such makers as Iron man and Old Man Emu to replace the stock rubber bushings on Classics. Poly bushings are said to last longer and be more resistant to the omnipresent oil drips. They are also much easier to get on and off. However, some owners have found them to wear out very quickly on radius arm frame mounts. Also, most poly bushings are firmer in compliance than the stock rubber parts. Recently available, however, are softer versions with ratings closer to the stockers.

Aftermarket sway bar kits are also available to reduce body roll when cornering. For non-sway bar Classics, kits to convert them to 1991-onwards "County" spec (including new rear springs, front and rear sway bars, and recalibrated bushings) are available. For the 4.0/4.6, a rear sway bar kit is available since the stock vehicle does not have one.

In my own opinion, all these upgrades are good if you are trying to make your Range Rover handle more sportingly on the paved twisties, but the net results include a firmer (or even harsh) ride, increased resistance to axle articulation and a consequent loss of available off road traction. These effects can be as major or minor as taste dictates; however they are all a compromise and what you choose depends on how you want to use your Range Rover.

The Mk III air springs give the best of both worlds with a firmer ride on the highway and softer spring rates off road in high profile. Arnott Industries has now developed a Generation III air spring for the 4.0/4.6 models which emulates these Mk III design advantages, as well as providing longer travel.

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Suspension Mods for Improved Articulation

One of the purposes of suspension  lifts is often to increase articulation as well as raise the vehicle. Aside from lifting, however, there are other measures one can take to are also designed to increase available articulation.

Sway bar Disconnects and Removal
The opposite of the above modifications are those designed to limber up the suspension for better articulation and traction. Sway bar disconnects are becoming fairly common in the four wheeling community to reduce resistance to articulation. See the Sway Bar Disconnect page for various designs for both the Classic and 4.0/4.6 models. Atlantic British now sells a quick disconnect specifically made for the Classic. Another one made by Sun Performance Products could be adapted by your machinist to fit the front sway bar on Classic and 4.0/4.6 Range Rovers.  In all cases, it is recommended that the sway bar be reconnected when returning to pavement.

I long ago removed the sway bar from my 4.0SE; this definitely improves off road articulation and traction, but at the cost of somewhat more floppy handling on the highway (try at your own risk!!). However with the fitment of  Generation III Arnott air springs I was able to firm up the highway handling while retaining nice soft spring rates and easy articulation off road.

Articulation Kits
A rear drop kit for the Classic is available from Safari Gard which lowers the shock mounts about two inches to take better advantage of available travel, increasing the overall articulation. For the 4.0/4.6, Arnott has developed the Generation III air spring which offers 2-3 inches more extension than stock springs. If used in conjunction with a sway bar disconnect and/or longer shocks, noticeably better articulation is available.

Load-Carrying Spring Upgrades

People who really use their Range Rovers off road usually have them loaded fairly heavily; in this case it is worth considering uprated or taller rear springs to help keep the rear at the normal height (since it is usually the first part of the vehicle to make ground contact off road). Winfried Schoepf  had the problem of a sagging rear end and bad cornering behaviour at speed on his 1988 turbo diesel RR. After inquiry with several UK specialists he decided to fit a pair of special Range Rover rear springs used by UK police. As they drive with a fair load all the time, these springs were also just perfect for Winfried, who also carries quite some stuff all the time. In front, he fitted Discovery Diesel springs, which are a bit stiffer than the RR ones. After fitting the new springs, cornering was much improved, he could again view a mile back in the mirror instead of just 30 meters, and still the ride was comfortable as you expect from a Rangie. Gone were the nasty clonks when the axle hits the rubber stops. The secret seems to be the progressive characteristic of these rear springs, giving comfort under normal load but providing enough strength when compressed. The genuine parts he used are:

LHR NTC 8573 (RR classic, UK police model)
RHR NTC 8572 (RR classic, UK police model)

 

Suspension Lifts

The purpose of lifts is usually to fit larger tires so that more clearance can be obtained under the axles. At the same time, of course, more clearance is gained under the chassis, so approach, break over and departure angles are improved. If the lift is well designed, with appropriate changes in shock travel, bump stops etc, the lift can also increase articulation.

Simple lifts on Range Rovers usually consist of changing to longer and/or stiffer springs. Because of the radius arm design, this type of lift increases the castor angle slightly, making the steering more "twitchy" if not corrected.  Taller lifts may also make the drive lines steep enough to require lengthened or custom made drive shafts and/or CV joints to ameliorate vibration. The associated bigger tires demand lower gearing (but lower differential gears make the pinion weaker due to its smaller size); this in turn puts more stress on the axles which may need strengthening. Adding an axle truss will reduce the ground clearance which was the whole purpose of the original project. In other words, careful consideration of these snowball effects is needed before embarking on lift projects of more than 1-2 inches. For lifts under 2 inches, however, most people do not encounter many untoward side effects.

Spacers: Spacers to insert between the spring and the axle or chassis are made by Rovertym and Rockware. These can e used to raise ride height by small amounts.

OME Lifts: The most commonly used lift for Classic Range Rovers is the Australian Old Man Emu suspension -- consisting of longer, somewhat stiffer coil springs and matching shocks. Medium duty (1 inch) and Heavy Duty (2 inch) versions are available, as are matching OME shocks. This system is available from almost any aftermarket Rover parts source. With the 2 inch lift, it is advisable to install the OME front radius arm bushes at the same time -- these have offset centers designed to correct the castor angle. Greg Haugen has a good description of his installation of OME medium duty springs and Rancho 9000 shocks.

DAP lift: A spring set from DAP gives about an inch of lift with only a small stiffness increase.

Bearmach Lift: Brian Graftaas recommends the Bearmach Big Blue springs. A friend of his had them, and they were MUCH softer than Brian's OME setup. They gave him the lift, but because they were softer, he had much better upward articulation and a much softer ride. However, on the downside, they didn't seem to last as long and settled rather unevenly. He replaced his (after about 2 years) with OME MD.

Lifts using Standard Land Rover Springs: For those wanting to experiment with different springs on their Range Rovers, it is good to know that all Land Rover coil springs are interchangeable in terms of fit. There is a listing of Land Rover springs, part numbers, spring rates and lengths  done by the Land Rover Club of Luxemburg. One common approach for a soft 2 inch lift is to replace the standard 133 lb/in front springs with your rear springs (150 lb/in NRC4305 or 120-180 lb/in NTC3285). Then you can use rear Discovery springs (NRC 8044, 210 lb/in) on the back end to even it up. Larry Michelon used Bearmarch BA2103 springs in the rear, plus a half inch spacer to level the vehicle. I wanted to try the relatively long NRC4304 springs on the rear but sold my Classic before I had a chance. Andy Grafton lifted his suspension by using longer springs without changing shocks -- he found articulation appeared to remain the same but the vehicle is riding 2" higher on the shocks.

Strutmasters Lift Kits: In early 2006 Strutmasters came out with convenient 2 inch lift kits that can be used with coil-sprung Range Rovers and as coil conversions of air sprung Classic and 4.0/4.6 models. The complete kits with springs and lift blocks cost $495 for the Classic and $545 for the P38. For details and photos see the coil conversion page.

Safari Gard lifts: All the lifts above are in the one to two inch range; taller lifts are available from Safari Gard. These suspensions are designed for off road use only, and may involve the need for correcting other aspects of suspension and driveline geometry. Safari Gard lifts use  special long, soft springs to enhance articulation. For example, their Stage II kit gives a 3-4" of lift with high flex, and involves replacement of shocks, springs and bump stops along with extended brake lines. Their new 3 link front suspension allows much more free articulation of the front axle -- normally the stiffest on a Range Rover.

Air Suspension lifts: The air suspension offers a useful lift by itself in High Profile mode, and an often-forgotten advantage of this is the fact that the maximum lift is retained regardless of load, unlike coil spring lifts. Even more lift can be obtained by modifying the suspension electronics to facilitate manually selecting extended profile (see the Extended Profile Selector page).

Many people assume the air spring models cannot be lifted in the conventional sense. Of course this is not true. The new Arnott Generation III air springs with 2-3 inches more extension are ideal for achieving a moderate lift with no other mods except possibly longer shocks. For greater lifts, just as with coil springs, spacers could be placed 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 4.6 using these principles; a full description of his method is found on the Air Suspension Lifts page. 

Body Lifts: If the goal is to fit bigger tires, a body lift can provide the required clearance under the wheel wells without messing with the suspension. Ron Beckett reports that such lifts are not uncommon in Australia. Rangie Spares makes body lift kits in various sizes for Rangie Rover Classics. The seat mounts have to be extended under the floor, and problems may or may not be experienced with shift linkages depending on lift height. Also, you should note that bull bars, bumpers etc need modification to lift them up to the correct point on the body.
 

Other Suspension Modifications, Upgrades and Repairs

For more information on modifying both coil and air suspensions on Range Rovers, see Repair Operations and Mechanical & Electrical Upgrades, and our main Air Suspension Information page, where there is information on:
Air Suspension:
       Symptoms, Diagnosis, Field Recovery/Repair
         Changing an Air Spring
         Upgrading to Arnott Generation III Air Springs: firmer on hwy, softer off road and more travel
         Conversion to Coil Springs
         Disabling
         Emergency Bypass/Manual Operation of EAS
         Extended Profile Selector
         Lifting the Air Suspension
         MARS (Manual Air suspension Recovery System)
         Manual Pump-up of Air Suspension
         Replacement with Coil Springs
         Replumbing the Air Suspension for manual Pump-up
         Suspension Upgrade for Jeeps: Airock Air Suspension
         Sway Bar Disconnects for Range Rovers
Coil Suspension: Spring Replacement/Upgrades

 

 

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Page revised February 10, 2012