The Ultimate Touring Upgrade: Milwaukee Twins 6 Gallon Extra-Capacity Tanks

For the rider who believes that the road should never end, fuel capacity is the ultimate limiting factor. The Milwaukee Twins Extra-Capacity Fat Bob Gas Tanks are designed to push those limits further than ever before. Specifically crafted for the 1984–1999 Harley-Davidson Softail era, these tanks offer a staggering 6-gallon total capacity. This is a significant 20% increase over standard 5-gallon Fat Bob tanks, making them the premier choice for cross-country travelers, rally-goers, and anyone who demands maximum range from their Evolution-powered machine. With these tanks, you can confidently navigate the loneliest stretches of highway, knowing you have the fuel reserves to reach the next horizon.

Iconic Fat Bob Styling with a Muscular Stance

Despite the massive increase in fuel volume, Milwaukee Twins has maintained the legendary “Fat Bob” silhouette that has defined Harley-Davidson cruisers for generations. These tanks feature the classic split-tank design and flatside mounts, ensuring they sit correctly on your 1984–1999 frame. The extra capacity is achieved through a slightly wider and deeper profile, which gives your Softail a muscular, powerful stance that looks particularly impressive on Fat Boy (FLSTF) and Heritage (FLSTC) models. By filling out the area around the frame backbone, these tanks create a seamless, integrated look that enhances the bike’s overall presence without compromising its vintage soul.

Premium Construction for the Long Haul

Milwaukee Twins is known for “no-nonsense” quality, and these tanks are built to endure the rigors of high-mileage riding. Constructed from heavy-gauge, deep-drawn steel, the tanks feature precision-welded seams and reinforced mounting tabs to handle the extra weight of six gallons of fuel.

• Fitment: Fits 1984–1999 Softail models and 1985–1986 FXWG (4-speed Wide Glide) models.
• Hardware Support: Designed to accept a 22mm external thread petcock on the left side.
• Gas Cap Style: Utilizes dual 1983-up screw-in style gas caps for a secure, modern seal.
• Instrument Integration: These tanks are designed to accept most stock-style dash assemblies and speedometers, keeping your cockpit functional and familiar.

Preparation and Custom Finish Guidelines

These tanks arrive in a raw, unpainted steel finish, providing a perfect canvas for your custom paint vision. Because of the large surface area, they are ideal for elaborate custom graphics, pinstriping, or deep, lustrous solid colors. As with all high-quality aftermarket steel tanks, proper preparation is the key to a lifetime of service. We strongly recommend that the tanks be pressure tested and internally treated with a high-quality tank sealer before painting. This step is crucial for protecting the interior from the corrosive effects of modern ethanol fuels. Additionally, because these tanks are wider than stock, we suggest a “dry fit” on your frame to check for clearance against your handlebars, triple trees, and seat before proceeding to the paint booth.