BILSTEIN SUSPENSION ROADTEST
5,000 kilometres of rough, loaded 4X4 touring put these shock absorbers through the ringer.
Last Updated: 6 March 2022
Before taking off on a big trip in Project 130, I had some new suspension installed to replace the old, original and worn-out gear. My shocks looked to be OEM, and probably 15 years old.
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Along with King Springs that had different lengths and rates to the stuff I removed, I got some new shocks under the old girl as well: Bilsteins were chosen, because of the solid reputation of the brand, and discussions I have had with others who have used them in 4X4s previously.
The new shocks were on the car for less than a week, before it was loaded up and pointed toward the Australian interior. During that time, I have to say I relished the refreshed drive that the 130 had with the new gear. These things aren’t exactly drivers’ cars on the bitumen – but the car felt much more composed and responsive with the new spring and shock combination underneath. Probably the best improvement was control over small bumps and undulations; feedback through the steering wheel lessened noticeably, as did that jiggling, side-to-side feeling.
But, on-road performance for me plays a close second fiddle to how these things go off-road. I’m not one to pretend I’m racing in the Baja 1000 on desert trips, going through rough country at high speeds. Accuse me of needing a zimmer frame … but what I look for in a shock is something that lasts the distance, and can put up with big loads and constant suspension cycling and do a good dampening job in the meantime.
To get to the point, we fitted the Bilstein B6 Offroad shocks to my Defender 130, loaded closely to its 3.5 tonne GVM, and did some driving. We headed out from Sydney to Broken Hill, and then turned north at Peterborough.
We travelled the Oodnadatta Track, following the Old Ghan up to Old Andado, then turned right and did the Madigan Line. We went via Geosurveys Hill to Birdsville, and kept going with a run down Cordillo Downs Road and the Old Strzelecki Track. Then we finished with a run through Cameron Corner to Bourke and finally back to Sydney. We didn’t kill the shocks. On the contrary, they still perform as adeptly on-road after the big trip as they did before. For me, that’s a win.
Driving to the conditions, I didn’t experience any fade during the trip. The shocks look to have taken knocks big enough to remove a good amount of that yellow paint – but the bodies and mounting points of the shocks proved stout enough to endure the punishment.
Using the friction of oil passing through internal valves, the shock absorber aims to control the movement of the spring. It does this by turning kinetic energy (movement) into thermal energy (heat); stopping the bouncing effect of the spring. Conversely, that generation of heat is something that can negatively affect the performance of a shock, and cause it to fail. The harder it is working, the more heat it generates – affecting the oil’s viscosity (thickness) and cavitation, and performance of the seals within the unit.
To look at some specs, the Bilstein B6 Offroad is a monotube shock absorber, with pressurised nitrogen gas inside of the shock in a separate chamber, which prevents the shock oil from cavitating (foaming) when under the duress of temperatures as it is forced back and forth through the valves, thus reducing the impact of heat on performance. The piston is 46mm, working with ‘shim stack’ valves to control the flow of oil in the shock absorber. With this setup, the Billies are rebuildable (and they can have their dampening rates adjusted by the right workshop). Also, the shocks can be mounted upside-down, without an impact on performance.
After my run with them, I can’t see a reason not to recommend them.
Prices start from $396 per pair.
By Sam Purcell
