2026 Forest River XLR Boost366BX

The XLR Boost 366BX leaves Forest River's factory at 13,074 lbs dry with 5,300 lbs of cargo capacity. Forest River publishes no GVWR for this line, so the loaded rating is not quoted on this page and is not computed from the other two figures. What the cargo number covers is defined by the factory: fresh water, gear, food, batteries and every dealer-installed accessory come out of it. Fresh water is 8.3 lb per gallon, so filling the 150-gallon fresh tank spends 1,245 lbs of the 5,300 lbs before anything else goes in.

Pin weight is 3,220 lbs, 25% of the dry weight as published; it rises as the trailer is loaded and comes off the truck’s payload, not its towing rating, so check it against the payload on your own door sticker (pin weight and payload).

Off hookups: 154 gallons of grey and black capacity against 150 gallons of fresh water, so fresh water runs out first (tank sizes by length).

Against the rest of the XLR Boost fifth-wheel roster this is the 5th of 5 fifth wheels by dry weight, in a line that runs from 9,094 lbs to 13,074 lbs. It is the heaviest fifth wheel in the line, so the tow vehicle should be settled before the floorplan is.

Plan the tow on loaded weight, not the 13,074 lbs dry figure: half the published cargo capacity brings this plan to about 15,724 lbs. Forest River publishes no loaded rating for this line, so the ceiling is the one on the trailer’s own weight label (how to read trailer weights).

Forest River’s line listing and this floorplan’s own factory page agree on all 4 shared figures. No GVWR is published for this line, so dry plus cargo has no rating to check against. A missing row means Forest River does not publish that figure (how figures are verified).

Forest River publishes no floorplan description for this plan in the channel this page is built from - only the numeric specification block. Rather than describe a layout from the floorplan code, which would be a guess dressed as a fact, this page carries what the factory publishes and says where it stops. 366BX is a XLR Boost designation and this site does not decode it into a layout claim.

How the 366BX differs from the other four XLR Boost fifth wheels. Most distinctive first. Sibling pages may cover other model years than this one (2026). How these ranks are worked out.

• Dry weight, 13,074 lb: heaviest of five; next is the 363BX (12,064 lb).
• Cargo capacity, 5,300 lb: largest of five; next is the 310BX (5,191 lb).
• Pin weight, 3,220 lb: heaviest of five; next is the 363BX (2,795 lb).
• Pin weight as a share of dry weight, 24.6%: largest of five; next is the 310BX (23.5%).
• Exterior height, 13 ft 6 in: tallest of five; next are the 310BX, 363BX and 375BX (13 ft 5 in).
• Length, 43 ft 6 in: second-longest of five, between the 363BX (40 ft 6 in) and the 375BX (45 ft 3 in).

Next to the 363BX, the nearest lighter floorplan by dry weight, the 366BX is 1,010 lb heavier by dry weight, has 569 lb more cargo capacity, has a pin weight 425 lb heavier, is 3 ft longer and stands 1 in taller; the two publish the same fresh tank, grey tank and black tank.

XLR Boost is the hardest of Forest River's toy-hauler rosters to read from the outside, for two reasons. It mixes classes: three published floorplans are XLR Boost travel trailers at 6,758 to 8,393 lb dry with 1,175 to 1,500 lb on the tongue, and three are XLR Boost or XLR Boost X fifth wheels at 9,094 to 13,074 lb dry with 2,090 to 3,220 lb on the pin. And Forest River publishes no GVWR for any of the eleven plans, so the loaded figure that determines whether a given truck can legally tow a given plan is not available from the factory in this channel. Cargo capacity is published, 2,507 to 5,300 lb, and dry weight is published, so what the roster tells you is what the trailer weighs empty and how much it will carry - not what it may weigh when full.

A full 150-gallon fresh tank is about 1,245 lb of water, 23% of the 366BX’s 5,300 lb cargo capacity, leaving 4,055 lb. Across 5 XLR Boost fifth-wheel floorplans the water share runs 17% to 27%, and 3 give up more than this one. Nearest on that share: XLR Boost 286B at 17% and XLR Boost 310BX at 24%.