4WD MODIFICATIONS - SUSPENSION & BRAKES
Bilstein shock absorbers are well known for their high-performance damping abilities on 4WDs and there’s a revalved range to suit single and dual mounting on caravans and camper trailers.
The engineering team at Sydney’s Heasman Steering & Suspension has been working on suspension improvements for vehicles in towing applications, including a new range of Polyair air-assist, rear spring kits for 4WD utes.
At OTA we’ve been evaluating Polyair air bellows assist springs on the back of our Project 75 ute and we’re very impressed with their performance, in conjunction with Bilstein dampers all around. When the ute is unladen we run only 35kPa (5psi) in the rear air springs and when our slide-on camper is in place, or when we’re towing a trailer with a heavy ball weight, we up the pressure to 210kPa (30psi).
Our testing confirms that the Bilstein/Polyair combination handles maximum-GVM and GCM loads without any problems. The OTA ute has kept running over corrugated surfaces when less-equipped vehicles have needed a stop to let their shock absorbers cool down and recover some damping performance.
The latest Polyair kits from HS&S for the rear axles of popular 4WD utes are ‘no-drill’ designs that simply clamp in place. Extensive testing, including a final real-world test at Cape York, confirmed that the clamping system is effective and durable, and doesn’t work loose under extreme rough-road and off-road conditions.
In parallel with this development the company has been working on new valving for its Bilstein shock absorbers, making them ideal for trailer applications. Many on-road and off-road caravans and camper trailers are fitted with independent coil-spring suspensions and high-performance shock absorbers are vital for optimum suspension behaviour in these systems.
With older-style leaf-spring trailer suspensions that had some inherent damping it was possible to get away with cheap shock absorbers, but taper-leaf, coil or torsion bar suspensions need fast-acting, fade-resistant damping to control wheel movement.
Bilstein shock absorbers with optimised trailer suspension valving are now available.
HS&S testing of its off-road caravan shock absorbers culminated in a Cape York trip that took in plenty of corrugations and off-road driving. Check out the video: