Coil Replacement Kit for Mercedes W639 series Viano 2003-2014

No. A Boss Load Assist kit does not increase your GVM. It supports and levels the vehicle within the factory limits so it sits and tows correctly, but the legal carrying capacity is still set by the vehicle’s original GVM and rear axle ratings.

On vehicles, Boss Load Assist kits are plumbed as a dual-path system so the left and right airbags cannot transfer air between them. This stops the vehicle leaning or feeling unstable in corners. Linking left and right together allows air to move from the loaded side to the unloaded side, which can cause body roll and poor handling.

Yes, but the setup depends on your lift height. Standard 2500 or 2600 double-bellow bags work on stock height and lifts up to around 2 inches. For more than 2 inches of lift you generally need triple-bellow bags (2503 or 2603) and/or different brackets or spacers. The best approach is to measure the gap at the bump stop at your desired ride height and confirm the correct kit with Boss.

LA Clearance kits are standard Boss Load Assist kits that may have minor cosmetic marks, small scratches or packaging damage. The structural components, testing, performance and warranty are the same as the non-clearance kits. They are simply offered at a sharper price because they are not cosmetically perfect.

Yes, provided you stay within the same airbag series. For example, if your kit uses 2500 airbags and you add more than 2 inches of lift, you can normally upgrade to 2503 triple-bellow bags that suit the same bracket pattern. Airbags from different diameter series (e.g. 2400 vs 2500 vs 2600) are not interchangeable unless the kit is specifically designed for that change.

Boss airbags are manufactured using a proprietary blend of cured natural rubber, hi-tensile steel cords and ballistic reinforcing. They are independently tested to a recommended test pressure around three times the maximum working pressure, and burst-tested even higher. In load assist applications it is virtually impossible to pull the bag apart from the bracket because the bead is clamped by a solid aluminium ring, rather than relying on crimped plugs.

Boss airbags are attached to the mounting brackets using an aluminium clamping ring that acts like a beadlock. The ring clamps the bead of the airbag directly to the steel plate so the bag is mechanically locked in place. Many other brands, including big names like Firestone and Dunlop, use plastic or metal end plugs crimped into the bellows. Under extreme droop (for example on a hoist or heavy articulation), those plugs can be pulled out of the bag. With the Boss beadlock-style design, the bag cannot be pulled off the mounting plate in normal service.

Most competent DIYers can install a Boss Load Assist kit with basic tools in 2–3 hours. The brackets are vehicle-specific and generally bolt to existing chassis points. You need to be comfortable working safely under the vehicle, routing airlines away from heat and moving parts, and setting basic alignment. If in doubt, a suspension or 4x4 workshop can fit the kit for you.

Do not run the bags completely empty. A minimum of around 5–10 psi is recommended when the vehicle is unladen. This keeps the bag in shape and protects it from pinching or chafing under full articulation.

The Coil Replacement Kit is designed to replace the factory rear airbags in the Mercedes W639 series Viano (2003-2014). This kit provides enhanced stability and load support, ensuring the vehicle maintains a level ride height when loaded.

This kit is suitable for standard height applications and can accommodate a lift of up to approximately 2 inches. For lifts greater than 2 inches, additional modifications may be necessary.

Yes, the Coil Replacement Kit can be used in conjunction with other suspension modifications, such as upgraded shock absorbers or additional lift kits. However, it is essential to ensure compatibility and proper installation to maintain vehicle safety and performance.

While experienced DIY enthusiasts may install the kit, professional installation is recommended to ensure proper fitment and alignment. This helps to maximise performance and safety while minimising potential issues during use.