Continuing our first look at the new ARB BP-51 Suspension System, Main Line Overland received the first Jeep JK BP-51 kit on the East Coast, which we promptly mounted onto the MLO Rubicon. For this application, the BP-51 comes as a shock-only system due to the factory solid axle design of the Jeep JK (see our Land Cruiser 200 series review for the Coilover BP-51). We are told that BP-51 shock and spring kits are on the way using ARB's line of coil springs, but for now we are interested in this newest element of ARB's suspension line-up, which comes as a 4" front and rear shock that works with systems from 3 - 4.5" of lift. Systems with 2" and 3" of lift are forthcoming for those who want the BP-51 performance and adjustability with less lift. The MLO Rubi previously strode atop the AEV/ Bilstein 5160 shocks as part of AEV’s 3.5” Dual Sport RS Kit, a worthy system for many overland adventures, but there are some noticeable differences between the old and new set-ups, primarily in the adjustability of the BP-51, but also in the diameter of the shock shafts both front and rear, and the diameter of the top mounting bolts. Having a steel body and lower mount, the Bilstein can get away with a smaller amount of material and bulk, but the BP-51 fills out it’s larger anodized aluminum shock body with a 51mm shock piston, an internal fluid bypass system, and a CNC machined, hard-anodized lower mount. Unlike it’s coilover brother for the Land Cruiser, the JK shock does not have adjustable spring pre-load, but can be set to the vehicle load with the multiple spring rates available in ARB's coil springs.
A good suspension system should fit like a good suit--tailored to height and weight, and chosen with the occasion in mind. As an off-the-rack system, the ARB BP-51 has an obvious advantage in initial quality and adjustability, giving it an inside line as that favorite suit, however also at a higher cost per corner than non-adjustable shocks. For the Jeep, the BP-51 delivers a conveniently placed remote reservoir to improve cooling and resistance to fade, as well as on-vehicle-adjustable compression and rebound dampening using the included adjustment tool. ARB sees the BP-51 as their entry into a racing-type suspension application that can still work with the vehicle’s OEM geometry, and is backed by ARB's reputation for Outback-proven durability. The BP-51 shocks and struts come with a 3 year warranty (in contrast, AEV offers a 1 year warranty), and are also rebuildable, so that initial purchase has the potential to go a long way.
MLO gave the BP-51s the weekender test at the recent Jeep All-Breeds Festival in York, PA. Our Jeep Rubicon runs an AEV JK Premium Front Bumper, Warn 9.5cti Winch w/ synthetic line, sliders, AEV JK Rear Bumper/ Tire Carrier, Gobi Stealth roof rack, dual batteries, sPod, ARB Compressor, ARB 50qt fridge with slide-out tray, and a few other bits and bobs, so we set the damping at the softest position of the “heavy weight” setting per the recommendations in the ARB manual. At the time of testing, the Rubi was still running the AEV springs from its previous AEV 3.5” Dual Sport RS Kit to isolate the shocks as the point of comparison. Right out of the gates, we noticed the greater control in weight transfer, free of the wallowing in corners so often experienced with the previous set-up. Highway ride was smooth on the flat stuff, and on rougher sections of country road the shock firms up on deep compression, providing good bottoming resistance over slow and high-speed bumps. For a vehicle running heavy loads or a trailer, the adjustability of the BP-51 system can’t be understated. Even towing an AT Chaser, the Rubi maintained a comfortable level of damping. The rebound and compression collars are located at the bottom of the shock body, so at the trailhead we were able to dial the adjustable rebound and compression collars with ARB’s spanner tool during the course of a normal air-down. It is easy to see how this dampening adjusting process will integrate into the normal air-down/ air-up routine during combination on/off-road travel.
Since the AEV Dual Sport kit does not include an option for different spring rates, the next stage would be to weigh out the Rubi and get the proper ARB spring for its vehicle load. Look for this follow-up in the near future as the MLO Rubicon's overlanding set-up continues to evolve.
We are excited to see if the emergence of the BP-51 system ignites a shock war between AEV and ARB, or if AEV will counter by developing their own adjustable shock set-up. While the longevity of the more sophisticated ARB system remains to be seen, especially in America’s rust belt (Pennsylvania winters have dealt corrosive death to many a four-wheeler), for now, it is point ARB as they have thrown down the gauntlet in the overlanding suspension game. MLO has BP-51 suspension systems in-stock and ready to install, so come by the shop today for look-see.
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