To gain greater clearance and load-carrying ability, I pulled the factory coils and replaced them with Old Man Emu heavy-duty coils. The Old Man Emu coils gave me 2 inches of additional height and several hundred pounds more of load-carrying ability. My current springs can handle the greater load, both vehicle weight and gear. Taller springs require taller shocks, so I replaced the factory shocks with Old Man Emu LTR shocks, which feature a separate reservoir that doubles the oil capacity of each shock. The greater surface area added by the reservoir and the increased oil volume prevent shock fade on long trails. The LTRs are also valved to match the spring rate on the Old Man Emu coils.
Taller springs and increased shock travel necessitate longer brake hoses. I have seen a few trucks where the brake hoses were the limiting factor in their suspension travel. Obviously, this is not a good thing. I replaced my factory rubber brake hoses with Expeditionware stainless braided hoses that are 3 inches longer than stock. The Expeditionware hoses are covered with a clear plastic sleeve to prevent debris from working its way in and deteriorating the stainless braiding's integrity. On top of the clear plastic sleeve is a black plastic spiral that prevents the longer brake hoses from contacting other suspension pieces and becoming abraded.
The overall appearance of this 90 remains stock-looking, although the vehicle is far from stock.
The coil spring, shock, and brake hose changes are basically the only changes I've made to my vehicle's suspension system. The lift is not so tall as to require driveshaft or suspension geometry changes, and the vehicle's overall reliability is not compromised in any way. In fact, I believe the Old Man Emu LTR shocks and Expeditionware brake hoses are substantially stronger and more reliable than their corresponding factory components. Furthermore, all of the suspension mods are reversible if I change my mind or something better should come along. All of the factory mounting points are unchanged, so I can locate replacements easily if I should be unfortunate enough to break a suspension component far away from home.
Lifting a vehicle usually results in fitting larger and more aggressive tires. I chose to increase the reliability of my vehicle in the process. Factory Defender 90s came fitted with BFG All-Terrains in 265/75 size. The All-Terrains are excellent tires, but I wanted something taller and more suited to my specific needs so I replaced the All-Terrains with Michelin XZLs in 8.25 R16 size.
The Old Man Emu suspension provides greater flex than factory but was not chosen for flex but greater load-carrying capacity and off-highway performance.
My XZLs are just shy of 34 inches tall, but they are very skinny to permit full tuck into my wheelwells without any trimming. The XZLs are also very strong tires, having four steel belts beneath the tread and a steel-belted sidewall. Ninety-percent of your trail fixes will involve the tires, so having strong ones greatly enhances your vehicle's overall trail reliability. The XZLs are not as pliable and grippy on the trail as other tires, but I accept that in order to gain greater strength. To increase wheel reliability further, I replaced the alloy factory wheels with Land Rover steel wheels. The steel wheels are stronger than the alloy wheels and may be pounded back into shape with a hammer if bent on the trail.
Just as with the suspension, the larger and heavier wheels necessitated some other mods to maintain driveability and reliability. The taller wheels required regearing to maintain engine performance. The factory ring-and-pinions on Defender 90s are 3.56-ratio. I replaced these gears with 4.11 to maintain driveability on the road and trail. The larger wheels also reduce braking efficiency, so I replaced the factory brake rotors with drilled and slotted versions from Disc Brakes Australia (DBA). My truck still does not drive like a factory Defender, but it does drive better than if had I not made these changes.