Thread: P38 Coil Suspension Conversion

While the subject has been covered a number of times in the past I decided to add my account to the forum to benefit anyone that is contemplating performing this conversion. While the superior comfort of the air bag suspension is not in question the objective of the conversion was to increase the reliability of the suspension of the vehicle for off road use and to that effect the air bag system was removed and coil springs fitted. Alan Bates' coil spring conversion article which can be reached from the following page (RockRover - P38 Range Rover Winch Bumpers and Sliders ) served as a guiding light for me when performing the conversion and I acknowledge his invaluable contribution. As the end result of the conversion is above the 2” maximum legal lift from standard please look at this as one mans account of work performed on his own vehicle, not a specific recommendation for your vehicle – you must make up your mind how much lift you choose to perform on your own vehicle.

Old Man Emu springs are fitted to the vehicle - OME 2761 on the front and OME 2764 at the rear mounted with Land Rover coil spring insolators between the spring and chassis. The reason for choosing those particular springs was to stay as close to the spring rate of the air bags as possible in order to retain the comfortable ride of the vehicle. While the spring rate is a bit higher than the spring rate of the air bag system the end result is a reasonably soft ride with good handling on road and good off road articulation.

In order to perform the conversion I purchased a coil spring conversion hardware kit (RCA2C4046AK) from British Parts of Utah (which came with instructions on how to perform the conversion) and consists of spring mounting adapters, spring seats and isolators and wiring and instructions on how to disable the EAS alarm. The components of the kit are made by Arnott Industries. The front springs are OME 2761 which are Medium-Duty springs with a spring rate of 200 lb/in and a length of approximately 395mm. The rear springs are OME 2764 which are Medium-Duty springs with a spring rate of 220 lb/in and an approximate length of 425mm.

The vehicle has stock bumpers front and rear and has been fitted with 1” spring spacers from Arnott Industries (Arnott part number: K-2257) that are bolted between the bottom spring seat adaptor and spring seat on the right hand front spring (to counteract for the weight of the steering box and battery on that side) and 1” spacers bolted between the bottom spring seat adaptor and spring seat on both rear springs for extra lift. The combination of springs and spacers gives a total suspension lift of 2.75” on the front and 3.5” on the rear. On my vehicle 2.75” is the maximum front suspension lift that can be achived without causing front driveshaft vibration using the original drive shaft.

Standard front shock absorbers (STC3672) are fitted to both rear axle and front axle in order to maintain the comfortable ride of the vehicle. The front shock absorbers are longer than the rear ones and are used at the rear to compensate for the extra lift. The front shock absorbers are fitted with a 75x75x5mm RHS extension between the bottom shock absorber mount and the front axle in order to maintain the suspension travel with the extra lift. Sway bar linkages are also lengthened 75mm to compensate for the added lift. Slight relocation of the brake lines and ABS sensor wiring was done in order to eliminate the possibility of damaging them under maximum articulation.

The results of the lift from ground to top of wheel well with different size tyres are approximately as follows:

Front: 255 65 16 = 34.5” / 265 75 16 = 36.5” / 285 75 16 = 37.5”
Rear: 255 65 16 = 35.5” / 265 75 16 = 37.5” / 285 75 16 = 38.5”

The end result meets all my expectations for suspension performance, safety and comfort of the vehicle.

Originally Posted by p38oncoils

Hi RR P38, I agree with load levelling as a bonus as well as a smooth ride but, in regard to off road driving - depending on your suspension setup - if you have standard suspension then there is limited suspension articulation in high setting and the ability to keep all four wheels on the ground which is of paramount importance is compromised. If you are in normal setting you will have articulation but you will lack ground clearance.

If on the other hand you have your airbag system lifted and recalibrated, along with a modified shock absorber and potentiometer setup, you will have the extra ground clearance and the articulation that is so important but you are still bound to the reliability issues that haunt the airbag system in this vehicle and continue to give it a bad name (whether we like it or not). I don't need to go into discussion of what those issues are – horror stories abound on the web if one cares to look for them.

I share your passion for the P38 and it is my opinion that it is one of the most – if not the most comfortable off road capable SUV available to mortals like us. Lifting and improving the articulation of the suspension makes a good off road capable vehicle a great off road capable vehicle regardless of whether the suspension is air bag based or coil spring based. It all comes back to what level of reliability one settles for. For me coil springs win on reliability.

Yeah.....i'd have to disagree with you on this one in numerous ways. Firstly in my opinion, and my opinion only, if converting to coils is your thing then don't settle for a Range Rover P38 but rather a series 1 or 2 Discovery which most models have the coils anyway and would be more up your alley in what your looking for as the airbags suspension (and i've said this before) is one of the main key features of why you or rather i chose the Range Rover in the first place. By doing my research found that the airbag suspension setup along with BeCM system reads and sensors the terrain by interacting with the springs, something you cannot do with coils as the suspension in a coil setup is working totally independant. Not only that, but your taking a step backward in off-road technology (bit like going from coils back to leaf springs). As far as reliability is concerned, airbag springs are only going to be as reliable as either yourself or your mechanic is willing to thoroughly inspect them properly upon your regular service interval. Ignore it, and like everything else, they will fail at some point. I might add coils are really no different, they too suffer from metal fatigue and prolonged sagging over time, and like airbags, they too need regular inspection. As someone else here on AULRO mentioned, airbags are now very commonly used not only in modern 4WD's but truck, buses & cars that are either towing or hauling heavy weights, so they're not uncommon, just different that's all. And as far as flexiblity is concerned, i run stock standard airsprings on mine, and they still out flex your typical japanese 4WD in more ways than one. Running over 2 inch lift might sound ok to you, but i reckon your insurance company would want to keep a close eye on you as that's above the legal limit within most insurance guidelines and you may find yourself driving uninsured unless going with a specialist insurance mob.

Look these are really only my opinion on this subject and that's all, but you really shouldn't believe everything you hear about the horror stories in regards to the P38 Range Rover & the airbag suspensions, cause as i said before, they're only as good as your prepared to maintain them. I personally have admired the Range Rover P38 for what they are, and respect the fact that they're not called 'King of off-road' or ' the most capable 4x4' for nothing.